A control method for improving the first-pass yield of the shape of pipeline steel plates

Abstract

The present invention discloses a control method for improving the first-pass qualification rate of the shape of pipeline steel plates, which relates to the technical field of iron and steel production. The slab is lifted by the overhead crane to the stacking table, and then the pusher pushes the slab onto the roller table and finally loads it into the heating furnace; the furnace temperatures in the second heating section and the soaking section are carried out according to requirements; after the slab meets the heating system, the steelmaker taps the steel. The slab is descaled once by the descaling box. If it is not completely descaled, it is descaled again. If it is still not completely descaled, it is sent back to the furnace for treatment; in the rolling stage of the roughing mill, it must meet the requirement of descaling three times by the roughing mill; the intermediate slab is not skewed and is quickly sent to the front of the finishing mill, and descaling is carried out twice in the finishing stage; pre-straightening is carried out with large tilting and large reduction; the ultra-fast cooling process: different cooling processes are adopted for different grades of pipeline steel; for the X42 grade, straightening is carried out with a small reduction, and for the X50-X70 grades, straightening is carried out with a large reduction; the finishing workshop empties the cooling bed in advance. After the steel plate is segmented, it is quickly taken off the production line for shearing.

Description

Technical Field

[0001] The present invention relates to the technical field of steel production, and particularly to a control method for improving the first-pass qualification rate of the shape of pipeline steel plates. Background Art

[0002] Ferrite-pearlite pipeline steels generally include grades X42-X70. Due to their characteristics such as high strength, high impact toughness, and good welding performance, they are widely used in industrial projects such as pipeline transportation of petroleum, natural gas, etc. Because pipeline steels have excellent mechanical properties, during production, usually due to their relatively low return red temperature, there are large internal stresses in the steel plates during the cooling process. If the internal stresses cannot be released, the shape of the steel plates is usually poor, making it difficult to roll during the rolling process. After cooling and straightening, there will also be secondary deformation in the shape, affecting the first-pass qualification rate of the shape. The warped plates must go through processes such as flattening and straightening to meet the usage requirements of customers. This not only increases the production cost on the one hand, but also affects the contract delivery on the other hand, causing customer complaints.

[0003] Therefore, in order to solve the shape problems of pipeline steel plates of grades X42-X70, it is urgent to optimize the processes in heating, rolling, cooling, straightening, etc., and it is also necessary to apply control means after the steel plates are taken off the production line to improve the first-pass qualification rate of the shape of pipeline steel plates. Summary of the Invention

[0004] In view of the above technical problems, the present invention overcomes the shortcomings of the prior art and provides a control method for improving the first-pass qualification rate of the shape of pipeline steel plates, including the following steps:

[0005] After the slab is stored in the warehouse, the surface quality of the billet is inspected, the cutting slag burrs are cleaned, and it is lifted to the stacking table by the overhead crane. Subsequently, the pusher pushes the slab onto the roller table and finally loads it into the heating furnace;

[0006] The fireman controls the temperature of each section according to the heating system, and the furnace temperatures of the second heating section and the soaking section are in accordance with the requirements;

[0007] After the slab meets the heating system, the steelmaker taps the steel. The slab is descaled once by the descaling box. If it is not completely descaled, it is descaled again. If it is still not completely descaled, it is sent back to the furnace for treatment;

[0008] During the rolling stage of the roughing mill, it must meet the requirement of three descaling operations by the roughing mill;

[0009] The intermediate billet is not stacked, and is quickly fed to the front of the finishing mill. Two descaling operations are carried out during the finishing stage;

[0010] Pre-straightening is carried out with large tilting and large reduction amounts;

[0011] Ultra-fast cooling process: Different cooling processes are adopted for different grades of pipeline steels;

[0012] The X42 grade is straightened with a small reduction, and the X50-X70 grades are straightened with a large reduction;

[0013] The finishing workshop empties the cooling bed in advance. After the steel plate is segmented, it is quickly taken offline for shearing.

[0014] The further limited technical solution of the present invention is:

[0015] For the control method for improving the first-pass qualification rate of the shape of pipeline steel plates described above, the furnace temperatures of the second heating section and the soaking section are carried out at 1200-1220 °C.

