CN105665443B - A kind of rolling mill practice of wide and heavy plate mill production Limit specifications pipe line steel - Google Patents

Abstract

The invention relates to a rolling process for producing limit specification pipeline steel by a wide and thick plate rolling mill, which belongs to the technical field of steel rolling. By selecting a reasonable billet, the thickness of the size is 150-200mm; increasing the heating temperature and finishing rolling temperature control, optimizing the rolling schedule, adjusting the cooling water of the roll body, speeding up the rolling rhythm, controlling the finishing rolling speed to 4-7m/s, straightening It can be achieved through direct process improvement and arranging a reasonable rolling plan. The advantage is that it effectively solves the shape problem of thin-gauge pipeline steel plates, achieves a high rolling hit rate and yield rate, and can stably and mass-produce qualified products.

Description

A rolling process for producing limit specification pipeline steel in a wide and thick plate rolling mill

technical field

The invention belongs to the technical field of steel rolling, and in particular relates to a rolling process for producing limit specification pipeline steel by a wide and thick plate rolling mill. In particular, it relates to a rolling process for producing pipeline steel with a thickness of 7-10 mm and a thin specification by using a 4300 mm double-stand wide and thick plate rolling mill.

Background technique

Thin-gauge pipeline steel plates are usually produced on hot rolling mills and used after Kaiping treatment. However, for pipeline steel for regional urban pipeline networks and some special-purpose pipeline steel, it is often required to be flat and the thickness of the steel plate is relatively thin. It is difficult to guarantee the shape of the coiled plate after being flattened, and the narrow width of the coiled plate often results in a large amount of welding and high cost. The stress is large and unevenly distributed. At present, when producing thin-gauge pipeline steel with a thickness of less than 10mm on a double-stand wide and thick plate rolling mill, in view of the consideration of the yield rate and limited by the size of the billet, it can only be produced by double-size, and the thickness direction of the rolled piece is constantly changing during the rolling process. As the length decreases, the length continues to increase, and the temperature drop of the rolled piece becomes faster and faster, resulting in an increase in the temperature non-uniformity in the length direction. Uneven temperature in the length direction of the rolled piece leads to unstable rolling state, and problems such as plate shape, scratching, and performance fluctuations of the steel plate are prone to occur, and the scrap rate is high. Therefore, it is difficult for medium and heavy plate rolling mills to produce such thin-gauge pipeline steel in batches and stably.

After searching, the patent document of Chinese patent application number 201210189869.6 discloses a production process of thin-gauge pipeline steel in a double-stand medium-thick plate rolling mill. Thick, billet size is more restrictive.

Contents of the invention

The purpose of the present invention is to provide a rolling process for producing limit specification pipeline steel by wide and heavy plate rolling mills, which solves the problems of poor plate shape, high scrap rate and performance fluctuation of steel plates that are easily occurred in the production of thin gauge pipeline steel. Realize the ability to batch and stably roll high-quality thin-gauge pipeline steel on thick plate rolling mills.

A rolling process for producing limit specification pipeline steel with a wide and thick plate rolling mill, the specific steps and parameters are as follows:

1. The thickness of the steel plate continuous casting slab is 150-200mm, and the rolling length of the steel plate is ≤40m.

2. The billet heating temperature is controlled at 1200°C to 1230°C. At the same time, it is necessary to control the temperature difference between the upper and lower surfaces of the billet. The temperature difference between the upper and lower surfaces of the billet should be controlled within 30°C, and the final rolling temperature should be controlled at 860°C to 920°C.

3. Arrange the rolling of the steel plate with the target thickness in the middle and late stages of the rolling period. Before rolling the steel plate with the target thickness, arrange 8 to 12 steel plates with similar specifications for rolling, so that the model self-adaptive coefficient approaches the rolling of the target thickness. control status.

4. Before rolling the target steel plate, turn off the cooling water of the input and output roller table of the rolling mill to reduce the temperature drop; the total rolling pass is 12-14 passes, and the thickness of the intermediate billet is set at 40-60mm; No more than 7 passes.

5. By controlling the distribution and amount of cooling water on the roll body, the temperature drop of the steel plate can be slowed down and the purpose of controlling the roll shape can be achieved at the same time. Before rolling the target thickness steel plate, adjust the opening amount of the cooling water in the middle of the work roll body to 70-80%, and adjust it to 40-50% on both sides.

6. In order to reduce the temperature drop and ensure the stability of the finishing rolling process, after the rough rolling, the intermediate billet will quickly enter the finishing rolling mill through the intermediate connecting roller table, and the finishing rolling speed is 4-7m/s; For the occurrence of bending at the tail of the steel plate after production, the steel throwing distance before the finishing mill is 1.8-2m, and the steel throwing distance after the mill is set at 3.3-3.5m.

7. The last 3 passes of finish rolling are rolled using the principle of equal-proportional crown. The rolling force of the last 3 passes decreases step by step, and the reduction decreases step by step. The reduction of the final pass is controlled at 1.1-1.6mm.

8. Turn off the cooling water of the front and rear rollers of the straightening machine to slow down the temperature drop of the steel plate. In order to increase the bending curvature of the steel plate and improve the shape of the plate, the inlet guide roller is lifted by 1.4-1.6mm during straightening.

