CN110724805A - A kind of preparation method of high-strength earthquake-resistant steel for construction - Google Patents

Abstract

The invention discloses a preparation method of high-strength anti-seismic steel for construction. The preparation method of high-strength anti-vibration steel for construction is as follows: Step 1: heating steel billets. In theory, the heating temperature of ordinary steel is the homogenization of austenite temperature. The present invention adopts a two-stage process in the process of rolling the steel. In the first stage, the original rolling process adopts an average reduction ratio of 14.58%, and the optimized process adopts an average reduction ratio of 12.42% to achieve the same intermediate billet. Thickness, in the second stage, the total reduction rate of the last three passes of the original rolling process is 40.44%, while that of the optimized process is 36.01%, and the rolling temperature is the same. The second stage is rolling in the non-recrystallized area of austenite. The ferrite grain size of the steel obtained by the optimized process is large. On the basis of ensuring strength and toughness, the ferrite grain should be properly coarsened, which can reduce the yield. The strength ratio ensures the stability of the steel, thereby improving the seismic performance of the steel.

Description

A kind of preparation method of high-strength earthquake-resistant steel for construction

technical field

The invention relates to the technical field of construction steel, in particular to a method for preparing high-strength seismic-resistant steel for construction.

Background technique

In the past 20 years, my country's high-rise building industry has made great progress, and a large number of high-rise and super-high-rise buildings with steel skeletons have emerged. In addition to toughness and weldability, high seismic resistance is also required. The catastrophic consequences caused by major earthquakes have prompted people to attach great importance to the seismic performance of high-strength construction steel. Generally speaking, the ratio of yield strength to tensile strength The lower the yield-strength ratio, the better the plastic deformation ability of the steel, the more seismic energy it can absorb, and the better its seismic resistance. Controlled rolling and controlled cooling are effective ways to improve the comprehensive performance of steel, but in practice In production, how to reduce the yield ratio while ensuring strength and toughness has always been a difficulty in steel rolling control.

In the rolling step of the existing steel, finer austenite grains are obtained by increasing the rolling reduction, which provides more positions for the deformation nucleus of austenite to ferrite, thereby refining the ferrite In the deformation process of the unrecrystallized area, due to the large amount of deformation in the last three passes, the size of the ferrite grains is finally made fine, and the ferrite grains are refined, which can increase the yield strength, and as a The volume fraction and lamellar spacing of hard phase pearlite are the main factors affecting the tensile strength. When the lamellar spacing and volume fraction of pearlite are basically the same, the tensile strength is also basically the same. The higher the yield strength is, the higher the yield ratio will be under the condition of basically the same tensile strength. Therefore, for steels with high yield ratio requirements, too fine ferrite grains are not conducive to the performance stability of the steel. sex.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a preparation method of high-strength seismic-resistant steel for construction, so as to solve the problems raised in the above background technology.

In order to achieve the above purpose, the present invention provides the following technical solutions: a preparation method of high-strength seismic-resistant steel for construction, and the preparation method of high-strength seismic-resistant steel for construction is as follows:

Step 1: Heating the steel billet. In theory, the heating temperature of ordinary steel is the austenite homogenization temperature. The purpose is to reduce the deformation resistance and make up for the temperature drop between processes. The heating temperature should be above 1250 °C, but, Because the temperature is too high, the intercalation force of the austenite grains may be weakened, and the structure will be excessively coarsened, which will lead to the deterioration of the final performance. Therefore, the heating temperature is about 1180 ° C, and the holding time in the furnace is more than 3 hours to ensure that The temperature difference of each part is less than 20℃;

Step 2: Rolling is carried out. In the first stage, the average reduction rate of 12.42% is used to achieve a certain intermediate blank thickness. In the second stage, the total reduction rate of the last three passes in the final product area is 36.01%. , the final temperature of rolling is controlled above 950 ℃, and the thickness of the intermediate embryo is about 2.5-4 times the thickness of the finished product;

Step 3: Controlled cooling of the refinished austenite. After the finishing rolling process, the steel leaves the finishing mill and is sent to the steel control cooling system. According to the steel type and the corresponding process, the steel air-cooling is controlled by the cooling system or the control system. Cooling, control the cooling system to cool with the corresponding amount of water and different cooling rates.

Preferably, after the steel is cast in the last pass of finished rolling, the steel is transported by the roller table and directly enters the ACC device. When the steel passes through the ACC device, the upper and lower sides are simultaneously sprayed with water for rapid cooling, so that the temperature of the steel is reduced from about 700 ～800℃ (i.e. austenite zone or bidirectional zone) drops rapidly to 600～650℃ (ACC controlled cooling), the thickness of steel above 25mm, the speed of passing through ACC device is about 0.3-1.0m/see; thickness For steel less than 25mm, the maximum passing speed can reach 3.0m/sec.

