CN108842043B

CN108842043B - High-speed steel processing method for obtaining composite grain structure

Info

Publication number: CN108842043B
Application number: CN201810788050.9A
Authority: CN
Inventors: 周雪峰; 李文滔; 方峰; 蒋建清; 朱小坤
Original assignee: Jiangsu Tiangong Tools Co Ltd; Southeast University
Current assignee: Jiangsu Tiangong tools and new materials Co., Ltd; Southeast University
Priority date: 2018-07-18
Filing date: 2018-07-18
Publication date: 2020-06-16
Anticipated expiration: 2038-07-18
Also published as: CN108842043A

Abstract

The invention discloses a high-speed steel processing method for obtaining a composite grain structure, which comprises the following steps: (1) controlling the strain amount to carry out cold machining on the high-speed steel wire rod; (2) controlling annealing of the cold-processed wire rod obtained in the step (1); (3) and (3) repeating the circulation steps (1) to (2). The high-speed steel processing method can obtain the high-speed steel wire rod with composite grain structure characteristics by controlling the cold deformation and annealing process parameters and the cycle number and regulating the grain size, can simultaneously play the reinforcing effect of fine grains and the work hardening effect of coarse grains, and improves the strong plasticity of the material.

Description

High-speed steel processing method for obtaining composite grain structure

Technical Field

The invention relates to a high-speed steel processing method, in particular to a high-speed steel processing method for obtaining a composite grain structure.

Background

The high-speed steel has the advantages of high hardness, high wear resistance, good red hardness and the like, is widely applied to manufacturing various efficient and precise processing tools such as milling cutters, gear shaping cutters, turning tools, twist drills, bimetal saw blades and the like, and is an important basic material in the modern high-end equipment manufacturing industry.

The high-speed steel tool is manufactured by adopting high-speed steel rods and wires, and the preparation process comprises the following steps: smelting → refining → casting → electroslag remelting → forging → rolling → cold drawing/cold rolling → rod/wire. Due to the components and the structural characteristics of the high-speed steel, the high-speed steel wire rod is very easy to generate structural defects such as large precipitated carbide particles, adhesion, fracture, coarsening of the structure and the like in the processing process, so that the processing performance and the service performance of the high-speed steel wire rod are deteriorated.

Annealing is an important heat treatment means for improving the plasticity of high-speed steel wire rods. The annealing process of high-speed steel is divided into various types according to different annealing purposes. And (3) adopting complete annealing (recrystallization annealing), heating to a temperature above the austenite transformation temperature to recombine crystal lattices, eliminating most of the crystal lattice defects and recovering the plasticity of the material. And intermediate annealing (recrystallization annealing) is adopted to ensure that the material is subjected to recovery recrystallization to form new equiaxed grains, so that the processing capacity of the material is improved. After annealing by recrystallization or recrystallization, an annealed structure with uniform ferrite grain size is obtained.

The composite grain structure means that a large number of fine-sized grains and coarse-sized grains are present at the same time. Research shows that compared with a uniform grain size structure, the composite grain structure can simultaneously improve the strong plasticity of the material: the small-size crystal grains have a fine-grain strengthening effect, the large-size crystal grains are beneficial to keeping the processing and hardening capacity of the material, and meanwhile, the non-uniform deformation characteristic of the composite crystal grain structure is utilized to generate a strain gradient, so that the material has high strength and good plasticity.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problem that the traditional recrystallization annealing process or recrystallization annealing process can only obtain an annealing structure with uniform grain size, the invention provides a high-speed steel processing method for obtaining a composite grain structure.

The technical scheme is as follows: the invention relates to a high-speed steel processing method for obtaining a composite grain structure, which comprises the following steps:

(1) controlling the strain amount to carry out cold machining on the high-speed steel wire rod;

(2) controlling annealing of the cold-processed wire rod obtained in the step (1);

(3) and (3) repeating the circulation steps (1) to (2).

Preferably, in the step (1), the strain of the high-speed steel wire rod is controlled to be 0.1-0.3; too small amount of strain will not cause recrystallization, and too large amount of strain will cause uniform recrystallization.

