CN110527792B - Tempering method for reducing residual stress - Google Patents
Tempering method for reducing residual stress Download PDFInfo
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- CN110527792B CN110527792B CN201910792183.8A CN201910792183A CN110527792B CN 110527792 B CN110527792 B CN 110527792B CN 201910792183 A CN201910792183 A CN 201910792183A CN 110527792 B CN110527792 B CN 110527792B
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- 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
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- 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
- C21D11/00—Process control or regulation for heat treatments
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention discloses a tempering method for reducing residual stress, which comprises the steps of heating, heat preservation and cooling in sequence, wherein the heating comprises two stages, the first stage is a high-speed heating stage, materials or parts to be tempered are rapidly heated to a temperature T1 from room temperature, the larger the size of the materials or the parts is, the higher the temperature T1 is, the second stage is a low-speed heating stage, and the materials or the parts to be tempered are slowly heated to a set tempering temperature from the temperature T1 for heat preservation. The method enhances the regulating and controlling effect of tempering on the residual stress, inhibits the formation of new residual stress in the tempering process, and is beneficial to improving the obdurability of the material.
Description
Technical Field
The invention belongs to the field of heat treatment, and particularly relates to a tempering method for reducing residual stress.
Background
Quenching is a basic process method for improving the strength of a material in the preparation process of a metal material. However, quenching not only improves the strength, but also introduces a high level of residual stress into the material, which significantly reduces the fatigue life, stress corrosion resistance, and the like of the material, and also easily causes changes in the shape and size of the material or parts during processing and use.
Tempering is a process method in which the quenched metal material is heated to a temperature below the critical temperature Ac1 (the temperature at which austenite begins to form when the steel is heated) and is kept warm to reduce the stress level in the material and regulate the quenching residual stress. The regulation and control mechanism of the residual stress during tempering is as follows: by providing proper activation energy for the supersaturated solid solution, the precipitation, distribution and evolution of a precipitated phase are controlled, and the performance and residual stress distribution of the material are further regulated and controlled. Therefore, heat input is a key element influencing the regulation of precipitated phases, and in order to obtain a low residual stress level, the tempering temperature has to be increased and the tempering time has to be prolonged in actual production, which inevitably damages the key mechanical properties of the material.
In addition, during the tempering process, the residual stress of the material surface and the material core has different changing trends, the residual stress of the core is continuously reduced, and the residual stress of the surface shows a trend of being reduced first and then being increased. Resulting in a reduction of residual stresses in the material by only 60-70% after tempering. Moreover, the increase in residual stress on the surface of the material tends to cause the stress state on the surface of the material after the tempering treatment to be a tensile stress state, which reduces the fatigue life and stress corrosion resistance of the material or part, and may cause cracking of the part or material in a severe case. Therefore, the development of a reasonable tempering process is the key for fully reducing the internal quenching stress of the material and improving the service performance of the material.
Disclosure of Invention
The invention aims to provide a tempering method for reducing residual stress, which enhances the regulating and controlling effect of tempering on the residual stress, inhibits the formation of new residual stress in the tempering process and is beneficial to improving the obdurability of materials.
The technical scheme adopted by the invention is as follows:
a tempering method for reducing residual stress sequentially comprises the steps of heating, heat preservation and cooling, wherein the heating comprises two stages, the first stage is a high-speed heating stage, materials or parts to be tempered are rapidly heated to a temperature T1 from room temperature, the larger the size of the materials or the parts is, the higher the temperature T1 is, the second stage is a low-speed heating stage, and the materials or the parts to be tempered are slowly heated to a set tempering temperature from the temperature T1 for heat preservation.
Further, the temperature increase rate in the high-speed temperature increase stage is not limited to promote precipitation and dispersion distribution of the second phase.
