WO2019001262A1

WO2019001262A1 - Process for forming, by means of warm ring rolling, high-carbon chromium bearing steel capable of structure spheroidization

Info

Publication number: WO2019001262A1
Application number: PCT/CN2018/090766
Authority: WO
Inventors: 钱东升; 杨俊�; 华林; 刘青龙; 王丰
Original assignee: 武汉理工大学
Priority date: 2017-06-28
Filing date: 2018-06-12
Publication date: 2019-01-03
Also published as: JP6698940B2; CN107138660A; JP2019532180A; CN107138660B

Abstract

Disclosed is a process for forming, by means of warm ring rolling, a high-carbon chromium bearing steel capable of structure spheroidization, the process comprising the following steps: S1. a ring blank is heated, in a heating furnace, to 10ºC-40ºC above the critical temperature Ac1 of the material, and holding the temperature for a period of time; S2. the heated ring blank is slowly cooled along with the furnace to 0ºC-50ºC below the critical temperature Ar1 of the material; S3. the rolling reduction is rationally designed and the rolling feed speed is selected such that the ring blank is roll-formed within a certain deformation amount and deformation temperature range. The method directly achieves structure spheroidization by means of warm ring rolling, can omit traditional spheroidization annealing, and obtains a more finely spheroidized structure, significantly reduces energy and time consumption, improves structure quality and reduces production costs.

Description

High carbon chromium bearing steel warm rolling ring forming method for realizing tissue spheroidization

Technical field

The invention belongs to the technical field of shaping processing, and in particular relates to a method for forming a high-carbon chromium bearing steel warm rolling ring for realizing spheroidization of a tissue.

Background technique

High carbon chromium bearing steel is the main steel for bearing parts, such as GCr15 bearing steel, which is widely used in bearing and outer ring production (referred to as bearing ring). As an advanced rotary plastic forming method for seamless ring parts (referred to as ring parts), the rolling ring has gradually replaced the traditional forging forming method with the advantages of energy saving, material saving, high quality and high efficiency. It is widely used and widely recognized in the manufacture of parts. For high carbon chromium bearing steel ring parts, taking the typical GCr15 bearing ring as an example, the current rolling ring method used in industrial production includes cold rolling ring and hot rolling ring. The former is mainly used for medium and small bearing rings at room temperature and cold forming. It is usually used for thermoforming of medium and large bearing ring forging temperature zones.

Due to the low plasticity, high hardness and strength, and poor cold forming and cutting performance of high carbon chromium bearing steel, spheroidizing annealing has always been an indispensable important process in the production of high carbon chromium bearing steel ring forging or rolling ring. By spheroidizing annealing the ring blank or the ring forging, the carbide in the sheet-like pearlite structure is spheroidized to form a granular pearlite structure, thereby improving plasticity, reducing hardness and strength, and meeting the manufacturing process requirements. For example, in the production of cold-rolled rings, spheroidal annealing of the ring blank is required to improve the cold-plastic processing performance; in the hot-rolled ring and forging production, the ring forging is subjected to spheroidizing annealing to improve the cutting performance. However, the isothermal spheroidizing annealing process commonly used in the industrial production of high carbon chromium bearing steel ring parts generally takes more than ten hours, which not only has a long cycle and high energy consumption, but also easily leads to coarse carbide particles, surface decarburization and oxidation. Large, will have a genetic impact on the quality of subsequent processing and final heat treatment. Although the current research on rapid spheroidizing annealing of high carbon chromium bearing steel has been reported, it has not obtained practical industrial applications, especially in the production of high carbon chromium bearing steel ring parts, still using the traditional spheroidizing annealing process to reduce costs. And the quality has caused a lot of restrictions. Therefore, in the face of the current development trend of energy-saving emission reduction and high value-added production in manufacturing, it is urgent to solve the problem of spheroidizing annealing of the above-mentioned high carbon chromium bearing steel ring.

Summary of the invention

In view of the above situation, an object of the present invention is to provide a method for forming a high carbon chromium bearing steel warm rolling ring which realizes spheroidization of a material, which is directly spheroidized by a deformation of a warm rolling ring at a temperature lower than the forging temperature of the material. Forming-spheroidizing integration eliminates the need for traditional spheroidizing annealing processes to increase efficiency and reduce energy consumption.

