CN109158432B

CN109158432B - Rolling method for improving compactness of bloom after pressing of convex roller

Info

Publication number: CN109158432B
Application number: CN201811030011.9A
Authority: CN
Inventors: 祭程; 朱苗勇; 石彪; 刘宗辉
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2018-09-05
Filing date: 2018-09-05
Publication date: 2020-04-03
Anticipated expiration: 2038-09-05
Also published as: CN109158432A

Abstract

The invention relates to a rolling method, in particular to a rolling method for improving the density of a bloom after a convex roller is pressed down. The technical scheme of the invention is as follows: a rolling method for improving the compactness of a bloom after the reduction of a convex roller controls the initial rolling temperature of a casting blank to be 1100-1200 ℃; during rough rolling, the rolling direction of the first pass is transverse rolling, and the rolling pass of the rough rolling is 11 times. The rolling method for improving the density of the bloom after the convex roller is pressed down can obviously improve the center porosity of the rolled billet and improve the center density of the rolled billet.

Description

Rolling method for improving compactness of bloom after pressing of convex roller

Technical Field

The invention relates to a rolling method, in particular to a rolling method for improving the density of a bloom after a convex roller is pressed down.

Background

The defects of central shrinkage cavity, looseness and the like of the casting blank can be obviously improved by carrying out a heavy reduction process at the solidification tail end in the continuous casting process of the bloom. Before the heavy reduction process is carried out, the pulling straightening roller needs to be transformed into a convex roller, and a groove with the depth of more than 10mm is formed on the surface of a casting blank after the heavy reduction process is carried out by the pulling straightening roller, as shown in figure 1. In the rolling process, because the bosses on two sides of the groove are not effectively supported by the central sunken area, the central quality defect of the concave blank cannot be effectively improved in the subsequent rolling process, and the groove is rolled to be flat as soon as possible in the rough rolling process.

The patent application CN201410414400.7 "rolling process method of ultra-thin and ultra-wide steel plate" ensures that the soaking temperature of a steel-pushing type heating furnace is controlled at 1200-1250 ℃, the soaking time is not less than 60 minutes, and the temperature difference between the head and the tail of the steel billet is not more than 30 ℃; dog bone rolling is adopted in the last pass of the rough rolling forming stage and the widening stage respectively; the diameter of the lower roll of the flat roll type working roll with the edge part provided with the chamfer is 2-5mm larger than that of the upper roll of the working roll; the centering difference of the pusher is within 10 mm; the rolling passes of the roughing mill are controlled to be rolled according to 8-10 passes and the finish rolling is controlled to be rolled according to 6-8 passes, and the reduction of the last three passes of the finish rolling is gradually reduced and the reduction rate of the last three passes of the finish rolling is controlled to be 10-15%; two 11-roll straightening machines were used for straightening. The method is mainly used for rolling the ultrathin ultra-wide steel plate, and is not suitable for the rolling process of the concave parison.

Patent application CN201410298490.8 "a rolling process for controlling decarburization of a 42CrMo steel bloom hot-rolled wire rod", wherein a 42CrMo steel bloom is cogging, and the temperature, time and residual oxygen amount of a cogging heating furnace are controlled; grinding the cogging steel billet, and grinding the surface and the corner; rolling, wherein the rolling heating furnace controls the temperature, time, residual oxygen amount and residence time of each steel billet; the rough rolling temperature is 980-1020 ℃, the finish rolling temperature is 900 ℃, and the spinning temperature is 850 ℃; after rolling, rapidly cooling the steel plate to 600-650 ℃ at a cooling rate of more than 5-15 ℃/S, keeping the temperature to about 300-350 ℃, and collecting the steel plate, wherein the speed of a roller way is controlled to be 0.4-0.5 m/S, and the steel plate is mainly used for conventional large square billets but is not suitable for the rolling process of concave billets.

Disclosure of Invention

The invention provides a rolling method for improving the density of a large square billet after the pressing of a convex roller, which can obviously improve the center porosity of a rolled billet and improve the center density of the rolled billet.

The technical scheme of the invention is as follows: a rolling method for improving the compactness of a bloom after the reduction of a convex roller controls the initial rolling temperature of a casting blank to be 1100-1200 ℃; during rough rolling, the rolling direction of the first pass is transverse rolling, and the rolling pass of the rough rolling is 11 times.

The invention has the beneficial effects that:

1. the initial rolling temperature of the casting blank is controlled to be 1100-1200 ℃, so that the phenomenon that effective reduction cannot be generated due to too low temperature and the phenomenon of overburning can be generated due to too high temperature can be prevented.

2. During rough rolling, the first rolling direction is transverse rolling, the grooves of the casting blank can be flattened firstly, so that the whole casting blank is effectively supported in the subsequent rolling process, and the central defect of the casting blank is reduced.

