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					                                         GLOBAL STANDARD




Master Document:              Global Heat-Treat Standard

Standard No.:                 GS-0062            Revision level: A          Revision date: 2006-10-24

Author:                       David Wills

Process owners/               Greg Shen, Milan Sukovsky, Tom Loegstrup, Patrick Bicard, Roman
Reviewers:                    Torbus, Stanislawa Wontor, Wilfried Weiss, Wilhelm Lindert


Administrator:                Christine Holst

Approved by:
                              Doug McCoy                                   Date: 2006-10-26
(Process owner)




Local Edition:

Language:

Author:

Process owners/
Reviewers:

Administrator:

Approved by :                                                              Date: (YYYY-MM-DD)




Auxiliary tools:




Changes in relation to previous issue are written with red, alternatively for figures and tables with a red frame around.




GS-0062.A                                                                                                     Page 1of 22
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 1   CONTENTS
     2.  Scope
     3.  Purpose
     4.  Related Documents
     5.  Equipment and Pyrometry
     6.  General Heat-Treat Requirements
     7.  Through-Hardening
     8.  Gas Carburizing
     9.  Gas Nitriding
     10. Carbonitriding
     11. Gaseous Nitrocarburizing
     12. Salt Bath Nitrocarburizing
     13. Induction Hardening
     14. Hydrogen Embrittlement Relief
     15. Heat-Treat Personnel Qualifications
     16. Testing Requirements
     17. Test Report Requirements
     18. General Operating System Requirements
     19. Appendix A: General Notes
     20. Appendix B: Thickness Limits for Surface Hardness Measurements of Surface Treated
                       Materials
     21. Appendix C: Case Depth Determination According to DIN 50190
     22. Appendix D: Chart Showing Visual Estimation of Per Cent Retained Austenite

 2   SCOPE
     This standard establishes general requirements for heat treatment of steel parts by Sauer-
     Danfoss heat-treat sites and Sauer-Danfoss suppliers and forms an integral part of Sauer-
     Danfoss detail specifications and engineering prints. When there is a conflict between this
     standard and the detail specification or the drawing, the drawing shall take precedence first
     and the detail specification second. Global standards for SQA’s, PPAP’s, and PFMEA’s
     are an important and integral part of high quality heat treatment, but are not within the
     scope of this document.


 3   PURPOSE
     This standard specifies the minimal requirements for inspection methods, process
     controls, heat-treat equipment, and general operating procedures necessary to produce heat
     treated parts free from defects. This standard is intended as a supplement to the industry
     standards referenced throughout this document. As a standard, the practices defined in
     this document should be considered as requirements for Sauer-Danfoss and external heat
     treating facilities. In cases where a U.S. standard is specifically cited, an equivalent
     European standard may be substituted.




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  4     RELATED DOCUMENTS
        The following documents are referenced herein:
        SAE and AMS Publications are available from SAE, 400 Commonwealth Drive,
        Warrendale, PA 15096-0001.
        ASTM Publications are available from ASTM, 100 Barr Harbor Drive, West
        Conshohocken, PA 19428-2959.

        ASTM E384        Microhardness of Materials
        ASTM E10         Brinell Hardness of Materials
        ASTM E18         Rockwell Hardness and Rockwell Superficial Hardness of Metallic
                         Materials
        ASTM E92         Test Method for Vickers Hardness of Metallic Materials
        SAE J423         Case Depth Measurement
        AMS 2759C        Heat Treatment of Steel Parts (General Requirements)
        AMS 2759/1       Heat Treatment of Carbon and Low Alloy Steel Parts -
                         Minimum Tensile Strength Below 220 KSI (1517 Mpa)
        AMS 2759/2       Heat Treatment of Low Alloy Steel Parts - Minimum Tensile Strength
                         220 KSI (1517 Mpa) and Higher
        AMS 2759/6       Gas Nitriding and Heat Treatment of Low Alloy Steel Parts
        AMS 2759/7       Gas and Vacuum Carburizing and Heat Treatment of Carburizing –
                         Grade Steel Parts
        AMS 2759/9       Hydrogen Embrittlement Relief (Baking) of Steel Parts
        AMS 2757         Gaseous Nitrocarburizing
        ARP 1962         Training and Approval of Heat Treating Personnel
        AMS H 6875       Heat Treatment of Steel Raw Materials
        AMS 2750         Pyrometry
        ARP 1820         Chord Method of Evaluating Surface Microstructural Characteristics
        SAE J864         File Hardness Measurement Method
        ASTM E1417       Standard Practice for Liquid Penetrant Testing
        ASTM E1444       Standard Practice for Magnetic Particle Testing
        ASTM E709        Standard Guide for Magnetic Particle Examination

        In addition to the standards specifically referenced by this document, sections 4.1 – 4.5 of
        this document serve as a cross-reference by heat-treat process of the U.S. and European
        industry standards.


4.1     General Heat-Treat Requirements

        Process          Description of the Standard           ASTM/SAE/AMS/             DIN/EN/ISO
                                                                   ARP Nr.                   Nr.
      General Heat       Heat Treatment of Steel Parts            AMS 2759               DIN 6773/1-5
       Treatment

                           Practice of Heat Treatment                AMS 2759             DIN 17022-1

                     Heat-Treat Processes of Iron Materials          AMS 2759             DIN 17014-3



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4.2     Heat-Treat Equipments
        Process        Description of the Standard         ASTM/SAE/AMS/   DIN/EN/ISO
                                                               ARP Nr.         Nr.
      Heat-Treat     Industrial Temperature Uniformity        AMS 2750      DIN 17052
      Equipment                 Requirements                                DIN 16160