The advantages of the present invention are: aiming at the difficulties in the production process of thin-gauge pipeline steel, by selecting a reasonable billet size, increasing the heating temperature and final rolling temperature control, optimizing the rolling schedule, adjusting the cooling water of the roll body, accelerating the rolling rhythm, and controlling The finishing rolling speed, the straightening process improvement, and the reasonable rolling plan have realized the successful rolling of 7-10mm thin-gauge pipeline steel on the 4300mm wide and thick plate rolling mill. The process of the invention effectively solves the shape problem of thin-gauge pipeline steel plates, achieves higher rolling hit rate and yield rate, and can stably and mass-produce qualified products.

detailed description

Example 1

Select 1 piece of X65 pipeline steel, the thickness of the finished product is 8.8mm, and 10 pieces of 10mm thick steel plate have been rolled before rolling the target steel plate and the cooling water of the roller table is closed. The specific rolling process system of X65 is as follows:

(1) Dimensions of continuous casting slab: 150 thick * 1400 wide * 2700 long, rough plate size after rolling 8.8 thick * 2319 wide * 27665 long.

(2) The billet heating temperature is 1200°C, and the temperature of the upper and lower surfaces of the billet is 1213°C. The starting temperature of rough rolling is 1180°C, and the finishing temperature is 915°C.

(3) The total number of rolling passes is 14, the thickness of the intermediate billet is 50mm, and the number of finishing rolling is 7. The rolling procedures and parameters of the last 3 passes of the finishing rolling stage are shown in Table 1 below.

Table 1 The rolling schedule and parameters of the last three passes of finish rolling

(4) The steel throwing distance before the finishing mill is 1.9m, and the steel throwing distance after the mill is 3.4m.

(5) The opening amount of the cooling water in the middle of the roll body is adjusted to 80%, and that on both sides is adjusted to 50%.

(6) Turn off the cooling water of the roller table before and after the straightening, and raise the inlet guide roller of the straightening machine by 1.5mm.

Example 2

Select 1 piece of X65 pipeline steel, the thickness of the finished product is 10mm, and 12 pieces of 11.5mm thick steel plates have been rolled before rolling the target steel plate and the cooling water of the roller table is closed. The specific rolling process system of X65 is as follows:

(7) Continuous casting slab size: 180 thick * 1800 wide * 3180 long, the rough plate size after rolling is 10 thick * 2626 wide * 38501 long.

(8) The billet heating temperature is 1205°C, and the upper and lower surface temperatures of the billet are 1213°C and 1210°C respectively. The starting temperature of rough rolling is 1170°C, and the finishing temperature is 870°C.

(9) The total number of rolling passes is 12, the thickness of the intermediate billet is 40 mm, and the number of finishing rolling passes is 6. The rolling procedures and parameters of the last 3 passes of the finishing rolling stage are shown in Table 2 below.

Table 2 The rolling schedule and parameters of the last three passes of finish rolling

(10) The steel throwing distance before the finishing mill is 1.8m, and the steel throwing distance after the machine is 3.3m.

(11) The opening amount of cooling water in the middle of the roll body is adjusted to 70%, and that on both sides is adjusted to 50%.

(12) Turn off the cooling water of the roller table before and after the straightening, and lift the leading roller at the entrance of the straightening machine by 1.4mm.

Claims (1)

1. A kind of rolling process of wide and thick plate rolling mill production limit specification pipeline steel, it is characterized in that, concrete steps and parameters are as follows: 1) The thickness of the steel plate continuous casting slab is 150-200mm, and the rolling length of the steel plate is ≤40m; 2) The billet heating temperature is 1200°C-1230°C, the temperature difference between the upper and lower surfaces of the billet is within 30°C, and the final rolling temperature is 860-920°C; 3) Arrange the rolling of the steel plate with the target thickness in the middle and late stages of the rolling period. Before rolling the steel plate with the target thickness, arrange 8 to 12 steel plates with similar specifications for rolling, and the model adaptive coefficient approaches the rolling of the target thickness. state; 4) Before rolling the target steel plate, the cooling water of the input and output roller tables of the rolling mill is turned off; the total rolling passes are 12 to 14 passes, and the thickness of the intermediate billet is set to 40 to 60 mm; 5) Before rolling the target thickness steel plate, adjust the opening amount of the cooling water in the middle of the work roll body to 70-80%, and adjust to 40-50% on both sides; 6) After the rough rolling, the intermediate billet quickly enters the finishing mill through the intermediate connecting roller table, and the rolling speed of the finishing rolling is 4-7m/s; 7) The last 3 passes of finish rolling are rolled using the principle of equal-proportional crown, the rolling force of the last 3 passes decreases step by step, and the reduction decreases step by step, and the reduction of the final pass is controlled at 1.1-1.6mm; 8) Turn off the cooling water of the front and rear rollers of the straightening machine, and lift the inlet guide roller by 1.4-1.6mm during straightening; The steel throwing distance before the finishing mill is 1.8-2m, and the steel throwing distance after the mill is 3.3-3.5m; the number of passes for finishing rolling shall not exceed 7.