阅读说明：本技术 一种解决高温轴承钢W9Cr4V2Mo严重混晶的工艺方法 (Process method for solving serious mixed crystal problem of high-temperature bearing steel W9Cr4V2Mo ) 是由 谭楚琦 湛杰 徐益民 李英楠 米城栋 王兆和 于兴福 于 2019-11-20 设计创作，主要内容包括：本发明涉及高温轴承钢严重混晶的工艺方法,尤其涉及一种解决高温轴承钢W9Cr4V2Mo严重混晶的工艺方法,其包括对W9Cr4V2Mo轴承套圈锻件产生严重混晶组织的原因分析和解决方法。针对锻件的混晶组织结构和粗细晶粒的分布状态,通过多项工艺试验和检验,总结提出了消除混晶组织的热处理工艺方法。本发明工艺热处理后的产品淬火后平均晶粒度达到8.5级(标准7级或更细),混晶现象消除。完全达到了W9Cr4V2Mo钢制轴承套圈锻件在技术质量方面的要求。(The invention relates to a process method for serious mixed crystal of high-temperature bearing steel, in particular to a process method for solving the serious mixed crystal of the high-temperature bearing steel W9Cr4V2Mo, which comprises a method for analyzing and solving the reason that a W9Cr4V2Mo bearing ring forge piece generates a serious mixed crystal structure. Aiming at the mixed crystal structure and the distribution state of coarse and fine grains of the forge piece, a heat treatment process method for eliminating the mixed crystal structure is summarized through a plurality of process tests and examinations. The average grain size of the product after the heat treatment of the process reaches 8.5 grade (standard grade 7 or finer) after quenching, and the phenomenon of mixed crystals is eliminated. Completely meets the requirements of the W9Cr4V2Mo steel bearing ring forgings on technical quality.)

1. A process method for solving the problem of serious mixed crystal of high-temperature bearing steel W9Cr4V2Mo is characterized by comprising the following steps: the method comprises the following specific steps:

a. preheating materials: preheating a W9Cr4V2Mo steel bearing ring forge piece with severe mixed crystals to 750 +/-10 ℃, and preserving heat for 2 hours;

b. high-temperature heating: heating the forge piece in the step a to 940 +/-10 ℃ at the speed of 150 ℃ per hour, and preserving heat for 2 hours;

c. isothermal spheroidizing heating: b, furnace-cooling the forge piece in the step b to 740 +/-10 ℃ at the speed of 50 ℃ per hour, and preserving heat for 6-7 hours;

d. spheroidizing: and c, heating the forged piece in the step c to 860 +/-10 ℃, preserving heat for 6-7 hours, cooling to 740 +/-10 ℃ at the speed of 50 ℃ per hour, preserving heat for 6-7 hours, cooling to 680 ℃ at the speed of 20 ℃ per hour, cooling to 550 ℃ and 500 ℃ in a furnace, and discharging for air cooling.

Technical Field

The invention relates to a process method for serious mixed crystal of high-temperature bearing steel, in particular to a process method for solving the serious mixed crystal of a W9Cr4V2Mo steel aviation bearing ring.

Background

The W9Cr4V2Mo steel is a main material for manufacturing high-temperature bearings, and the steel has certain high-temperature hardness, high-temperature wear resistance, high-temperature contact fatigue strength, high-temperature impact resistance and high-temperature dimensional stability, but in the production process, bearing ring forgings made of materials with a plurality of furnace numbers have serious mixed crystal tissues after forging, spheroidizing, annealing and quenching, and can only be treated according to waste products according to the product acceptance standard. Due to the existence of mixed crystal structure, the size stability and the service life of the bearing are seriously influenced, the service performance of the bearing is greatly influenced, and even the aviation operation safety is influenced in serious cases.

The analysis on the reasons of mixed crystals shows that (1) the raw materials have component segregation and the phenomenon of uneven distribution of alloy elements and carbides exists, and during quenching and heating, due to the pinning effect of the carbides on crystal grains, when the carbides are more and are positioned near a crystal boundary, the grains can be inhibited from growing, the crystal grains at the part with few carbides are easy to grow rapidly, and when the growth of part of the crystal grains is not inhibited, the crystal grains are easy to coarsen, and finally mixed crystals are formed. (2) The mixed crystal formed by insufficient forging ratio or improper cogging temperature control in the steel ingot cogging process also has mixed crystal tissues of different degrees after rolling due to tissue inheritance, and the forged piece of the blank with defects after forging and rolling also has mixed crystal tissues. Therefore, a process method for eliminating the mixed crystal structure is provided, and the principle is as follows: (1) after quenching, a high-temperature short-time heating spheroidizing annealing process is adopted, and the distribution of carbide and alloy elements of the material is further homogenized through diffusion by short-time high-temperature heating; (2) because the sizes of the crystal grains in the mixed crystal structure are not uniform, the large crystal grains swallow the small crystal grains, so that the abnormal and thick crystal grains are obtained, then the unmelted spots in the large crystal grains and the residual crystal boundaries of the phagocytized small crystal grains are re-nucleated through the slow cooling process, and finally the uniform structure is obtained through spheroidization, so that the tissue inheritance is blocked. And a plurality of heat treatment process schemes for solving the problem of the mixed crystal of the forged piece are formulated according to the analysis result, and then a heat treatment process method for solving the problem of the serious mixed crystal of the forged piece through high-temperature short-time heating spheroidizing annealing is finally provided through continuous tests and inspections. The quenching grain size of the product is small and uniform through inspection, the structure is uniform, the technical quality requirement of bearing design is met, the economic loss caused by waste of mixed crystal batch of the product is avoided, the dimensional stability of the bearing is improved, and the service life of the bearing is prolonged.