                    Flame Control with Gas Equipment                         DIN 3258

                          Industrial Quench Oils              AMS 2759       ISO 9950

                                Pyrometry                     AMS 2750      DIN 24201

4.3     Heat-Treat Processes
       Process         Description of the Standard         ASTM/SAE/AMS/   DIN/EN/ISO
                                                               ARP Nr.         Nr.
      Harden and    Heat Treatment of Carbon and Low          AMS 2759-1    DIN 17022-1
      Tempering          Alloyed Steel Parts below
                             220KSI/151MPa

                    Heat Treatment of Low Alloyed Steel      AMS 2759-2     DIN 17022-1
                       Parts below 220KSI/151MPa

                    Heat Treatment of Steel Raw Material     AMS H 6875     DIN 17022-1


                         Practice of Heat Treatment           AMS 2759      DIN 17022-1

                        Heat-Treat Processes of Iron                        DIN 17021-1
                     Materials Assortment Based on the
                               Harden-ability
      Carburizing    Gas and Vacuum Carburizing and          AMS 2759-7
                    Heat Treatment of Carburizing Grade
                                 Steel Parts

                        Heat Treatment Carburizing                          DIN 17022-3
       Nitriding    Gas Nitriding and Heat Treatment of      AMS 2759-6
                         Low Alloyed Steel Parts

                         Gaseous Nitrocarburizing             AMS 2757      DIN 17022-4
   Inductive           Surface Hardening Treatment                          DIN 17022-5
   Hardening
 Heat Treatment           Heat Treatment of Tools                           DIN 17022-2
    of Tools
 Documentation       Technical Product Documentation                         ISO 15787
                        Heat Treated Ferrous Parts




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4.4   Test Requirements
      Process        Description of the Standard         ASTM/SAE/AMS/           DIN/EN/ISO
                                                             ARP Nr.                 Nr.
 Macro Hardness     Standard Test Method for Brinell        ASTM E10             EN 6506-1,2,3
  Measurement        Hardness of Metallic Materials

                   Standard Test Method for Vickers           ASTM E92           EN 6507-1,2,3
                     Hardness of Metallic Materials

                    Rockwell Hardness and Rockwell            ASTM E18           EN 6508-1,2,3
                    Superficial Hardness of Metallic
                                Materials

 Micro Hardness    Evaluation of the Case Depth after     ASTM E384, SAE J423,    DIN 50190-2
  Measurement              Surface Hardening                  ARP 1820

                   Evaluation of the Case Depth after     ASTM E384, SAE J423,    DIN 50190-1
                              Carburizing                     ARP 1820

                   Evaluation of the Case Depth after     ASTM E384, SAE J423,    DIN 50190-3
                               Nitriding                      ARP 1820

                  Evaluation of the Case Depth of Case        ASTM B721           DIN 30911-5
                       Hardened Powder Material                                  DIN ISO 4507
                                                                                 ISO 4498/2/00

 Special Checks       Magnetic Particle Inspection       ASTM E1444, ASTM E709 DIN/EN/ISO 3059
                                                                                  EN 571-1

                        Liquid Penetrant Testing             ASTM E1417          DIN/EN 3452

                               Pyrometry                      AMS 2750

                  Chord Method of Evaluating Surface          ARP 1820
                    Microstructural Characteristics

                  Microscopic Examination of Carbide                               SEP 1520
                    Structure in Steels by means of
                            Diagram Series

                    Hydrogen Embrittlement Relief            AMS 2759-9
                        (Baking) of Steel Parts




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4.5     Education and Training
        Process          Description of the Standard          ASTM/SAE/AMS/            DIN/EN/ISO
                                                                  ARP Nr.                  Nr.
       Education        Training and Approval of Heat            ARP 1962
      and Training            Treating Personnel

                          Heat-Treat Processes of Iron                                    DIN 17023

                        Materials Forms and Heat-Treat                                    EN 10052
                                  Instructions

                     Items of Heat-Treat Processes of Iron                                DIN 17014
                                   Materials

                       Ferrous Products Heat Treatment                                     ISO 4885
                                 Vocabulary




 5      EQUIPMENT AND PYROMETRY
        Thermal processing equipment and related pyrometric equipment shall be controlled in
        accordance with AMS 2750 (DIN/EN 3452).


        Heating Equipment
        Automatic temperature controllers and data recording instruments conforming to AMS
        2750 (DIN/EN 3452) are required on each furnace. Instrumentation, thermocouples, test
        equipment accuracy shall conform to AMS 2750 (DIN/EN 3452). Equipment which
        cannot be controlled and tested in accordance with AMS 2750 (DIN/EN 3452) shall be
        controlled and tested as directed by Metallurgy.

        Quenching Equipment
        Quench baths shall permit complete immersion of parts, shall have a temperature indicator
        with a sensor in the quench media, and shall be free from visible contamination, which
        could detrimentally affect the process. Tanks with oil should be equipped with a device
        forcing oil circulation for better heat exchange during quenching. Bath maintenance
        programs shall be established and when using polymers, a concentration control system
        shall be established.

        Quenching Media
        Except when marquenching, the temperature of the bath shall insure the proper cooling
        speed to produce a microstructure that will meet property requirements of the final part
        specification.




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 6   GENERAL HEAT-TREAT REQUIREMENTS
     Preheating
     Preheating between 900 to 1200 °F (482-649 °C) is recommended before heating parts
     above 1300 °F (704 °C) if the parts have been previously hardened to 35 Rc (345 VHN 10
     Kg) or greater, or if geometry of the part may produce excessive stresses during heat up.
     When preheating parts above 570 °F (300 °C), a protective atmosphere is recommended to
     reduce surface oxidation. Air, without a protective atmosphere, is acceptable when
     preheating parts below 570 °F (300 °C).

     Soaking
     Soaking shall commence when the control thermocouple reaches the specified set
     temperature.

     Tempering
     Tempering shall occur within 4 hours of quench. Soaking time shall not be less than 2
     hours plus one hour additional for each inch of thickness or fraction thereof greater than 1
     inch. Parts may be snap tempered for 2 hours at a temperature that is lower than the
     tempering temperature.