Preferably, when rolling in the austenite recrystallization zone, the reduction rate of each pass is required to be greater than the critical deformation rate, and the grains are continuously refined through recrystallization.

Preferably, if the steel is to be straightened, the straightening temperature is generally controlled above 600°C, and then slowly cooled between 600 and 400°C.

Preferably, for high-grade steel billets containing microalloying elements, the heating temperature is taken as an upper limit.

Preferably, the work-hardened austenite undergoes phase transformation at different cooling rates after rolling in the non-recrystallized zone.

Compared with the prior art, the beneficial effects of the present invention are: the present invention adopts a two-stage process in the process of rolling the steel, and in the first stage, the original rolling process adopts an average reduction ratio of 14.58%, and the optimized process The average reduction ratio of 12.42% was adopted to achieve the same intermediate billet thickness. In the second stage, the total reduction ratio of the last three passes of the original rolling process was 40.44%, while that of the optimized process was 36.01%, and the rolling temperature was the same. The first stage is the deformation of the austenite recrystallization zone, and the second stage is rolling in the austenite unrecrystallized zone. The average grain size of the steel obtained by the original rolling process is larger than that of the steel obtained by the optimized process. , the ferrite grain size of the steel obtained by the optimized process is larger, but the difference between the pearlite lamellae between the two is very small. Appropriate coarsening of the bulk grains can reduce the yield-to-strength ratio, ensure the stability of the steel, and thus improve the seismic performance of the steel.

Detailed ways

The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

The present invention provides a method for preparing high-strength anti-seismic steel for construction, and the method for preparing high-strength anti-vibration steel for construction is as follows:

Step 1: Heating the steel billet. In theory, the heating temperature of ordinary steel is the austenite homogenization temperature. The purpose is to reduce the deformation resistance and make up for the temperature drop between processes. The heating temperature should be above 1250 °C, but, Because the temperature is too high, the intercalation force of the austenite grains may be weakened, and the structure will be excessively coarsened, which will lead to the deterioration of the final performance. Therefore, the heating temperature is about 1180 ° C, and the holding time in the furnace is more than 3 hours to ensure that The temperature difference of each part is less than 20℃;

Step 2: Rolling is carried out. In the first stage, the average reduction rate of 12.42% is used to achieve a certain intermediate blank thickness. In the second stage, the total reduction rate of the last three passes in the final product area is 36.01%. , the final temperature of rolling is controlled above 950 ℃, and the thickness of the intermediate embryo is about 2.5-4 times the thickness of the finished product;

Step 3: Controlled cooling of the refinished austenite. After the finishing rolling process, the steel leaves the finishing mill and is sent to the steel control cooling system. According to the steel type and the corresponding process, the steel air-cooling is controlled by the cooling system or the control system. Cooling, control the cooling system to cool with the corresponding amount of water and different cooling rates.

In this embodiment, the average reduction ratio of 12.42% is adopted in the first stage of the rolling process, the total reduction ratio of the last three passes of the second stage is 36.01%, and the first stage is all deformed in the austenite recrystallization zone. The second stage is rolling in the non-recrystallized area of austenite. The average grain size of the steel obtained by the original rolling process is larger than that of the steel obtained by the optimized process. The ferrite grain size of the steel obtained by the optimized process is larger than that of the steel obtained by the optimized process. However, the difference between the two pearlite lamellae is very small. For products with high yield-strength ratio requirements, the ferrite grains should be properly coarsened on the basis of ensuring strength and toughness, which can reduce the yield-strength ratio. To ensure the stability of the steel, thereby improving the seismic performance of the steel.

Example 2

After the steel is cast in the last pass of finished rolling, it is transported by the roller table and directly enters the ACC device. When the steel passes through the ACC device, the upper and lower sides are simultaneously sprayed with water for rapid cooling, so that the temperature of the steel is about 700-800 ° C. (i.e. austenite zone or bidirectional zone) rapidly drops to 600-650℃ (ACC controlled cooling), steel with a thickness of more than 25mm, the speed of passing through the ACC device is about 0.3-1.0m/see; thickness less than 25mm For steel, the maximum passing speed can reach 3.0m/sec. In this embodiment, the biggest difference in the controlled cooling process parameters is the cooling rate and the temperature range of forced cooling (cooling start temperature and cooling stop temperature), different cooling rates and forced cooling The cooling temperature range has different effects on the microstructure of the steel during the rolling process and after the cooling process. For the steel that does not require accelerated cooling, water should not be sprayed when passing through the ACC device.

