CN108486496B

CN108486496B - Controlled rolling and controlled cooling process method for superfine austenite grains of Ti-Zr-Mo composite microalloyed steel

Info

Publication number: CN108486496B
Application number: CN201810204975.4A
Authority: CN
Inventors: 曹建春; 刘鹏程; 周晓龙; 阴树标; 杨银辉; 高鹏
Original assignee: Kunming University of Science and Technology
Current assignee: Kunming University of Science and Technology
Priority date: 2018-03-13
Filing date: 2018-03-13
Publication date: 2020-11-27
Anticipated expiration: 2038-03-13
Also published as: CN108486496A

Abstract

A controlled rolling and controlled cooling process method of ultrafine austenite grains of Ti-Zr-Mo composite microalloyed steel adopts Ti-Zr-Mo composite microalloyed steel with the Ti content of 0.01-0.5%, the Zr content of 0.01-0.5%, the Mo content of 0.01-0.5% and the C content of 0.01-0.5%. Heating the Ti-Zr-Mo composite microalloyed steel to 1150-1250 ℃, preserving heat for 300s, cooling to 1000-1100 ℃, starting first-pass rolling with the strain rate of 1-10 s^‑1And the reduction is 35%. And (3) after the interval is 1-10 s, carrying out second pass rolling, wherein the rolling parameters are as follows: strain rate of 1-10 s^‑1The reduction was 30%. And after 1-10 s of interval, carrying out a third rolling, wherein the rolling parameters are as follows: strain rate of 1-10 s^‑1And the reduction is 20%. And controlling the finishing temperature to be more than 1000 ℃, and quickly spraying water for cooling to room temperature after 1-50 s. The method of the invention is used for promoting complete austenite recrystallization for many times through three times of rolling, and the grain size is thinned to 7-15 mu m from 100 mu m to obtain a uniform superfine austenite grain structure.

Description

Controlled rolling and controlled cooling process method for superfine austenite grains of Ti-Zr-Mo composite microalloyed steel

Technical Field

The invention belongs to the technical field of steel rolling, and particularly relates to a controlled rolling and controlled cooling process method for ultrafine austenite grains of Ti-Zr-Mo composite microalloyed steel.

Background

Fine grain strengthening is the only method for improving the material plasticity and toughness while improving the material strength, so the research on grain refinement is always a focus. The prior austenite grain size of Ti (titanium) microalloyed steel has great influence on the yield strength, toughness, plasticity and the like of steel, so that the grain size control of austenite in the rolling stage has important significance.

At present, researchers in various countries develop various methods for refining grains under laboratory conditions, such as equal channel angular pressing, cumulative pack rolling, high-pressure twisting and the like, but due to the large amount of strain required by the methods, the further application of the methods in practical production is limited. From the view point of industrial application, a feasible approach for refining grains is to perform small reduction and large strain rate deformation in an austenite recrystallization region in a controlled rolling stage to promote multiple austenite recrystallization, and combine the small austenite recrystallization grains with the function that TiC (titanium carbide) precipitated by deformation induction can pin austenite grain boundaries to obtain fine austenite recrystallization grains. Zr (zirconium) promotes the precipitation of TiC, and makes the size of the precipitated phase fine. Mo (molybdenum) can inhibit the disappearance of dislocation at high temperature, increase the density of the dislocation and provide more nucleation sites for TiC. In view of the above, the invention provides a controlled rolling and controlled cooling process method for ultrafine austenite grains of Ti-Zr-Mo composite microalloyed steel.

Disclosure of Invention

The invention provides a controlled rolling and controlled cooling process method of ultrafine austenite grains of Ti-Zr-Mo composite microalloyed steel. The invention obtains the uniform and fine austenite grain structure by designing alloy components, rolling in combination with different rolling reduction and different strain rates, and controlling the structure relationship among each pass and the austenite recrystallization process.

The invention relates to a controlled rolling and controlled cooling process method of ultrafine austenite grains of Ti-Zr-Mo composite microalloyed steel, which comprises the following steps:

1. the invention adopts Ti-Zr-Mo composite microalloyed steel with 0.01-0.5 percent of Ti, 0.01-0.5 percent of Zr, 0.01-0.5 percent of Mo and 0.01-0.5 percent of C.

2. Heating the Ti-Zr-Mo composite microalloyed steel to 1150-1250 ℃, preserving heat for 300s, cooling to 1000-1100 ℃, and starting first-pass rolling, wherein the first-pass rolling parameters are as follows: strain rate of 1-10 s^-1The reduction amount is 35 percent;

3. and (3) after the interval is 1-10 s, performing second-pass rolling, wherein the second-pass rolling parameters are as follows: strain rate of 1-10 s^-1The reduction was 30%.