     Straightening
     For parts having a minimum tensile strength below 180 KSI (40 Rc) or 1241 MPa (392
     VHN), straightening may be accomplished without stress relieving. For parts having a
     minimum tensile strength of 180 KSI (1241 MPa) or above and straightened at room
     temperature, straightening shall be followed by stress relieving at a temperature not higher
     than 50 °F (28 °C) below the tempering temperature.

     Cleaning
     The heat-treat department should receive clean parts. Parts shall be cleaned prior to heat
     treatment only if it is necessary to remove contaminants that could have a deleterious effect
     on the surface visual appearance, surface microstructure, or part performance. Cleaning
     after heat treatment (quenching) should be performed as necessary to ensure the parts meet
     cleanliness requirements.

     Masking
     Coatings or plating used for the protection of surfaces during heat treatment shall be
     approved by Metallurgy. The type of masking used shall be reviewed to ensure that the
     furnace atmosphere is not contaminated by its use.

     Spacing/Racking
     Parts shall be racked and supported primarily to ensure access of the heating atmosphere
     and quenching media to all surfaces of all parts and secondarily to minimize distortion.




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 7   THROUGH-HARDENING
     Quenching and Tempering
     Quenching and tempering shall be in accordance with ASTM 2759/1 and ASTM 2759/2.
     The heating atmosphere shall be neutral to the surface of the steel being treated to prevent
     decarburization or carburization of the steel surface.

     Decarburization
     For parts heat treated to 220 KSI (46 Rc) or 1517 MPa (458 VHN) and above, the depth of
     decarburization (complete decarb is not permitted) after all heat-treat operations shall not
     exceed 0.003 inches (0.08 mm) on any surface. For parts heat treated to less than 220 KSI
     (46 Rc) or 1517 MPa (458 VHN), the depth of partial decarburization (complete
     decarburization not permitted) after all heat-treat operations, shall not exceed 0.005 inches
     (0. 13 mm).
     The depth of decarburization shall be determined by making a microhardness traverse per
     ASTM E384 (DIN 50190 1-3), using at least 250X magnification and recording hardness
     versus depth below the surface. The boundary of decarburization shall be the point at
     which the Knoop or equivalent hardness is 20 points (approximately 18 VHN points) less
     than the base hardness.

     Carburization or nitriding
     In through-hardened parts, furnace atmospheres which increase the Carbon content of
     surfaces above the maximum for the respective composition and/or increase the surface
     hardness 20 points Knoop or equivalent (approximately 18 VHN points) above the core
     hardness, are not acceptable. In addition, the microstructure shall not show any evidence
     of carburization or nitriding.

     Intergranular attack
     Intergranular oxidation, as determined by metallographically etching specimens, shall not
     exceed .0005 inches (0.013 mm) on parts heat treated to 220 KSI (46 Rc) or 1517 MPa (458
     VHN) and above, and .0007 inches (0.018 mm) on parts heat treated to less than 220 KSI
     (46 Rc) or 1517 MPa (458 MPa).

     Core hardness
     Core hardness shall be determined in the most massive or functional section of the part
     unless specified otherwise.


 8   GAS CARBURIZING
     Gas carburizing shall be in accordance with AMS 2759/7 (DIN 17022-3).

     Case Carbon Content
     Surface carbon of finished heat treated parts shall be 0.70 to 1.00%. The surface carbon
     content of parts in process may exceed 1.00% when boost and diffuse processes are being
     utilized, such as with vacuum and plasma carburizing.



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     Case Microstructure
     Retained austenite shall not exceed 15% unless specified otherwise on the engineering print
     or heat-treat process instructions. Retained austenite shall be determined by visual
     comparison (See Appendix D: Martensite/Austenite Chart) unless x-ray diffraction is
     required by the engineering print or heat-treat process instructions. When x-ray diffraction
     is required, the method used shall be agreed upon between the heat-treater and the
     customer. Intergranular (grain boundary) carbides shall be scattered and discontinuous and
     shall not be evident in more than (30%) of the grain boundaries (See Photograph 5.2 in
     SEP 1520). Case microstructure shall be predominantly tempered martensite.
     Intergranular oxidation shall not exceed 0.0005 inches (0.013 mm) in depth from the
     unmachined surfaces.

     Case Hardness
     Case hardness shall be 58-62 Rc (653-746 VHN) and shall be determined in accordance
     with ASTM E18 (EN 6508 -1,2,3) on the carburized and hardened surface of the finished
     part using a superficial hardness test appropriate for the depth of case specified (See
     Appendix B).

     Case Depth (effective case depth) – see section 20 for detailed instructions
     Effective case depth is defined as the depth below the surface of the part where the
     hardness is equal to or greater than 50Rc (513 VHN) as measured by a microhardness
     survey in accordance with ASTM E384 or DIN 50190. Note that DIN 50190 limiting
     hardness (LH) is 550 VHN (52.5 Rc) - See Appendix C. Effective case depth shall be
     determined by optical method measurement on a metallographically polished and etched
     (4% nital) sample when the core hardness exceeds 45 Rc (446 VHN). In applying the
     optical method, the effective case depth shall be defined as the depth of the midpoint of
     the microstructural transition zone laying between the higher carbon outer surface and the
     low carbon core.

     Total Case Depth
     Total case depth is the depth from the surface to the point where core microstructure
     characteristics and case structure characteristics can no longer be differentiated. This point
     can be determined by hardness gradient, microstructure changes, or carbon concentration
     gradient.

     Quenching
     Parts may be direct quenched (cooled to austenitizing temperature prior to quenching)
     rather than being slow cooled to room temperature and rehardened.

     Selective Carburizing
     Selective carburizing may be accomplished by masking. Unless specified otherwise,
     threaded ends of shafts shall be masked prior to carburizing.