The technical solution adopted by the present invention to solve the technical problem thereof is:

A high carbon chromium bearing steel warm rolling ring forming method for realizing spheroidization, the method comprising the following steps:

S1, low temperature austenitizing heating: the processed ring blank is placed in a heating furnace and heated to a temperature slightly higher than the material critical temperature Ac ₁ and kept for 5 to 10 minutes;

S2, slow cooling in the furnace: the ring blank after the heat preservation is slowly cooled in the heating furnace to slightly lower than the material critical temperature Ar ₁ , and the cooling rate is controlled at 100 ° C / h ~ 200 ° C / h;

S3, warm rolling forming: the cooled ring blank is quickly transferred from the heating furnace to the rolling ring machine for rolling, the ring blank deformation amount is controlled to be 40% to 70%, and the finishing rolling temperature is controlled within 100 ° C below Ar ₁ .

According to the above technical solution, in step S1, the ring blank is heated in a heating furnace to Ac ₁ or more and 10 ° C to 40 ° C.

According to the above technical solution, in step S2, the ring blank is cooled in a heating furnace to a temperature of 0 ° C to 50 ° C below Ar ₁ .

According to the above technical solution, in step S3, the ring blank temperature is monitored in real time during the rolling process, and when the ring billet temperature is lower than the finish rolling temperature, the rolling is terminated immediately, and the ring blank is returned to the furnace to be heated to the preset initial rolling temperature. Rolling continues until it is formed into a target ring.

The invention has the following beneficial effects: the invention obtains effective spheroidization conditions during the warm forming process under the critical temperature, based on suitable rolling process conditions, thereby realizing deformation and simultaneous spheroidization: firstly through suitable Heating conditions to obtain incomplete and uneven austenite structure; then under suitable cooling conditions, the carbide particles are abnormally decomposed from the supercooled austenite to inhibit the normal decomposition of the carbide layer; The deformation condition promotes the diffusion and aggregation of carbon elements to the carbide particles through temperature and stress, and causes the partially formed carbide layer to be broken and spheroidized, and finally obtains the globalized structure after rolling. Since the above-mentioned tissue spheroidization process is completed in the low-temperature rapid rolling process, the carbide particles are not sufficiently matured and grown to be fine and uniform, the rolling temperature is low, and the surface has no obvious oxidation and decarburization. Therefore, the present invention passes the warm rolling. Ring deformation directly realizes spheroidization, which can eliminate spheroidizing annealing. Compared with cold rolling ring and hot rolling ring, spheroidizing annealing is required, which significantly reduces energy consumption and improves efficiency, and has fine carbide particles and good surface quality. Conducive to the quality of subsequent processing and final heat treatment, it has the beneficial effect of shortening the process flow, reducing production cost, improving production efficiency and improving product quality.

DRAWINGS

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

1 is a schematic view of a process of an embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In a preferred embodiment of the present invention, a method for forming a high carbon chromium bearing steel warm rolling ring for achieving spheroidization, as shown in FIG. 1, the method comprises the following steps:

S1, low temperature austenitizing heating: the processed ring blank is placed in a heating furnace and heated to a temperature slightly higher than the material critical temperature Ac1, and kept for 5 to 10 minutes;

S2, slow cooling in the furnace: the ring blank after the heat preservation is slowly cooled in the heating furnace to slightly lower than the critical temperature Ar1 of the material, and the cooling rate is controlled at 100 ° C / h ~ 200 ° C / h;

S3, warm rolling forming: the cooled ring blank is quickly transferred from the heating furnace to the rolling ring machine for rolling. According to the size of the target ring part, the processing range of the ring rolling machine and the force energy conditions, the rolling ratio and the selective rolling are rationally designed. The feed rate is controlled so that the ring blank deformation is controlled at 40% to 70% (the ring blank deformation amount is calculated by the ring blank wall thickness reduction rate), and the finish rolling temperature is controlled within 100 ° C below Ar1, and the ring blank is in the deformation. Roll forming in the range of volume and deformation temperatures.

In a preferred embodiment of the invention, in step S1, the ring blank is heated in a heating furnace to above Ac1 above 10 ° C to 40 ° C.

In a preferred embodiment of the invention, in step S2, the ring blank is cooled in a heating furnace to below 0 ° C to 50 ° C below Ar 1 .

In a preferred embodiment of the present invention, in step S3, the ring blank temperature is monitored in real time during the rolling process (specifically, the temperature of the ring blank is strictly monitored by the temperature measuring device), and the ring blank is immediately terminated when the temperature is lower than the finishing temperature. After rolling, the ring blank is returned to the furnace and heated to a preset initial rolling temperature, and then the rolling is continued until it is formed into a target ring member.