Further, in the step (2), the annealing temperature is controlled to be 700-760 ℃, and the annealing time is controlled to be 2-20 min. The annealing temperature is too low, recrystallization does not occur, and the annealing temperature is too high, uniform recrystallization occurs.

Furthermore, in the step (3), the cycle number is not less than 3. Single cold deformation and annealing, uneven recrystallization is not obvious, and repeated circulation can amplify the effect of uneven recrystallization to obtain a composite grain structure. The number of repeated cycles is mainly determined by the cold deformation and the annealing process control, i.e. within the allowable range, the larger the deformation or the higher the annealing temperature, the larger the driving force for non-uniform recrystallization, and the cycle number can be reduced.

The invention principle is as follows: the processing method of the invention refines partial grains by utilizing uneven recrystallization so as to obtain a composite grain structure, and particularly, the invention controls the cold processing strain, annealing process and cycle number so as to cause the inside of the structure to generate uneven deformation and the new grains to generate uneven nucleation and growth so as to form the composite grain structure simultaneously having fine equiaxed grains and coarse equiaxed grains.

Has the advantages that: compared with the traditional recrystallization annealing process or recrystallization annealing process which can only obtain equiaxial grains with uniform size, the high-speed steel processing method can obtain the high-speed steel wire with composite grain structure characteristics by controlling the cold deformation, the annealing process parameters and the cycle number to regulate and control the grain size, and simultaneously plays a role in strengthening fine grains and processing and hardening coarse grains to improve the strong plasticity of the material.

Drawings

FIG. 1 is a scanning electron micrograph of M42 steel after processing according to example 1;

FIG. 2 is a scanning electron micrograph of M42 steel after processing according to example 2;

FIG. 3 is a scanning electron micrograph of M42 steel after processing according to example 3;

FIG. 4 is a scanning electron micrograph of M42 steel after processing according to example 4;

FIG. 5 is a scanning electron micrograph of M42 steel after treatment with a prior art recrystallization annealing process;

FIG. 6 is a scanning electron micrograph of M42 steel after treatment with a prior art recrystallization annealing process;

FIG. 7 is a scanning electron micrograph of M42 steel after a single cold deformation + annealing treatment in example 1;

FIG. 8 is a SEM image of M42 steel after two cold-deformation and annealing treatments in example 1.

Detailed Description

The technical scheme of the invention is further explained by combining the attached drawings.

Example 1

(1) Carrying out cold working deformation on the M42 high-speed steel wire rod, wherein the strain capacity is 0.1;

(2) annealing and insulating the cold-processed M42 wire rod for 20min at 700 ℃;

(3) continuously performing cold working on the annealed M42 wire rod, wherein the strain capacity is 0.15;

(4) annealing and insulating the cold-processed M42 wire for 15min at 720 ℃;

(5) continuously performing cold working on the annealed M42 wire rod, wherein the strain capacity is 0.2;

(6) annealing and insulating the cold-processed M42 wire rod for 10min at 740 ℃;

(7) the M42 wire was air cooled.

Example 2

(1) Carrying out cold working deformation on the M42 high-speed steel wire rod, wherein the strain capacity is 0.3;

(2) annealing and insulating the cold-processed M42 wire rod for 2min at 760 ℃;

(3) continuously performing cold working on the annealed M42 wire rod, wherein the strain capacity is 0.2;

(4) annealing and insulating the cold-processed M42 wire rod for 10min at 740 ℃;

(5) continuously cold-working the annealed M42 wire rod, wherein the strain is 0.1;

(6) annealing and insulating the cold-processed M42 wire for 15min at 720 ℃;

(7) the M42 wire was air cooled.

Example 3

(1) Carrying out cold working deformation on the M42 high-speed steel wire rod, wherein the strain capacity is 0.2;

(2) annealing and insulating the cold-processed M42 wire rod for 10min at 740 ℃;

(3) continuously performing cold working on the annealed M42 wire rod, wherein the strain capacity is 0.3;

(4) annealing and insulating the cold-processed M42 wire for 12min at 720 ℃;

(5) continuously performing cold working on the annealed M42 wire rod, wherein the strain capacity is 0.15;

(6) annealing and insulating the cold-processed M42 wire for 4min at 760 ℃;

(7) the M42 wire was air cooled.