     For Gears and Splines
     For gears and splines, the case depth applies to the teeth surfaces at the pitch diameter.
     Case depth at the root of the gear teeth and root of the spline teeth shall not be less than
     75% of the minimum specified case depth. Surface hardness of gear and spline teeth roots

GS-0062.A                                                                                Page 9 of 22
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     may be 1 point Rc (approximately 20 VHN points) lower than that specified at the pitch
     diameter.


 9   GAS NITRIDING
     Gas nitriding shall be in accordance with AMS 2759/6 (DIN 17022-4).

     Equipment
     Equipment shall be available for introducing ammonia into the furnace at a controlled rate.
     A separate system for ammonia dissociation is recommended. Where ammonia
     dissociation is used, the equipment shall be capable of maintaining the atmosphere within
     +/- 5% of the selected percent dissociation.

     Decarburization/Contamination
     Surfaces to be nitrided shall be free from decarburization and contaminants such as grease,
     oil, and scale, which could interfere with nitrogen diffusion.

     Stress Relieving
     Unless otherwise specified, parts which have been ground or otherwise mechanically
     worked after hardening, shall be stress relieved prior to nitriding. The stress relieving
     temperature shall not be greater than 50°F (28 °C) below the tempering temperature
     (where applicable).

     Nitriding Temperature
     Unless specified otherwise, the nitriding temperature range shall be 940-1050 °F (504-566
     °C) and should not be greater than 50°F (28 °C) below the tempering temperature.

     Microstructure
     The microstructure shall exhibit a uniform distribution of nitrides diminishing gradually
     from the surface to the core. There shall be no evidence of a continuous nitride network in
     grain boundaries. Unless otherwise specified, the maximum thickness of the compound
     zone (white layer) shall be 0.001 inches (25 m).

     Case Depth
     Unless otherwise specified, case depth requirements shall be interpreted as either total case
     depth (compound + diffusion zone) or depth of the compound zone only. Total case
     depth is the depth of the continuous etching subsurface zone, determined
     metallographically on the as-nitrided part using 4% nital etching solution. On those
     materials that do not respond to etching, the total case depth is the depth below the surface
     at which microhardness is 50 HVN higher than that of the core, as determined by a Knoop
     or Vickers hardness traverse, in accordance with ASTM E 384.
     Effective case depth, where specified, shall be in accordance with drawing requirements
     and is the depth to which a specified hardness in accordance with ASTM E 384 or DIN
     50190-2 is attained. Case depth defined by DIN 50190-2 is core hardness + 50HV0.5 (See
     Appendix C).


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     Surface Hardness
     Surface hardness shall be determined by Rockwell superficial hardness or microhardness in
     accordance with ASTM E 18, ASTM E 92, or ASTM E 384 (EN 6056 -1,2,3 or DIN
     50190 -1,2,3). See Appendix B for description of thickness limits versus hardness method
     and test load. Compound zone hardness may be verified with the use of hardened files
     calibrated in increments of 5 points Rc (approximately 100 VHN).

     Surface Finish Effect
     The capability of a surface to accept a nitride case is influenced by its surface finish.
     Burnished, polished, and work hardened surfaces in general will not nitride satisfactorily.
     Abrasive blasting of all surfaces is recommended prior to nitriding.


 10 CARBONITRIDING
     Microstructure
     Case microstructure shall be in accordance with the requirements of gas carburizing in
     section 8. Additionally, excessive nitride needles shall not be present when examined at a
     magnification of 500X.

     Case Depth and Hardness
     Definition and determination of carbonitrided case depth and hardness shall be in
     accordance with the methods used for gas carburizing in section 8.


 11 GASEOUS NITROCARBURIZING
     Gaseous nitrocarburizing shall be in accordance with AMS 2757 (DIN 17022-4) and shall
     consist of a continuous thin epsilon-iron-carbonitride compound layer. Basically, the
     nitrocarburizing process is a thermochemical treatment carried out in a gaseous media,
     which involves diffusional additions of both nitrogen and carbon to the surface of ferrous
     materials at temperatures within the stress relief range. The primary objective is to provide
     an improved wear and fatigue resistant surface to carbon steel, alloy steel, and cast iron
     parts. Because the tempering is carried out at temperatures below 1200°F (649°C),
     retention of core properties and good dimensional control are achieved. An ad ditional
     benefit of improved corrosion resistance, through the formation of a continuous
     compound layer on the surface, can eliminate the need for protective plating.

     Hardening
     Parts where core hardening is specified shall be tempered at a temperature not less than
     50 °F (28 °C) above the nitrocarburizing temperature.

     Stress Relieving
     Parts which have been machined or straightened prior to nitrocarburizing, may be stress
     relieved at a temperature not less than 40 °F (20 °C) above the nitrocarburizing
     temperature.




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     Quenching
     A range of properties can be obtained by controlling the rate of cooling from the treatment
     temperature. Parts may be quenched in oil, water, soluble oil solutions, aqueous polymer
     solutions, inert or nitrocarburizing atmospheres, or air.

     Depth of Compound Layer
     The depth of compound layer shall be determined in accordance with the procedure of
     SAE J423 (DIN 50190 -1,2,3) or ARP 1820 microscopic methods, at not less than 500X
     magnification. Typical compound depth range for carbon steel, low alloy steel, and cast
     iron is 0.00015 inch (0.00038 mm) to 0.0010 inch (0.025 mm).

     Presence of Compound Layer
     The presence of a compound layer shall be confirmed by means of a chemical spot test. A
     drop of copper ammonium chloride (see section 18, note 1) or copper sulfate solution (see
     section 18, note 2) applied to a clean nitrocarburized surface of a part shall turn a reddish
     brown color after 15 seconds. If copper plates out on the surface, the compound layer is
     not present.