Further, the temperature rise rate V in the low-speed temperature rise stageHeatingLimited, the following formula must be satisfied
In the formula, VHeatingThe temperature rise speed is the temperature rise speed in the tempering heating process in the low-speed temperature rise stage; a is an adjustment coefficient; k is the thermal conductivity of the material or the part; sigmasIs the yield strength of the material or part at the temperature T; α is a thermal expansion coefficient; rho is the density of the material or the part; c is the specific heat of the material or part; e is the modulus of elasticity of the material or zero at the temperature T.
Further, the method is applicable to metal materials including steel materials and aluminum alloy materials.
Further, the temperature T1 ranged from 300 ℃ to 500 ℃.
The invention has the beneficial effects that:
one of the main reasons for the limited ability of adjusting the residual stress during the tempering process and the formation of the tensile stress state on the surface after the tempering process is the temperature stress generated during the tempering temperature rise process, and the higher the tempering temperature rise rate is, the larger the temperature stress is, and from the temperature stress perspective: the temperature rise rate during tempering heating is reduced, so that the temperature difference between the surface of the material or the part and the core part can be reduced, and the influence of temperature stress on the tempering residual stress regulation effect is reduced. However, from the perspective of tissue regulation, there are three factors that determine the effect of residual stress regulation, namely: dislocation density inside the material, size of the precipitated phase, and volume percentage of the precipitated phase. Wherein the dislocation density directly affects the size, volume percentage and dispersion degree of the precipitated phase. Therefore, from the view of the evolution mechanism of the residual stress, the high temperature rise rate is beneficial to maintaining the dislocation density in the material and enhancing the regulation and control effect of the residual stress. The method adopts a step heating mode to carry out tempering heating, namely, the dislocation density and carbide distribution in the tissue are adjusted by utilizing a high heating rate, the regulation and control effect of tempering on the residual stress is enhanced, and the tempering new residual stress caused by the temperature stress is inhibited by virtue of a low heating rate.
Drawings
FIG. 1 is a flow chart of the present invention.
Detailed Description
The invention is further described below with reference to the figures and examples.
A tempering method for reducing residual stress is shown in figure 1, and comprises the following steps of heating, heat preservation and cooling in sequence, wherein the heating comprises two stages, the first stage is a high-speed heating stage, materials or parts to be tempered are rapidly heated from room temperature to a temperature T1, the temperature T1 ranges from 300 ℃ to 500 ℃, the larger the size of the materials or the parts is, the higher the temperature T1 is, the second stage is a low-speed heating stage, and the materials or the parts to be tempered are slowly heated from the temperature T1 to a set tempering temperature for heat preservation.
One of the main reasons for the limited ability of adjusting the residual stress during the tempering process and the formation of the tensile stress state on the surface after the tempering process is the temperature stress generated during the tempering temperature rise process, and the higher the tempering temperature rise rate is, the larger the temperature stress is, and from the temperature stress perspective: the temperature rise rate during tempering heating is reduced, so that the temperature difference between the surface of the material or the part and the core part can be reduced, and the influence of temperature stress on the tempering residual stress regulation effect is reduced. However, from the perspective of tissue regulation, there are three factors that determine the effect of residual stress regulation, namely: dislocation density inside the material, size of the precipitated phase, and volume percentage of the precipitated phase. Wherein the dislocation density directly affects the size, volume percentage and dispersion degree of the precipitated phase. Therefore, from the view of the evolution mechanism of the residual stress, the high temperature rise rate is beneficial to maintaining the dislocation density in the material and enhancing the regulation and control effect of the residual stress. The method adopts a step heating mode to carry out tempering heating, namely, the dislocation density and carbide distribution in the tissue are adjusted by utilizing a high heating rate, the regulation and control effect of tempering on the residual stress is enhanced, and the tempering new residual stress caused by the temperature stress is inhibited by virtue of a low heating rate.
In this embodiment, the temperature increase rate in the high-speed temperature increase stage is not limited to promote precipitation and dispersion distribution of the second phase.