Example 4

(1) Carrying out cold working deformation on the M42 high-speed steel wire rod, wherein the strain capacity is 0.15;

(2) annealing and insulating the cold-processed M42 wire rod for 15min at 720 ℃;

(3) continuously cold-working the annealed M42 wire rod, wherein the strain is 0.1;

(4) annealing and insulating the cold-processed M42 wire rod for 12min at 740 ℃;

(6) annealing and insulating the cold-processed M42 wire for 3min at 760 ℃;

(7) the M42 wire was air cooled.

Scanning electron micrographs of the M42 steel after the processing in examples 1 to 4 are shown in fig. 1 to 4, and it can be seen that in all of examples 1 to 4, a composite grain structure having both fine equiaxed grains and coarse equiaxed grains was obtained.

As a comparative example, M42 steel was treated by the conventional recrystallization annealing process and the conventional complete recrystallization annealing process, respectively, and the scanning electron micrographs of the treated M42 steel are shown in fig. 5 and 6, and it can be seen that the annealed structures of M42 steel treated by the conventional recrystallization annealing process and the conventional complete recrystallization annealing process are almost coarse equiaxed grains, the sizes of the grains are uniform, and a composite grain structure is not formed.

Fig. 7 is a scanning electron microscope image of M42 steel obtained after the cold deformation processing + annealing process of example 1 is performed once (i.e., after the step (2), the M42 wire is directly air-cooled), fig. 8 is a scanning electron microscope image of M42 steel obtained after the cold deformation processing + annealing process of example 1 is performed twice (i.e., after the step (4), the M42 wire is directly air-cooled), it can be seen that, in addition to coarse equiaxed grains, a certain amount of fine equiaxed grains are also obtained in fig. 7 and 8, and it can be seen from comparing fig. 1 and 7 to 8 that, as the number of cycles of the cold deformation processing + annealing process increases, the amount of fine equiaxed grains in the obtained M42 steel structure increases, the uneven recrystallization becomes more and more obvious, which illustrates that the effect of uneven recrystallization can be amplified by multiple times of repeated cycles, and a.

The tensile strength and total elongation of the M42 steel treated in examples 1-2 and the M42 steel treated in the comparative example by the recrystallization annealing process and the full recrystallization annealing process were tested and compared with the non-heat treated M42 steel, and the results were as follows:

the tensile strength of the M42 cold-drawn steel wire can reach about 1000MPa, but the total elongation is only about 6%;

the total elongation of the recrystallized annealed steel wire can reach about 18 percent, but the tensile strength is only about 780MPa (the structure is shown in figure 5); the total elongation of the completely recrystallized annealed steel wire is about 16 percent, and the tensile strength is about 800MPa (the structure is shown in figure 6);

the samples obtained after the process treatment of example 1 had tensile strengths and total elongations of 910MPa and 15%, respectively; the tensile strength and the total elongation of the sample obtained after the treatment by the process of example 2 were 925MPa and 13%, respectively;

it can be seen that the high speed steel sample with composite grain structure obtained by the process of the present invention can obtain better strong plasticity fit compared with the high speed steel sample with equiaxed grain structure obtained by recrystallization or complete recrystallization process, i.e. the plasticity is obviously improved (equivalent to and close to that of the fully recrystallized sample) while the high strength is maintained (greater than 900 MPa).

Claims

1. A high-speed steel processing method for obtaining a composite grain structure is characterized by comprising the following steps:

(1) controlling the strain amount to carry out cold machining on the high-speed steel wire rod; controlling the strain of the high-speed steel wire rod to be 0.1-0.3;

(2) controlling annealing of the cold-processed wire obtained in the step (1), wherein the annealing temperature is controlled to be 700-760 ℃, and the annealing time is 2-20 min;

(3) and (3) repeating the circulation steps (1) - (2), wherein the circulation frequency is not less than 3.