     Compound Layer Hardness
     The layer hardness shall be the equivalent of 60 Rc (697 HV10) or greater determined in
     accordance with SAE J864 for file hardness. Microhardness testing of the surface may be
     done in accordance with engineering print and /or specification requirements.

     Diffusion Zone Hardness
     Diffusion zone hardness when required by specification and/or engineering print shall be
     determined by microhardness measurements in accordance with ASTM E384 (DIN 50190-
     2) or by the chordal method of ARP 1820.

     Diffusion Zone Depth
     Diffusion zone depth, when required by specification and/or engineering print, shall be
     determined in accordance with ASTM E384 (DIN 50190-2) and is defined as the depth at
     which the hardness gradient exceeds the core hardness by 50 HV 0.5Kg (approximately 5
     Rc). See Appendix C.

     Compound Layer Structure
     The compound layer microstructure, when viewed at 500X in a representative field in the
     upper half of the compound zone, shall not contain a level of porosity and oxides greater
     than the amount stated in the specification. The compound layer at the substrate interface
     shall not exhibit residual porosity and oxides exceeding 5% for steel and 15% for cast iron.
     Although it is expected that the compound layer will consist primarily of epsilon iron
     nitride, the specific mix of epsilon and gamma prime may be specified by specification
     and/or engineering print.




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 12 SALT BATH NITROCARBURIZING
     There are several versions of salt bath nitrocarburizing that are capable of providing similar
     compound and diffusion layers with similar properties to that achieved by the gaseous
     process. A few of these industrial processes are: Tennifer QPQ and Melonite QPQ. The
     requirements listed under gaseous nitrocarburizing in section 11 apply to relevant salt bath
     nitrocarburizing process quality demands. Salt bath nitrocarburizing temperatures must be
     greater than gas nitrocarburizing temperatures, which are typically 570-590°C (1058-
     1094°F).


 13 INDUCTION HARDENING
     Induction hardening is a process in which high frequency electromagnetic radiation is
     coupled to the steel part, producing induced currents that cause the heating in the steel.
     Heating of the steel does not occur just on the surface, but also in the surface layers. The
     depth of heating is related inversely to the frequency, in that higher frequency produces
     heating to a shallower depth.
     The primary objective of induction heating is to provide an improved wear and fatigue
     resistant surface for carbon steel, alloy steel, and cast iron parts. This is accomplished by
     heating above the AC3 and quenching to produce a hardened surface and an accompanying
     residual compressive surface layer.
     The equipment used to heat-treat a component shall be fully capable of processing the part
     with adequate controls on power levels, heat times, quench times, quench temperature, and
     other key processing parameters.

     Key Parameters and Controls
     The key parameters of an induction hardening process are: machine setting, frequency,
     energy, cooling, tool setting, temperature and concentration of quench media. The heat-
     treater should have a documented plan for controlling each of these parameters.

     Surface Hardness
     The surface hardness specified on the engineering print shall be measured directly on the
     part surface in accordance with ASTM E18 (EN 6508 – 1,2,3), using the appropriate
     hardness scale compatible with the induction hardened depth. See Appendix B for
     description of thickness limits versus hardness method and test load. Surface hardness
     may also be measured on a sectioned sample at .003 inches (0.075 mm) per ASTM E384
     (DIN 50190-3).

     Depth of Hardening
     The case depth specified on the engineering print or heat-treat specification will normally
     be described in terms of the depth at which a minimum hardness is attained in accordance
     with microhardness testing per ASTM E384 (DIN 50190-3). Effective case is defined as
     the depth at which the hardness is 10 points Rc (approximately 120 VHN) less than the
     required minimum surface hardness (or 80% of the required minimum surface hardness as
     per DIN 50190-3) - See Appendix C. For example, for high carbon steel with a minimum
     surface hardness requirement of 60 Rc (697 VHN), 50 Rc (513 VHN) defines the effective
     case depth. For medium carbon steels with a minimum surface hardness requirement of 50

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     Rc (513 VHN), 40 Rc (392 VHN) defines the effective case depth. Total case depth, if
     required, is the depth at which core microstructure characteristics and case microstructure
     characteristics can no longer be differentiated. Total case depth may also be defined as the
     depth at which the hardness gradient exceeds the core hardness by 50 HV0.5Kg
     (approximately 5 Rc).

     Induction Hardening Pattern
     The area to be selectively induction hardened shall be defined on the engineering print or
     heat-treat specification. Unless specified otherwise, induction hardened surfaces may be
     bordered by a transition zone of up to 0.500 inches (12.70 mm) maximum. This transition
     zone is a region beyond the intended process zone and is characterized by hardness values
     less than those of the unheated base metal. Note that this transition (Heat Affect Zone -
     see definition of Heat Affect Zone - HAZ, in section 18, note 5) may contain residual
     tensile stresses that can potentially impact fatigue life of the component, so that the
     location of this zone can be extremely critical to the expected life of the component. It is
     recommended for good design practice that the HAZ should not exceed ½ the distance
     from the surface to the midpoint of the section being hardened.

     Microstructure after Induction Hardening
     Microstructural examination performed at 500X in the effective case depth region of the
     induction hardened and quenched and tempered part shall show a uniformly tempered
     martensitic microstructure. There shall be no evidence of over or under heating as
     revealed by incipient melting, retained austenite in excess of 15% (unless specified
     otherwise on the part drawing) and/or free ferrite.

     Microstructure prior to Induction Hardening
     It is recommended that the microstructure of carbon steel, alloy steel, and cast iron
     contains a minimum of 80% pearlite (predominantly lamellar or globular, mixed not
     acceptable) or 90% martensite prior to induction hardening to insure a rapid and uniform
     heat-treat response.

