1、 Manufacturing StandardsFord Motor Company198611 HARDENING AND TEMPERING W-HT2-8Engineering Standards & Printed copies are uncontrolled.Systems Engineering (ESSE) Page 1 of 51. SCOPE: This process standard outlines the method of hardening andtempering of ferrous parts.2. APPLICATION: This standard a
2、pplies to parts which are heated in afurnace with a protective atmosphere or in a neutral salt bath. Forcertain parts of relatively thick cross-section and with end uses whichmay permit some surface decarburization, an air atmosphere may bepermitted by the affected Ford SQA and Quality activity.3. R
3、EQUIREMENTS:Note: A control plan as referenced in this standard is defined in QualitySystem Standard Q-101, Appendix A.3.1 PROCESS: Austenitizing may be performed in a:- continuous or batch-type muffle or radiant-tube furnace or- salt bath or- fluidized bed (if approved by the affected Ford SQA or Q
4、uality Activityand documented in the control plan).Muffle or radiant tube furnace hardening is the preferred method. Thefacilities should be able to heat in the range of 815-950C (1500-1750F).There shall also be facilities for quenching (refer to paragraph 3.6) andtempering.3.2 LOADING: The loading
5、practice shall be as follows:- Components must be thoroughly cleaned of oils and die lubricants andrelated materials prior to introduction to the austenitizing andtempering furnaces.- For parts for which distortion must be minimized (such as certaingears and shafts) appropriate fixturing shall be em
6、ployed.- The parts shall be suitably loaded to assure that every part isadequately heated during austenitizing and is properly exposed to thequenchant. The rate of loading must be within the thermal and weightcapacity of the furnace.- With any continuous process there shall be adequate spacing betwe
7、enlots which require different austenitizing, quenching, or temperingtimes or temperatures to ensure that lot is processed as necessary toattain the specified metallurgical properties.Manufacturing StandardsFord Motor Company198611 HARDENING AND TEMPERING W-HT2-8Engineering Standards & Printed copie
8、s are uncontrolled.Systems Engineering (ESSE) Page 2 of 53.3 FURNACE ENVIRONMENT: Atmospheres suitable for neutral hardeningnormally consist of carrier gas (endothermic gas or nitrogen-base gas or anitrogen-methanol blend*) with additions of a hydrocarbon gas such as methane(CH4) or propane (C3H8).
9、A neutral furnace atmosphere carbon potential shall beutilized for the grade of steel involved. The gas atmosphere must be circulatedin the furnace chamber and be of sufficient volume to ensure a positivepressure in the furnace. For parts with adequate cross-sections and end usesfor which limited de
10、carburization and scaling are permitted, an air furnaceatmosphere is acceptable if approved by the Ford SQA or Quality activity(anddocumented in the control plan).* It is essential that nitrogen-methanol furnace atmospheres be blended sothat the mole ratio of the nitrogen to methanol is two to one i
11、n order thatCO2, dew point, or oxygen potential control is feasable. Consequently,such atmospheres are permitted only when authorized by the affected FordSQA or Quality activity and documented in the control plan.3.4 TEMPERATURE: The temperature shall be controlled within+/- 5C (+/- 10F) of the set
12、point, as evidenced by continuous-recording pyrometers.3.5 AUSTENITIZING TIME: The parts shall be held for such time to assure that theparts have been completely austenitized.NOTE: Certain alloy steels may require extra holding time to assure adequatecarbon dissolution in the austenite.3.6 QUENCHING
13、: The parts shall be at a temperature of at least 25C(45 F) above the upper critical temperature (Ac3) at the time of quench.Direct quenching is preferred, and delayed quenching that forms austenitedecomposition products which degrade the part is specifically prohibited.Quenching systems must have p
14、rovisions for maintaining both maximum and minimumtemperatures of the quenchant specified in the process. Forced agitation must beprovided in the quench system to assure uniformity of temperature and efficiencyof quenchNOTE: In any of the quenching methods, parts must be cooled to alow enough temper
15、ature prior to tempering so that no furtherdetrimental transformation of austenite to fresh martensite willoccur upon cooling the parts to room temperature following thetempering operation.The following quenches have proven satisfactory, depending on therequired surface and core hardness and the amo
16、unt of distortionwhich can be tolerated. Quenching media other than those hereindescribed are not permissible unless specifically authorized by theaffected Ford SQA or Quality activity and documented in the control plan.3.6.1 DIRECT OIL QUENCH: Quench directly into a suitable, well-agitated oilmaint
17、ained at a temperature of 45-80C(110-180F).Manufacturing StandardsFord Motor Company198611 HARDENING AND TEMPERING W-HT2-8Engineering Standards & Printed copies are uncontrolled.Systems Engineering (ESSE) Page 3 of 53.6.2 HOT OIL QUENCH: Quench directly into a suitable well-agitated oil maintained a