Disclosure of Invention

In order to solve the technical problems, the invention provides a process method for solving the serious mixed crystal problem of the high-temperature bearing steel W9Cr4V2Mo, which completely eliminates the mixed crystal phenomenon and obtains a uniform structure with fine crystal grains.

In order to achieve the purpose, the invention adopts the following technical scheme, and the specific steps are as follows:

a. preheating materials: preheating a W9Cr4V2Mo steel bearing ring forge piece with severe mixed crystals to 750 +/-10 ℃, and preserving heat for 2 hours;

b. high-temperature heating: heating the forge piece in the step a to 940 +/-10 ℃ at the speed of 150 ℃ per hour, and preserving heat for 2 hours;

c. isothermal spheroidizing heating: b, furnace-cooling the forge piece in the step b to 740 +/-10 ℃ at the speed of 50 ℃ per hour, and preserving heat for 6-7 hours;

d. spheroidizing: and c, heating the forged piece in the step c to 860 +/-10 ℃, preserving heat for 6-7 hours, cooling to 740 +/-10 ℃ at the speed of 50 ℃ per hour, preserving heat for 6-7 hours, cooling to 680 ℃ at the speed of 20 ℃ per hour, cooling to 550 ℃ and 500 ℃ in a furnace, and discharging for air cooling.

And (b) preserving heat at 940 +/-10 ℃ for 2 hours, blocking tissue inheritance by using the thermodynamics and kinetics principles, and improving the uniformity of each component by diffusion.

Step c furnace-cooling 940 deg.C to 740 + -10 deg.C at a rate of 50 deg.C per hour to obtain nucleation conditions.

Compared with the prior art, the invention has the advantages that:

the average grain size of the product after quenching reaches 8.5 grade (standard grade 7 or finer), and the mixed crystal phenomenon is eliminated. The method completely solves the product quality problem caused by mixed crystal of the bearing ring forge piece, meets the requirements of the product on the technical aspect and the use aspect, simultaneously improves the dimensional stability of the bearing, prolongs the service life of the bearing, and avoids economic loss caused by batch waste of the crystal grain size mixed crystal of the forge piece.

Drawings

FIG. 1 is a metallographic examination of a mixed crystal of the raw materials of the present invention;

FIG. 2 is a metallographic examination chart of mixed crystals of the bearing ring forging of the present invention

FIG. 3 is a graph of a high temperature short time spheroidizing annealing process of the present invention;

FIG. 4 is a metallographic examination diagram of a bearing ring forging after mixed crystals are eliminated.

Detailed Description

The invention is further described with reference to the accompanying drawings:

the method comprises the following specific steps:

a. preheating materials: preheating a W9Cr4V2Mo steel bearing ring forge piece with severe mixed crystals to 750 ℃, and preserving heat for 2 hours;

b. high-temperature heating: b, heating the forged piece in the step a to 940 ℃ at the speed of 150 ℃ per hour according to the thermodynamic principle and the kinetic principle, and preserving heat for 2 hours;

c. isothermal spheroidizing heating: b, furnace-cooling the forge piece in the step b to 740 ℃ at the speed of 50 ℃ per hour, and preserving heat for 6 hours to ensure that mass points obtain a re-nucleation condition;

d. spheroidizing: and c, heating the forged piece in the step c to 860 ℃, preserving heat for 6 hours, cooling to 740 ℃ at the speed of 50 ℃ per hour, preserving heat for 6 hours, cooling to 680 ℃ at the speed of 20 ℃ per hour, cooling to 550 ℃ in a furnace, discharging and air cooling.

Firstly, measuring the uniformity of the effective heating zone temperature of the heating equipment, determining the position, the effective area and the space of the effective heating zone of the heating furnace, and ensuring the heating quality of a blank;

secondly, engineering technicians participating in scientific research experiments do detailed analysis and research and a large number of process tests in the aspects of technology, process and product quality control.

By inspecting the forged piece after high-temperature short-time spheroidizing annealing treatment, the average grain size of the product after quenching reaches 8.5 grade (standard grade 7 or thinner), and the phenomenon of mixed crystal is eliminated. The method completely solves the product quality problem caused by mixed crystal, meets the requirements of the product on the technical aspect and the use aspect, improves the structure uniformity of the forging, improves the dimensional stability of the bearing, prolongs the service life of the bearing, and avoids economic loss caused by batch waste of the crystal grain size mixed crystal of the forging.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.