     Area Selected for Examination
     The area selected for examination of the pattern should represent the full pattern area.
     Examination with respect to surface hardness, depth of hardening, and microstructure
     should be located in the center of the pattern, unless specified otherwise. First-piece
     inspection is required in an induction hardening process. The heat-treater should have the
     capability of inspecting for cracks.

     Tempering
     Parts shall be tempered at a minimum temperature of 351 °F (177 °C). Although not the
     preferred method, induction tempering is allowed provided a suitable method has been
     demonstrated to achieve the print hardness requirement. Timing between induction
     hardening and tempering is critical, but it can vary by application. The time should be
     controlled to avoid cracking.




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 14 HYDROGEN EMBRITTLEMENT RELIEF BAKING
     Hydrogen relief baking of steel parts shall be in accordance with AMS 2759/9. Relief
     baking is performed to remove hydrogen infused during plating and other chemical
     processes such as stripping, chemical milling, pickling, de-burring, and etching. This relief
     baking is the responsibility of the facility performing the surface treatment.

     Parts to be Baked
     Hydrogen relief baking is applicable to parts made from carbon, low-alloy steel, and
     martensitic stainless steel (including precipitation hardened stainless) heat treated to a
     minimum strength of 180 KSI (1241 MPa) or heat treated to a minimum hardness of 40 Rc
     (392 VHN) or equivalent. It is also applicable to threaded fasteners heat treated to a
     minimum strength of 150 KSI (1034 MPa) or 34 Rc (336 VHN) or equivalent hardness,
     and steel parts which have been surfaced hardened (carburized, nitrided, carbonitrided,
     nitrocarburized, or induction hardened). Supplier should be aware that parts with a
     minimum strength even as low as 117 KSI (800 MPa) or minimum hardness of 22 Rc (250
     VHN) may be susceptible to hydrogen embrittlement and should take proper precautions.

     Baking Requirements
     Parts shall be baked after completion of each plating or other chemical process in
     accordance with the requirements of Table 1 of AMS 2759/9. Baking is not required
     between steps in a multiple step (plating/chemical process) sequence if interruptions do
     not exceed 2 hours, baking is started within 4 hours after the final step, and total time
     between start of first step and start of baking does not exceed 24 hours. When baking is
     required between steps, the minimum soaking time may be reduced to 3 hours for parts
     240 KSI (1655 MPa) or a minimum of 49 Rc (498 VHN) or equivalent. For higher
     strength parts the soaking time shall be a minimum of 6 hours. Nickel plated parts are an
     exception and shall be soaked for the required times of Table 1 of AMS 2759/9 for parts
     heat treated to a minimum strength of 200 KSI (1379 MPa).

     Baking Procedure
     The elapsed time between completion of plating or other chemical processing and baking
     shall not exceed 4 hours.
     The standard baking temperature is 375 °F (191 °C). The baking temperature for parts that
     are carburized or carbonitrided shall be 275 °F (135 °C). The baking temperature for parts
     made from 52100 and 440C that have been heat treated to a minimum strength of 220 KSI
     (1517 MPa) or a minimum hardness of 46 Rc (458 VHN) shall be 300°F (149 °C). The
     baking temperature for parts made from music wire is 325 °F (163 °C).
     Minimum baking times shall conform to Table 1 of AMS 2759/9. Typical baking times are
     either 8 hours or 23 hours depending on material, how material is processed, and plating
     process or chemical treatment.


 15 HEAT-TREAT PERSONNEL QUALIFICATIONS
     All personnel performing heat treating and associated operations shall be trained and
     approved in accordance with ARP 1962 (see 4.5 Table for DIN equivalent).



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 16 TESTING REQUIREMENTS
     Testing Capabilities and Requirements
     Heat treating facilities shall have the testing equipment necessary to perform the tests to
     verify conformance to requirements. Those measurements that are performed infrequently
     may be sourced to an outside laboratory.

     Preproduction tests
     Prior to the first shipment of a new part number, a significant process or product change,
     or shipment of a previously existing part number to a new customer, the appropriate
     testing should be performed as per the design specification (and PPAP material test
     requirements) to verify the appropriate material and process to meet the application intent.

     Acceptance/Production (Series) Tests
     Acceptance/production tests shall be performed on each lot of parts (see section 19, note 3
     and 4 for definition of lot). Unless specified otherwise, the following are required
     acceptance/production tests for each of these processes (note that part or parts selected
     for examination shall be after all thermal processes have been completed):
     Through-Hardening:          Surface hardness; core hardness; surface microstructure.
     Gas Carburizing:            Case hardness; surface and case microstructure; case depth.
     Gas Nitriding:              Case hardness; case microstructure; case depth.
     Carbonitriding:             Case hardness; surface and case microstructure; case depth.
     Gaseous Nitrocarburizing:   Depth of compound layer; presence of compound layer;
                                 compound layer hardness.
     Salt Bath Nitrocarburizing: Depth of compound layer; presence of compound layer;
                                 compound layer hardness.
     Induction Hardening:        Surface hardness; depth of hardened layer; microstructure of
                                 hardened layer; induction hardened pattern.

     Periodic Tests
     Periodic tests shall be performed at a frequency selected by the heat-treater (as per control
     plan) unless frequency of testing is specified otherwise by the engineering print. Unless
     specified otherwise, the following are required periodic tests for each of these processes
     (Note that part or parts selected for examination shall be after all thermal processes have
     been completed):
     Through-Hardening:          Core microstructure.
     Gas Carburizing:            Core hardness; core microstructure.
     Gas Nitriding:              Core hardness; thickness of compound zone.
     Carbonitriding:             Core hardness; core microstructure.
     Gaseous Nitrocarburizing:   Compound layer microstructure; diffusion zone hardness;
                                 diffusion zone depth.
     Salt Bath Nitrocarburizing: Compound layer microstructure; diffusion zone hardness;
                                 diffusion zone depth.
     Induction Hardening:        Core hardness; core microstructure.