3. The rough rolling passes are 11 times, and the change of the rolling direction of the first pass can be matched, so that the existing rolling mill can finish rolling.

4. By controlling the initial rolling temperature and improving the rough rolling schedule, the invention can reduce the center loosening defect of the rolled blank, improve the internal quality of the rolled blank, further improve the center density of the rolled blank, and well meet the use requirements of large-specification round steel.

Drawings

Fig. 1 is a schematic cross-sectional view of a concave blank.

Detailed Description

Comparative example 1

The female parison was rolled using a conventional rolling process:

the size of the continuous casting billet is 320mm multiplied by 425mm, the wide surface of the continuous casting billet is provided with a groove with the depth of 13mm, the steel type is No. 45, the initial rolling temperature is 1113 ℃ after surface iron oxide sheets are removed by high-pressure water, the conventional rolling system shown in the following table 1 is adopted in the rolling process, and then the rolling is carried out to form round steel, wherein the specification of the rolled round steel is 150 mm.

TABLE 1 conventional roughing Rolling System

After rolling, 45# steel round steel is sampled and is subjected to low-power inspection to detect the internal quality of the round steel, and inspection results show that the horizontal low-power central loosening defect of the round steel is graded as 1.5, no obvious crack exists, the longitudinal low-power loosening width of the round steel is 60mm, ultrasonic flaw detection is performed on the round steel, and the ultrasonic flaw detection qualified rate of detection results is 80%.

Example 1

The concave blank is rolled by using a rolling method for improving the density of the pressed large square blank by a convex roller:

the size of the continuous casting billet is 320mm multiplied by 425mm, the wide surface of the continuous casting billet is provided with a groove with the depth of 13mm, the steel type is No. 45, the initial rolling temperature is 1127 ℃ after surface oxidized iron sheets are removed by high-pressure water, the rolling schedule shown in the following table 2 is adopted in the rolling process, and then the rolling is carried out to form round steel, wherein the specification of the rolled round steel is 150 mm.

TABLE 2 improved rough rolling schedule

After rolling, 45# steel round steel is sampled and is subjected to low-power inspection to detect the internal quality of the round steel, and inspection results show that the round steel does not have obvious shrinkage porosity and central crack defects at the transverse low power, the longitudinal low-power porosity width of the round steel is 30mm, the round steel is subjected to ultrasonic flaw detection, and the ultrasonic flaw detection qualified rate of the detection results is 100%.

Example 2

the size of the continuous casting billet is 320mm multiplied by 425mm, the wide surface of the continuous casting billet is provided with a groove with the depth of 12mm, the steel type is No. 45, the initial rolling temperature is 1150 ℃ after surface iron oxide sheets are removed by high-pressure water, the rolling schedule shown in the table 2 is adopted in the rolling process, and then the rolling is carried out to form round steel, wherein the specification of the rolled round steel is 150 mm.

After rolling, 45# steel round steel is sampled and is subjected to low-power inspection to detect the internal quality of the round steel, and inspection results show that the round steel does not have obvious shrinkage porosity and central crack defects in the transverse low-power mode, the longitudinal low-power porosity width of the round steel is 28mm, ultrasonic flaw detection is performed on the round steel, and the ultrasonic flaw detection qualified rate of the detection results is 100%.

Example 3

the size of the continuous casting billet is 320mm multiplied by 425mm, the wide surface of the continuous casting billet is provided with a groove with the depth of 15mm, the steel type is No. 45, the initial rolling temperature is 1137 ℃ after surface iron oxide sheets are removed by high-pressure water, the rolling schedule shown in the table 2 is adopted in the rolling process, and then the rolling is carried out to form round steel, wherein the specification of the rolled round steel is 180 mm.

After rolling, 45# steel round steel is sampled and is subjected to low-power inspection to detect the internal quality of the round steel, and inspection results show that the round steel does not have obvious shrinkage porosity and central crack defects in the transverse low-power mode, the longitudinal low-power porosity width of the round steel is 40mm, ultrasonic flaw detection is performed on the round steel, and the ultrasonic flaw detection qualified rate of the detection results is 100%.

As can be seen from comparison between examples 1-3 and comparative example 1, the concave billet rolled by the rolling method for improving the density of the bloom after the convex roller is pressed down has the advantages that the central porosity is obviously reduced, the central density is obviously improved, and the ultrasonic flaw detection qualified rate is 100%.

Claims

1. A rolling method for improving the compactness of a bloom after the reduction of a convex roller is characterized in that the initial rolling temperature of a casting blank is controlled to be 1100-1200 ℃; during rough rolling, the rolling direction of the first pass is transverse rolling, and the rolling pass of the rough rolling is 11 times.