The invention is further illustrated by the following two examples.

Example 1

Taking a certain size of GCr15 high carbon chromium bearing steel ring as an example, the method for forming a warm rolling ring for spheroidizing comprises the following steps:

S1, low temperature austenitizing heating: the ring blank is heated to 780 ° C (Ac1 is about 750 ° C) in a box type electric resistance furnace, and kept for 10 minutes;

S2, slow cooling in the furnace: cooling the ring blank at the cooling rate of 200 ° C / h in the furnace to 650 ° C (Ar1 is about 700 ° C);

S3, warm rolling forming: the ring blank which reaches the preset initial rolling temperature is quickly transferred from the heating furnace to the rolling mill, and the ring blank is above 600 ° C under the conditions of suitable rolling ratio and rolling feed rate. The temperature is formed into a target ring by rolling deformation of 40% deformation, and the target ring is then air-cooled.

Example 2

Taking a certain size GCr15SiMn high carbon chromium bearing steel ring member as an example, the method for forming a warm rolling ring for forming a spheroidization comprises the following steps:

S1, low temperature austenitizing heating: the ring blank is heated to 790 ° C (Ac1 is about 770 ° C) in a box type electric resistance furnace, and kept for 5 minutes;

(2) Slow cooling in the furnace: the ring blank which is kept in heat is cooled in the furnace to 710 ° C at a cooling rate of 200 ° C / h (Ar1 is about 710 ° C);

(3) Warm rolling forming: the ring blank which reaches the preset initial rolling temperature is quickly transferred from the heating furnace to the rolling mill, and the ring blank is at 610 ° C under the conditions of suitable rolling ratio and rolling feed rate. The above temperature is formed into a target ring by rolling deformation of 70% deformation, and the target ring is then air-cooled.

Comparing the spheroidized structure obtained by the target ring member obtained by the above two embodiments with the spheroidized structure obtained by ordinary spheroidizing annealing, the average diameter of the warm rolled ring carbide particles is about 0.25 μm, and the ordinary spheroidizing annealing carbonization The average particle diameter of the particles is about 0.46 μm. It can be seen that the method of forming the high carbon chromium bearing steel by using the warm rolling ring forming method of the invention can not only refine the carbide particles and improve the quality of the spheroidized structure.

The present invention is also applicable to other high carbon chromium bearing steel material ring members, and the method thereof is the same as that of the above embodiment, and the effects are also the same, and the examples are not enumerated here.

It is to be understood that those skilled in the art will be able to make modifications and changes in accordance with the above description, and all such modifications and variations are intended to be included within the scope of the appended claims.

Claims

A high carbon chromium bearing steel warm rolling ring forming method for realizing tissue spheroidization, characterized in that the method comprises the following steps:

S1, low-temperature austenitizing heating: the processed ring blank is placed in a heating furnace and heated to a temperature slightly higher than the material critical temperature Ac 1 and kept for 5 to 10 minutes;

S2, slow cooling in the furnace: the ring blank after the heat preservation is slowly cooled in the heating furnace to slightly lower than the material critical temperature Ar 1 , and the cooling rate is controlled at 100 ° C / h ~ 200 ° C / h;

S3, warm rolling forming: the cooled ring blank is quickly transferred from the heating furnace to the rolling ring machine for rolling, the ring blank deformation amount is controlled to be 40% to 70%, and the finishing rolling temperature is controlled within 100 ° C below Ar 1 .
The method for forming a high carbon chromium bearing steel warm rolling ring for achieving spheroidization according to claim 1, wherein in step S1, the ring blank is heated in a heating furnace to Ac 1 or more and 10 ° C to 40 ° C.
The method for forming a high carbon chromium bearing steel warm rolling ring for realizing spheroidization according to claim 1, wherein in step S2, the ring blank is cooled in a heating furnace to 0 ° C to 50 ° C below Ar 1 .
The method for forming a high carbon chromium bearing steel warm rolling ring for realizing spheroidization according to claim 1, wherein in step S3, the ring blank temperature is monitored in real time during the rolling process, when the ring blank temperature is lower than the final The rolling is immediately terminated at the rolling temperature, and the ring blank is returned to the furnace to a preset initial rolling temperature and then the rolling is continued until it is formed into a target ring member.