[0016] For the control method for improving the first-pass qualification rate of the shape of pipeline steel plates described above, the rough rolling mill rolls 11 passes. High-pressure descaling is carried out in the first pass, the third pass and the fifth pass, and it is necessary to meet the requirement of three descaling passes for the rough rolling mill.

[0017] For the control method for improving the first-pass qualification rate of the shape of pipeline steel plates described above, the finishing rolling mill rolls 5 passes. Descaling is carried out in the first pass and the fourth pass, and there are two descaling passes in the finishing rolling stage.

[0018] For the control method for improving the first-pass qualification rate of the shape of pipeline steel plates described above, the pre-straightening process is: load reduction is 1.5-1.7 mm, tilting correction is 1.0-1.6 mm, and roll gap correction is -0.4 to -0.8 mm.

[0019] For the control method for improving the first-pass qualification rate of the shape of pipeline steel plates described above, the ultra-fast cooling process: for the X42 grade, the 3rd and 5th groups of headers, the flow rate is 170 m 3 / h, the water ratio is 1.30-1.40, the speed is 0.9-1.0 m / s, and the acceleration is 0.008-0.01 m / s 2 ; for the X52-X70 grades, the 3rd to 10th groups of headers, the flow rate is 180, the water ratio is 1.30-1.40 m 3 / h, the speed is 0.85-0.9 m / s, and the acceleration is 0.003-0.005 m / s 2 .

[0020] For the control method for improving the first-pass qualification rate of the shape of pipeline steel plates described above, the precision straightening process is: the straightening force for the X42 grade is 1200 tons, and the straightening force for the X52-X70 grades is 1650 tons.

[0021] The beneficial effects of the present invention are:

[0022] (1) The heating process formulated by the present invention is heated at medium and low temperatures, which can effectively reduce the unit consumption of the heating furnace;

[0023] (2) The rolling process formulated by the present invention can ensure the normal arrangement of the rolling schedule, which not only ensures rolling with a large reduction, but also ensures a smooth rhythm in the rolling stage;

[0024] (3) The cooling and straightening processes formulated in the present invention not only ensure that the performance meets the requirements, but also ensure that the straightened steel plate is flat.

[0025] (4) The rapid offline method of the steel plate adopted in the present invention can effectively eliminate the internal stress of the steel plate, and the straightness of the steel plate after shearing is better. Specific implementation mode

[0026] Example 1

[0027] A control method for improving the first-pass qualification rate of the shape of pipeline steel plates provided in this example, the rolling information is X52 of 12.7 * 2490 mm, and the specific implementation is as follows:

[0028] After the slab is put into storage, the surface quality of the blank is inspected, the cutting slag burrs are cleaned, and it is lifted to the stacking table by a crane, and then the pusher pushes the slab onto the roller table and finally loads it into the heating furnace;

[0029] The fireman controls the temperature of each section according to the heating system. The heating temperature of the second heating section is 1213 °C, and the soaking section temperature is 1207 °C;

[0030] After the slab meets the heating system, the steelmaker taps the steel. The slab is descaled once by the descaling box and sent to the front of the rough rolling mill;

[0031] The rough rolling mill rolls 11 passes, and high-pressure descaling is carried out in the first pass, the third pass and the fifth pass;

[0032] After rolling, the intermediate billet of the rough rolling mill is not swung, and the steel is quickly sent to the front of the finishing rolling mill. The finishing rolling mill rolls 5 passes, and descaling is carried out in the first pass and the fourth pass;

[0033] The pre-straightening process is: the load is reduced by 1.5 mm, the tilt is corrected by 1.0 mm, and the roll gap is corrected by -0.8 mm;

[0034] Ultra-fast cooling process: Open the 3rd - 10th groups of headers, the flow rate is 180 m 3 / h, the water ratio is 1.40, the speed is 0.9 m / s, and the acceleration is 0.005 m / s 2 ;

[0035] The finishing straightening process is: the straightening force is 1642 tons;

[0036] The finishing workshop empties the cooling bed in advance. After the steel plate is segmented, it is quickly taken offline for shearing.

[0037] The steel plate produced according to this method has good straightness and is stored as a genuine product.