18、ttemperatures of 80-175C (180-350F). This process requires that, for best andmost economical results, the oil surface area be covered by a protectiveatmosphere. This protection will prolong the life of quenching medium bypreventing oxidation and subsequent sludging of the oil.3.6.3 MARQUENCHING: Que
19、nch directly into a suitable, well-agitated oil maintained atthe temperature of 190-260C (375-500F).The establishment of the actual marquenching temperature must be based on thechemical analysis of the steel being treated.MOLTEN SALT MARQUENCHING PRECAUTIONS: This method, when used in conjunctionwit
20、h an carbon-bearing atmosphere furnace, must not have a fully-enclosedquench. The parts leaving the furnace atmosphere must come in contact with airbefore being quenched in a marquenching salt. This exposure is necessary toremove excess carbonaceous material before entering the strongly oxidizingque
21、nching salt. Although this Standard deals only with neutral hardening it isfelt to be appropriate to highlight the following caution. It cannot be toostrongly emphasized that this method is not to be used for direct quenching fromliquid carbonitriding salts. Should this process be used with a liquid
22、carbonitriding operation, it is absolutely necessary that an intermediate hightemperature neutral salt bath be utilized to wash off the carbonitriding saltsbefore entering the marquenching (oxidizing) salt.3.6.4 WATER-SOLUBLE POLYMER QUENCHANTS: Polymer quenchants with appropriateagitation may be sa
23、tisfactory for certain applications. However, priorconcurrence is required from the affected Ford SQA or Quality activity anddocumented in the control plan. Exposure of the quench media to theaustenitizing furnace atmosphere must be avoided to prevent addition ofexcessive moisture to the furnace env
24、ironment. The concentration andtemperature ranges to be used will be dependent upon the type of the part beingheat treated and the nature of the specific type of synthetic quenchant.3.6.5 BRINE/CAUSTIC QUENCHANT: A brine or caustic quenchant with appropriateagitation may be satisfactory for certain
25、applications. However, priorconcurrence is required from the affected Ford SQA or Quality activity anddocumented in the control plan before it may be used on Ford parts. Exposure ofthe quench media to the austenitizing furnace atmosphere in the furnace must beavoided to prevent addition of excessive
26、 moisture to the furnace environment.Normal concentration level of the quenchant ranges from 4 to 10% (salt orcaustic as applicable) while the temperature ranges from 15-27C (60-80F).3.7 TEMPERING: After quenching, the parts must be tempered in arecirculated air-type furnace or liquid bath at 150-20
27、0C(300-400F)for one hour at heat or to the appropriate higher temperature toobtain the hardness specified on the engineering print. Wheredimensional stability of the part is critical, the thermal treatmentfor stabilization should be specified on the engineering print. Donot temper at 260-370 C(500-7
28、00 F) unless specified by the affectedFord SQA or Quality activity (and documented in the control plan) or onthe engineering print.Manufacturing StandardsFord Motor Company198611 HARDENING AND TEMPERING W-HT2-8Engineering Standards & Printed copies are uncontrolled.Systems Engineering (ESSE) Page 4
29、of 5Caution: The parts should be tempered as soon as possible after quenching with amaximum delay of one hour recommended. Carbon steels containing more than 0.40%carbon, alloy steels containing more than 0.35& carbon or parts with sharpcorners, holes, recesses, or abrupt changes in section thicknes
30、s may requiremore restrictive delay times or other restrictions practices to precludecracking.3.8 MICROSTRUCTURE: The microstructure of the part shall consist oftempered martensite. Intermediate transformation structures in thecore of parts with larger cross-sections may be acceptable uponconcurrenc
31、e of the affected Ford SQA or Quality activity and documentedin the control plan. The part shall be free from surface decarburizationunless and acceptance level is permitted by the affected Product Engineeringactivity.3.9 HARDNESS: Unless otherwise specified, the surface hardness shall bechecked on
32、the Rockwell “C“ scale. Core hardness, when important,will be specified on the part print.3.10 PROCESS CONTROL: Suppliers utilizing this process standard must beable, by means of their existing process practices and records, toshow evidence of control of the process as per Ford Quality SystemStandar
33、d Q-101. Users of this process are referred to Ford ManufacturingStandard W-HTX-1 (for parts with heat treat characteristics denoted asControl Item () characteristics or for parts with Engineering prints denotedas “Must conform to Q-101 Appendix E“ or “Must conform to Q-101 Appendix F“)to W-HTX-12 (for heat treated parts not covered by W-HTX-1) in which controlpractices are outlined.Manufacturing StandardsFord Motor Company198611 HARDENING AND TEMPERING W-HT2-8Engineering Standards & Printed copies are uncontrolled.Systems Engineering (ESSE) Page 5 of 5FIGURE 1TEMPERING AND HARDING