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 17 TEST REPORT REQUIREMENTS
     Reports shall show the results of tests made on parts to determine conformance to
     acceptance/production, periodic, or preproduction tests as applicable. Reports shall
     include the purchase order number, shop order number, part number, furnace(s) used, load
     number(s), thermal processing temperatures, times, and cooling cycles used, temperature
     and method of straightening, dates, and quantity of parts heat treated.


 18 GENERAL OPERATING SYSTEM REQUIREMENTS
     The heat-treat must establish and maintain a documented operating system according to
     ISO 9001. This requirement applies to the quality system, the process and the maintaining
     of the heat-treat equipment.

18.1 Quality System
     The heat-treat shop shall establish and maintain a documented quality system as a means of
     ensuring that the products conform to requirements. Specifically, the shop must have
     documented procedure(s) for:
     a)     Receiving inspection
     b)     Process inspection
     c)     Final inspection
     d)     Nonconformity review and Disposition
     e)     Corrective actions
     f)     Process Control (Control Plans and FMEAs)

18.2 Contract Review
     The supplier/customer shall establish and maintain procedures for contract review and for
     the coordination of these activities.
     a) Clear drawings: The heat-treater must review the drawing and ensure that it provides
        clear information on: hardness, case depth, place of measurement, measurement
        parameters, measurement load, material, masking, etc. This review includes ensuring
        the material specified will consistently meet the final specifications after the heat-treat
        process. If this information is not clear, the heat-treater must request this information
        from engineering.
     b) Clear heat-treat orders
     c) Documentation of heat-treat orders
     d) Good description of parts

18.3 Process Control
     The heat-treat shop shall identify and plan the production, which directly effect quality, and
     shall ensure that these processes are carried out under controlled conditions
     a) The recording of processes
     b) The following of safety regulations
     c) The documenting of processes and process steps: As per Sauer-Danfoss PPAP
        requirement, the process parameters of the heat-treat process must be defined and a
        significant production run performed and tested to ensure compliance to the material
        specifications. Significant deviations from these process parameters are not allowed
        without signed deviation from the customer’s engineering function.

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18.4 Maintenance of the Heat-Treat Equipment
     The heat-treat shop shall establish and maintain a documented maintenance system as a
     means of ensuring that the technical equipment can consistently meet requirements.
     a)     Maintenance plans for the heat-treat equipment
     b)     Maintenance plans for the gas, energy and water supply
     c)     Maintenance plans for the control equipment
     d)     The documentation of maintenance actions




 19 APPENDIX A: General Notes

     1. Copper ammonium chloride solution: Dissolve 100 grams cupric chloride
        (CuCl2.2H2 O) in distilled water to make one liter. Add ammonium hydroxide to form a
        copper ammonium chloride complex.


     2. Copper sulfate solution: Dissolve 40 grams of copper sulfate (CuSO4.5H2O) in 1000 ml
        of distilled water and 5 ml wetting agent (e.g. glycerine); pH shall be 3.5 to 4.1.


     3. A lot (other then for induction hardening – see note 4 below) shall be all parts of the
        same part number processed in the same furnace load. See also section 4.3.2 of AMS
        2759 (see Table 4.1 for DIN equivalent): a lot shall be all parts of the same design,
        fabricated from the same alloy, heat treated to the same property requirements in the
        same furnace(s) at the same time, and presented for processor’s inspection at the same
        time. In addition, for a continuous furnace, it shall be those parts heat treated as a
        continuous production run during an eight-hour shift. When testing parts after
        operations (e.g. stress relieving, baking, hot or warm straightening) that occur after the
        final step of the heat operation (e.g. tempering, aging), a lot, in addition to the above,
        shall consist of parts stress relieved, baked, hot or warm straightened, etc using the same
        equipment at the same time.


     4. A lot for induction hardened parts shall be defined as all parts of the same part number,
        material, and condition processed together or sequentially within an 8 hour period, using
        the same equipment under identical control settings for heating and cooling, including
        the timing thereof.


     5. Heat Affected Zone (HAZ): The heat affected zone is the depth below the hardened
        surface which last exhibits microstructural evidence of having exceeded the lower
        critical temperature (Ac1) and/or that portion of the base metal within which
        microstructural and physical properties were altered by the treatment.




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20       APPENDIX B:
         Thickness Limits for Surface Hardness Measurements of Surface Treated Materials


         Thickness limits for surface hardness measurement of surface treated materials as a
         function of hardness method and test load are shown in Tables 1 and 2. The source for
         these tables is DIN 6773. A similar presentation of thickness limits is provided in ASTM
         E18 (not shown). ASTM E18 also provides correction factors for convex cylindrical
         surfaces.


                                                   Table 1
Thickness Limits for Surface Hardness Measurement Using Vickers
(Basis is DIN 6773)
                               Minimum Surface Hardness and Vickers Test Load

     Min. Case    200-300      >300-400      >400-500      >500-600    >600-700   >700-800     >800 (HV)
       Depth,      (HV)          (HV)          (HV)          (HV)        (HV)       (HV)
      Rht,Eht,
     Nht, (mm)*
        0,05         -            -             -            HV 0,5     HV 0,5    HV 0,5         HV 0,5
        0,07         -          HV 0,5        HV 0,5         HV 0,5     HV 0,5     HV 1           HV 1
        0,08       HV 0,5       HV 0,5        HV 0,5         HV 0,5      HV 1      HV 1           HV 1
        0,09       HV 0,5       HV 0,5        HV 0,5          HV 1       HV 1      HV 1           HV 1
         0,1       HV 0,5        HV 1          HV 1           HV 1       HV 1      HV 1           HV 3
        0,15        HV 1         HV 1          HV 3           HV 3       HV 3      HV 3           HV 5
         0,2        HV 1         HV 3          HV 5           HV 5       HV 5      HV 5           HV 5
        0,25        HV 3         HV 5          HV 5           HV 5      HV 10     HV 10          HV 10
         0,3        HV 3         HV 5         HV 10          HV 10      HV 10     HV 10          HV 10
         0,4        HV 5        HV 10         HV 10          HV 10      HV 10     HV 30          HV 30
        0,45        HV 5        HV 10         HV 10          HV 10      HV 30     HV 30          HV 30
         0,5       HV 10        HV 10         HV 10          HV 30      HV 30     HV 30          HV 30
        0,55       HV 10        HV 10         HV 30          HV 30      HV 30     HV 50          HV 50
         0,6       HV 10        HV 10         HV 30          HV 30      HV 50     HV 50          HV 50
        0,65       HV 10        HV 30         HV 30          HV 50      HV 50     HV 50          HV 50
         0,7       HV 10        HV 30         HV 50          HV 50      HV 50     HV 50          HV 50
        0,75       HV 30        HV 30         HV 50          HV 50      HV 50     HV 100         HV 100
         0,8       HV 30        HV 30         HV 50          HV 50      HV 100    HV 100         HV 100
         0,9       HV 30        HV 30         HV 50          HV 100     HV 100    HV 100         HV 100
         1,0       HV 30        HV 50         HV 100         HV 100     HV 100    HV 100         HV 100




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                                                                      Table 2
        Thickness Limits for Surface Hardness Measurement Using Rockwell and Rockwell Superficial (Basis is DIN 6773)

                Minimum Surface Hardness for Rockwell and Rockwell Superficial Test Loads

  Min.        82-85       >85-88       >88         60-68      >68-73     >73-78     >78      >44-54    >54-61    >61-67     >67
  Case      (HR 15N)     (HR15N)     (HR15N)     (HR30N)     (HR30N)    (HR30N)   (HR30N)   (HR45N    (HR45N    (HR45N    (HR45N)
 Depth,
Rht, Eht,
 (mm)*)
    0,1        -           -        HR15N          -            -          -         -         -         -         -          -
   0,15        -        HR15N       HR15N          -            -          -         -         -         -         -          -
    0,2      HR15N      HR15N       HR15N          -            -          -      HR30N        -         -         -          -
   0,25     HR15N       HR15N       HR15N          -            -       HR30N     HR30N        -         -         -          -
   0,35     HR15N       HR15N       HR15N          -         HR30N      HR30N     HR30N        -         -         -      HR45N
    0,4     HR15N       HR15N       HR15N        HR30N       HR30N      HR30N     HR30N        -         -      HR45N     HR45N
    0,5     HR15N       HR15N       HR15N       HR30N        HR30N      HR30N     HR30N        -      HR45N     HR45N     HR45N
  >0,55     HR15N       HR15N       HR15N       HR30N        HR30N      HR30N     HR30N      HR45N    HR45N     HR45N     HR45N



  Min.         70-75      >75-78      >78-81       >81        40-49      >49-55    >55-60     >60
  Case        (HR A)      (HRA)       (HRA)       (HRA)       (HRC)      (HRC)     (HRc)     (HRC)
 Depth,
Rht, Eht,
 (mm)*)
   0,4            -           -           -     HRA             -          -         -         -
  0,45            -           -     HRA         HRA             -          -         -         -
   0,5            -     HRA         HRA         HRA             -          -         -         -
   0,6      HRA         HRA         HRA         HRA             -          -         -         -
   0,8      HRA         HRA         HRA         HRA             -          -         -      HRC
   0,9      HRA         HRA         HRA         HRA             -          -      HRC       HRC
   1,0      HRA         HRA         HRA         HRA             -       HRC       HRC       HRC
   1,2      HRA         HRA         HRA         HRA          HRC        HRC       HRC       HRC

        *) Rht = Case depth for inductive and flame hardening
           Eht = Case depth for carburizing and carbonitriding
            Nht = Case Depth for nitriding and nitrocarburizing




        GS-0062.A                                                                                                 Page 20 of 22
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 21 APPENDIX C:

     Case Depth Determination According to DIN 50190

     1. Diagram of hardness versus distance from the surface
        Hardness
        (H0,5/1)




        LH
                                                                              3Xd



        CH
                                                                                 3Xd


                   CD           Distance from the
                                border (mm)                            2,5 X d



     LH = Limiting hardness* or effective case depth)
     CH = Core hardness
     CD = Case depth (Carburizing, Nitriding and Induction Hardening)

     *) The limiting hardness is determined as followed:
     a) Carburizing and carbonitriding:        550HV1 or 52.5 Rc (unless designated otherwise)

     b) Nitriding and nitrocarburizing:        Core hardness + 50HV0.5

     c) Induction hardening:                   80% of the required minimum surface hardness
                                               using HV1 (unless designated otherwise)

     2. Making an acceptable sample
     The hardness layer to be examined must be positioned at a right angle to the surface of the
     sample unless an oblique section method is being used. The sample should be ground and
     polished to a surface flatness of 1μm.

     3. Setting the impressions
     The gap between the center of the impressions shall be a minimum of 3.0 times the
     diameter of the impression and no closer to the edge of the sample than 2.5 times the
     diameter. The impressions have to be sufficiently distributed so that the curve of case
     depth can be easily determined.

     4. Result of the investigation
     The point of intersection between the hardness curve and the limiting hardness (LH) is
     defined as the effective case depth.



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 22 APPENDIX D: Martensite/Austenite Rating Chart
     The rating chart shown below provides a visual estimation of per cent Retained Austenite.
     A microstructure sample is to be prepared by polishing, etching in 3.5% Nital, and viewed
     at 400X. Note that this is a rough visual estimation and a requirement for more precise
     measured amounts of Retained Austenite should be determined by x-ray diffraction.




     CHANGE HISTORY:



GS-0062.A                                                                           Page 22 of 22

				
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