[0038] Example 2

[0039] A control method for improving the first-pass qualification rate of pipeline steel plate shape provided in this embodiment, with the rolling information being X42 of 12*1868mm, and the specific implementation is as follows:

[0040] After the slab is put into storage, the surface quality of the billet is inspected, the cutting slag burrs are cleaned, and it is lifted to the stacking table by the overhead crane. Subsequently, the pusher pushes the slab onto the roller table and finally loads it into the heating furnace;

[0041] The fireman controls the temperature of each section according to the heating system. The heating temperature in the second heating section is 1208°C, and the soaking section temperature is 1218°C;

[0042] After the slab meets the heating system, the steelmaker taps the steel. The slab is descaled once by the descaling box and sent to the front of the roughing mill;

[0043] The roughing mill rolls 11 passes, and high-pressure descaling is carried out in the first pass, the third pass, and the fifth pass;

[0044] After rolling, the intermediate billet of the roughing mill is not turned, and it is quickly sent to the front of the finishing mill. The finishing mill rolls 5 passes, and descaling is carried out in the first pass and the fourth pass;

[0045] The pre-straightening process is as follows: the load is reduced by 1.7mm, the tilt correction is 1.6mm, and the roll gap correction is -0.4mm;

[0046] Ultra-fast cooling process: Open the 3rd and 5th groups of headers, with a flow rate of 170 m 3 / h, a water ratio of 1.30, a speed of 1.0m / s, and an acceleration of 0.01m / s 2 ;

[0047] The finishing straightening process is as follows: the straightening force is 1212 tons;

[0048] The finishing workshop empties the cooling bed in advance. After the steel plate is segmented, it is quickly taken off the line for shearing.

[0049] The steel plate produced according to this method has good flatness and is put into storage as a genuine product.

[0050] In May 2022, 3279 tons of pipeline steel were rolled, with 564 tons of warping. The warping incidence rate was 17.2%. The cold straightening and flattening cost for the warped steel plate was 180 yuan / ton. The warping incidence rate of the pipeline steel decreased from 17.2% to 7.73% at the present stage. Therefore, the annual cost savings was approximately 3279×12×(17.2% - 6.73%)×180 = 741,600 yuan.

[0051] In addition to the above embodiments, the present invention may also have other implementation manners. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention.

Claims

1. A control method for improving the first-pass yield of the shape of pipeline steel plates, characterized in that: It includes the following steps: After the slab is stored in the warehouse, the surface quality of the billet is inspected, the cutting slag and burrs are cleaned, and it is lifted to the stacking table by the overhead crane. Subsequently, the pusher pushes the slab onto the roller table and finally loads it into the heating furnace; The fireman controls the temperature of each section according to the heating system, and the furnace temperature of the second heating section and the soaking section meets the requirements; After the slab meets the heating system, the steelmaker taps the steel. The slab is descaled once by the descaling box. If it is not completely descaled, it is descaled again. If it is still not completely descaled, it is sent back to the furnace for treatment; During the rolling stage of the roughing mill, three descaling operations of the roughing mill must be satisfied; The intermediate billet is not stacked, and is quickly fed to the front of the finishing mill. Two descaling operations are carried out in the finishing stage; Pre-straightening is carried out with large tilting and large reduction. The pre-straightening process is: the reduction under load is 1.5 - 1.7 mm, the tilting correction is 1.0 - 1.6 mm, and the roll gap correction is -0.4 - 0.8 mm; Ultra-fast cooling process: Different cooling processes are adopted for pipeline steels of different grades; For the X42 grade, small reduction is used for finishing straightening, and for the X52 - X70 grades, large reduction is used for finishing straightening. The finishing straightening process is: the straightening force for the X42 grade is 1200 tons, and the straightening force for the X52 - X70 grades is 1650 tons; The finishing workshop empties the cooling bed in advance. After the steel plate is segmented, it is quickly taken offline for shearing.

2. The control method for improving the first-pass qualification rate of the shape of pipeline steel plates according to claim 1, wherein: The furnace temperature of the second heating section and the soaking section is 1200 - 1220 °C.

3. A control method for improving the first-pass rate of the shape of pipeline steel plates according to claim 1, characterized in that: The roughing mill rolls 11 passes. High-pressure descaling is carried out in the first pass, the third pass and the fifth pass. Three descaling operations of the roughing mill must be satisfied.

4. A control method for improving the first-pass qualification rate of the shape of pipeline steel plates according to claim 1, characterized in that: The finishing mill rolls 5 passes. Descaling is carried out in the first pass and the fourth pass. