GB2046311A - Treatment of steel parts to increase their resistance to fatigue and other properties - Google Patents

Treatment of steel parts to increase their resistance to fatigue and other properties Download PDF

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Publication number
GB2046311A
GB2046311A GB7911975A GB7911975A GB2046311A GB 2046311 A GB2046311 A GB 2046311A GB 7911975 A GB7911975 A GB 7911975A GB 7911975 A GB7911975 A GB 7911975A GB 2046311 A GB2046311 A GB 2046311A
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GB
United Kingdom
Prior art keywords
steel parts
fatigue
resistance
properties
carbonizing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB7911975A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
HUTA STALOWA WOLAKOMBINAT PRZE
Original Assignee
HUTA STALOWA WOLAKOMBINAT PRZE
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by HUTA STALOWA WOLAKOMBINAT PRZE filed Critical HUTA STALOWA WOLAKOMBINAT PRZE
Priority to GB7911975A priority Critical patent/GB2046311A/en
Publication of GB2046311A publication Critical patent/GB2046311A/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C21D1/44—Methods of heating in heat-treatment baths
    • C21D1/48—Metal baths
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/06—Surface hardening
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
    • C21D1/20—Isothermal quenching, e.g. bainitic hardening
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/28—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for plain shafts
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/82—After-treatment
    • C23C22/83—Chemical after-treatment
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F17/00—Multi-step processes for surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by subclass C21D or C22F or class C25
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Heat Treatment Of Articles (AREA)
  • Gears, Cams (AREA)

Abstract

This invention relates to a method of chemical and thermal treatment of steel parts such as gear wheels, shafts and sleeves for increasing their resistance to fatigue and wear and their hardness. The method is characterised by the following successively applied steps: phosphatizing, carbonizing, hardening and tempering. Steel parts treated according to this method will not develop a surface layer of low hardness and soft bainite patches during the carbonizing step, together with oxide occlusions mainly present along the grain boundaries and having a reduced content of alloying elements when compared with the alloying elements content of the base metal.

Description

SPECIFICATION Treatment of steel parts to increase their resistance to fatigue and other properties This invention relates to a method of chemical and thermal treatment of steel parts, such as gearwheels, shafts and sleeves in order to increase their resistance to fatigue and wear and their hardness.
It has been known for a long time in the machine construction industry to use a chemical and thermal method for the treatment of steel parts in order to improve the method for the treatment of steel parts in order to improve the above mentioned properties by carbonizing, hardening and tempering.
As a result of accurate testing of strength properties and microscopic examination, especially of failed and broken parts, we have found that in the carbon-enriched surface layer soft areas occur having a bainite structure, as a result of which the hardness and other strength properties are not uniform throughout the whole surface layer, thus causing a reduced working life for the treated parts.
Moreover within the surface layer there are found oxide occlusions, mainly along the boundaries of the grains having a reduced content of alloying elements. In consequence the hardenability is not uniform and surface damage will more readily occur.
Thus the strength properties of the thus treated steel parts are not optimum for given steel grades; these should be capable of improvement and for some time past there has been considerable research with the object of overcoming these defects.
It is already known to remove this defective surface layer from casehardened, hardened and tempered steel parts by grinding or by other mechanical methods. British Patent Specification No. 1 29701 6 discloses a galvanic method for removal of the damage surface layer.
The known methods have been found not to remove all unwanted oxide occlusions and/or bainite structures present in the surface layer, and the residual oxide acts as corrosion nucleii which accelerate the wear of the parts. The removal of a thin surface layer, while it is now common, also decreases the alloying elements content although, in general, these are not wholly removed, since they extend relatively deeply.
The present invention provides an improved method of chemical and thermal treatment of steel parts which ensures the casehardened parts against such surface defects so that they do not occur during the carbonizing step.
Thus the method of chemical and thermal treatment of steel parts in order to increase the strength properties according to the present invention is characterised by the following steps, successively applied: phosphatizing, carbonizing, hardening and tempering.
During the phosphatizing step, it is recommended to produce on the surfaces of the parts a 5-20 jum thick coating of zinc phosphate. Carbonizing, hardening and tempering steps are then carried out in that order under conditions appropriate to the particular steelgrade and according to the desired strength and fatigue properties.
By means of the method according to the present invention, when compared with the known methods, there are achieved higher and more uniform values for the time and resistance to fatigue and wear and hardness together with reliable hardenability properties.
It was found that using the method according to the present invention during the carbonizing step a defective surface layer is not formed, and thus it is not necessary to remove this layer.
It was also found that the carbonizing, hardening and tempering steps carried out after the phosphatizing step proceed normally and that the phosphatizing step does not decelerate the subsequent carbonizing.
The invention will be more readily understood from the following description of an example thereof.
EXAMPLE Ready machined gear wheels of low alloy construction steel, containing substantially 0.2% C; 0.8% Mn; 0.3% Si; 0.6% Cr; 0.5% Ni; 0.2% Mo; 0.03% Al and other elements common in steels such as P, S and Cu, in commonly occurring quantities and the balance being Fe, were cleaned, degreased and phosphatized in a bath containing zinc and iron phosphates so as to generate a 9-12 ym thick zinc phosphate coating integral with the substrate metal. Subsequently, the gear wheels are carbonized in an endothermic gaseous atmosphere to a depth of 0.9 mm, hardened in an oil bath and tempered, also in an oil bath.
Results of microscopic structured examination and values of hardness measurements determined for gear wheels which have been treated according to the invention when compared with these properties for gear wheels which have been casehardened according to the conventional method are given in the appended table.
TABLE Object File- Micro- Micro- Carbonexamined Scratch hardness structure izing hardness depth Gear wheels Lacking In the surcarbonized, None in uniform- face layers 0.9 mm hardened and ity there are low tempered 460-550 HV local soft bainite patches Gear wheels In the with 9-12 ,zm Uniform surface thick zinc 740-780 HV layers phosphate Good there are 0.9 mm coating, car- only unibonized, formly hardened and areas of low-tempered tempered martensite

Claims (3)

1. A method for the chemical and thermal treatment of steel parts in order to increase their resistance to fatigue, wear and other properties, characterised in that the following steps are successively applied: phosphatizing, carbonizing, hardening and tempering.
2. A method as claimed in claim 1, further characterised in that the phosphatizing is used to produce on the steel parts a 5-20 ym thick coating of zinc phosphate.
3. A method as claimed in either of claims 1 and 2, for increasing the strength of casehardened steel parts, substantially as hereinbefore described with reference to the Example.
GB7911975A 1979-04-05 1979-04-05 Treatment of steel parts to increase their resistance to fatigue and other properties Withdrawn GB2046311A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB7911975A GB2046311A (en) 1979-04-05 1979-04-05 Treatment of steel parts to increase their resistance to fatigue and other properties

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB7911975A GB2046311A (en) 1979-04-05 1979-04-05 Treatment of steel parts to increase their resistance to fatigue and other properties

Publications (1)

Publication Number Publication Date
GB2046311A true GB2046311A (en) 1980-11-12

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB7911975A Withdrawn GB2046311A (en) 1979-04-05 1979-04-05 Treatment of steel parts to increase their resistance to fatigue and other properties

Country Status (1)

Country Link
GB (1) GB2046311A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108274205A (en) * 2018-04-11 2018-07-13 芜湖三六机械有限公司 A kind of production technology of high-strength abrasion-proof pressure roller

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108274205A (en) * 2018-04-11 2018-07-13 芜湖三六机械有限公司 A kind of production technology of high-strength abrasion-proof pressure roller

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)