Example 3

When rolling in the austenite recrystallization zone, it is required that the reduction rate of each pass is greater than the critical deformation rate, and the grains are continuously refined through recrystallization. In this embodiment, the reduction rate of each pass is greater than the critical deformation rate, It can prevent mixed crystal phenomenon caused by partial recrystallization.

Example 4

To straighten the steel, the straightening temperature is generally controlled above 600°C, and then slowly cooled between 600 and 400°C. It is easy to precipitate, avoid the tendency of aging, cause cold bending inconsistency, and reduce impact toughness.

Example 5

For high-grade steel billets containing micro-alloying elements, the upper limit of the heating temperature is taken. In this embodiment, for high-grade steel billets containing micro-alloying elements, the upper limit of the heating temperature can ensure that the alloy elements are fully solid-solubilized and give full play to its subsequent delayed recrystallization. Temperature and precipitation strengthening effects.

Example 6

The work-hardened austenite after rolling in the non-recrystallized zone undergoes phase transformation at different cooling rates. In this example, the refined structure after this transformation improves the strength and toughness, and can correspondingly reduce the carbon The content and alloy content not only improve the mechanical properties of the steel, but also significantly improve the welding performance and the toughness of the welded part.

It will be apparent to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, but that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments are to be regarded in all respects as illustrative and not restrictive, and the scope of the invention is to be defined by the appended claims rather than the foregoing description, which are therefore intended to fall within the scope of the claims. All changes within the meaning and scope of the equivalents of , are included in the present invention. Any signs in the claims should not be construed as limiting the involved claim.

Claims (6)

1. a method for preparing high-strength anti-seismic steel for construction is characterized in that: the method for preparing high-strength anti-seismic steel for construction is as follows: Step 1: Heating the steel billet. In theory, the heating temperature of ordinary steel is the austenite homogenization temperature. The purpose is to reduce the deformation resistance and make up for the temperature drop between processes. The heating temperature should be above 1250 °C, but, Because the temperature is too high, the intercalation force of the austenite grains may be weakened, and the structure will be excessively coarsened, which will lead to the deterioration of the final performance. Therefore, the heating temperature is about 1180 ° C, and the holding time in the furnace is more than 3 hours to ensure that The temperature difference of each part is less than 20℃; Step 2: Rolling is carried out. In the first stage, the average reduction rate of 12.42% is used to achieve a certain intermediate blank thickness. In the second stage, the total reduction rate of the last three passes in the final product area is 36.01%. , the final temperature of rolling is controlled above 950 ℃, and the thickness of the intermediate embryo is about 2.5-4 times the thickness of the finished product; Step 3: Controlled cooling of the refinished austenite. After the finishing rolling process, the steel leaves the finishing mill and is sent to the steel control cooling system. According to the steel type and the corresponding process, the steel air-cooling is controlled by the cooling system or the control system. Cooling, control the cooling system to cool with the corresponding amount of water and different cooling rates. 2. The method for preparing high-strength seismic-resistant steel for construction according to claim 1, characterized in that: after the steel is cast in the last pass of finished rolling, the steel is transported directly into the ACC device by the roller table, and the steel passes through the ACC. When installed, the upper and lower sides are simultaneously sprayed with water for rapid cooling, so that the temperature of the steel drops rapidly from about 700 to 800 °C (ie, austenite zone or bidirectional zone) to 600 to 650 °C (ACC controlled cooling), and the thickness is 25mm. For the above steels, the speed of passing through the ACC device is about 0.3-1.0m/see; for steels with a thickness of less than 25mm, the maximum speed can reach 3.0m/sec. 3. The method for preparing high-strength seismic-resistant steel for construction according to claim 1, characterized in that: during rolling in the austenite recrystallization zone, the reduction ratio of each pass is required to be greater than the critical deformation rate, and Crystallization refines the grains. 4. The method for preparing high-strength seismic-resistant steel for construction according to claim 1, characterized in that: if the steel is to be straightened, the straightening temperature is generally controlled above 600°C, and then between 600 and 400°C. Cool slowly. 5 . The method for preparing high-strength seismic-resistant steel for construction according to claim 1 , characterized in that: for high-grade steel billets containing microalloying elements, the heating temperature is an upper limit. 6 . 6 . The method for preparing high-strength seismic-resistant steel for construction according to claim 1 , wherein the work-hardened austenite undergoes phase transformation under different cooling rates after rolling in the non-recrystallized zone. 7 .