In the present embodiment, the temperature raising rate V in the low-speed temperature raising stageHeatingLimited, the following formula must be satisfied
In the formula, VHeatingThe temperature rise speed (unit, K/s) of the tempering heating process in the low-speed temperature rise stage is shown; a is an adjustment coefficient; k is the thermal conductivity (unit, W/(mK)) of the material or the part; sigmasIs the yield strength (unit, MPa) of the material or part at the temperature T; α is the coefficient of thermal expansion (unit, 1/K); rho is the density (unit, kg/m) of the material or part3) (ii) a c is the specific heat (unit, J/(kgK)) of the material or part; e is the modulus of elasticity (in MPa) of the material or zero at the temperature T. The tempering method is suitable for steel materials, aluminum alloy materials or other metal materials.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (3)
1. A tempering method for reducing residual stress is characterized in that: heating, heat preservation and cooling are sequentially carried out, wherein the heating comprises two stages, the first stage is a high-speed heating stage, the material or the part to be tempered is rapidly heated to the temperature T1 from the room temperature, the temperature T1 is higher when the size of the material or the part is larger, and the second stage is a low-speed heating stage, and the material or the part to be tempered is slowly heated to the set tempering temperature from the temperature T1 for heat preservation;
temperature rise rate in low-speed temperature rise stage
Limited, the following formula must be satisfied
In the formula (I), the compound is shown in the specification,
the temperature rise speed is the temperature rise speed in the tempering heating process in the low-speed temperature rise stage;
to adjust the coefficient;
is the thermal conductivity of the material or part;
is the yield strength of the material or part at the temperature T;
is the coefficient of thermal expansion;
is the density of the material or part;
is the specific heat of the material or part;
is the material or the modulus of elasticity at temperature T;
the temperature T1 ranges from 300 ℃ to 500 ℃.
2. The method of tempering to reduce residual stress of claim 1, wherein: the temperature rise rate in the high-speed temperature rise stage is not limited to promote the precipitation and dispersion distribution of the second phase.
3. The method of tempering to reduce residual stress of claim 1, wherein: the method is suitable for metal materials including steel materials and aluminum alloy materials.
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| SU905298A1 (en) * | 1980-01-25 | 1982-02-15 | Ворошиловградский машиностроительный институт | Method for thermoplastic strengthening of parts |
| JPH11236615A (en) * | 1998-02-20 | 1999-08-31 | Kawasaki Heavy Ind Ltd | Production of high chromium cast iron casting for impact wear resistance |
| EP2171104B9 (en) * | 2007-07-19 | 2018-08-29 | Muhr und Bender KG | Method for annealing a strip of steel having a variable thickness in length direction |
| CN101698902B (en) * | 2009-11-11 | 2011-10-05 | 江苏共昌轧辊有限公司 | Quenching method for integral cast steel supporting roll |
| CN102994888A (en) * | 2012-11-27 | 2013-03-27 | 天津大学 | Novel high-chromium ferritic heat resistant steel and thermo-mechanical treatment process |
| CN103361560A (en) * | 2013-07-03 | 2013-10-23 | 首钢总公司 | Cold-rolled hot-molded steel plate and production method thereof |
| CN105755232A (en) * | 2014-12-13 | 2016-07-13 | 青岛勤德索具有限公司 | Heat treatment process of high-chromium cast iron |
| CN104946870A (en) * | 2015-07-02 | 2015-09-30 | 杭州汽轮动力集团有限公司 | Heat treatment method for strength of 28CrMoNiV steel capable of improving industrial steam turbine rotor forge piece |
| CN107177783B (en) * | 2017-07-21 | 2018-09-14 | 东北大学 | A kind of Ultra-fine Grained martensite ferrite dual phase steel and its production technology with the distribution of bimodal ferrite crystal grain |
| CN109536696A (en) * | 2018-12-10 | 2019-03-29 | 宜兴市永昌轧辊有限公司 | A kind of tempering process of New Type of Cold Roller |
| CN109593927B (en) * | 2019-02-18 | 2020-09-01 | 安徽工业大学 | Method for producing grain-oriented pure iron by adopting secondary annealing |
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