4. And (4) after 1-10 s of interval, carrying out third rolling, wherein the third rolling parameters are as follows: strain rate of 1-10 s^-1And the reduction is 20%.

5. And controlling the finishing temperature to be more than 1000 ℃, preserving the heat for 1-50 s, and then quickly spraying water for cooling to the room temperature.

The process principle of the process scheme is that multiple times of austenite recrystallization is triggered through multiple times of different rolling reduction and different strain rates, and the growth of recrystallized austenite is prevented by combining with TiC induced by deformation, so that austenite grains are fully superfine.

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

1. the austenite grains are superfine while the austenite is homogenized by controlling the rolling reduction, strain rate, temperature and time interval of pass in the steel rolling process.

And 2, rolling the Ti-Zr-Mo composite microalloyed steel for three times at different rolling reduction and different strain rates to promote complete austenite recrystallization for many times, so that the size of austenite grains is refined from 100 mu m to 7-15 mu m, and the size of the austenite grains is obviously refined.

Drawings

FIG. 1 shows austenite grain structure morphology of Ti-Zr-Mo composite micro-alloyed steel without rolling;

FIG. 2 shows the austenite grain structure of Ti-Zr-Mo composite micro-alloyed steel after three rolling passes.

Detailed Description

Heating Ti-Zr-Mo composite microalloyed steel to 1200 ℃, preserving heat for 300s, then cooling to 1050 ℃, starting first-pass rolling with the strain rate of 10s^-1And the reduction is 35%. After the interval of 10s, carrying out second-pass rolling, wherein the second-pass rolling parameters are as follows: strain rate 10s^-1The reduction was 30%. After the interval of 10s, carrying out third rolling, wherein the parameters of the third rolling are as follows: strain rate 5s^-1And the reduction is 20%. The finishing temperature is controlled to be above 1000 ℃, and after the temperature is kept for 30s, water is rapidly sprayed to cool to the room temperature. The average grain size obtained by the three passes of rolling was about 10 μm (as shown in FIG. 2), which is comparable to that obtained by the previous rollingThe grains are significantly refined compared to the rolled structure (as shown in fig. 1).

The Ti-Zr-Mo composite microalloyed steel preferably comprises the following components: 0.01 to 0.5% Ti, 0.01 to 0.5% Zr, 0.01 to 0.5% Mo, 0.01 to 0.5% C (carbon). The ingredients are further preferably: ti content of 0.1%, Zr content of 0.05%, Mo content of 0.05% and C content of 0.05%.

Here, the shape of the Ti-Zr-Mo composite microalloyed steel is not limited, and examples thereof include round and square billets.

The heating device may be, for example, a heating furnace, and the rolling device may be, for example, a four-roll double-stand rolling mill.

As Zr can reduce the hot brittleness of the Ti-Zr-Mo composite microalloyed steel, the Ti-Zr-Mo composite microalloyed steel can be greatly deformed at a high temperature stage to obtain more deformation energy storage, and sufficient energy is provided for austenite recrystallization. The Ti-Zr-Mo composite microalloyed steel is subjected to deformation at different rolling reduction and different strain rates in an austenite recrystallization zone, so that the recrystallization of austenite is completed for multiple times in the rolling process, and the growth of recrystallized austenite can be effectively prevented and the size of austenite grains can be refined by combining the action of TiC precipitated by deformation induction and pinning an austenite grain boundary. Meanwhile, Mo can inhibit the disappearance of dislocation at high temperature, increase the density of dislocation and provide more precipitation positions for TiC. Zr can promote the precipitation of TiC and refine the size of the precipitated phase.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. A controlled rolling and controlled cooling process method of ultrafine austenite grains of Ti-Zr-Mo composite microalloyed steel is characterized by comprising the following steps:

1) providing Ti-Zr-Mo composite microalloyed steel with 0.01-0.5% of Ti, 0.01-0.5% of Zr, 0.01-0.5% of Mo and 0.01-0.5% of C;

2) heating the Ti-Zr-Mo composite microalloyed steel to 1150-1250 ℃, preserving heat for 300s, cooling to 1000-1100 ℃, and starting first-pass rolling, wherein the first-pass rolling parameters are as follows: strain rate of 1-10 s^-1The reduction amount is 35 percent;

3) and (3) after the interval is 1-10 s, performing second-pass rolling, wherein the second-pass rolling parameters are as follows: strain rate of 1-10 s^-1The reduction amount is 30 percent;

4) and (4) after 1-10 s of interval, carrying out third rolling, wherein the third rolling parameters are as follows: strain rate of 1-10 s^-1The reduction amount is 20 percent;

5) controlling the finishing temperature to be more than 1000 ℃, preserving the heat for 1-50 s, and then quickly spraying water for cooling to the room temperature;

the austenite grain size is thinned from 100 mu m to 7-15 mu m.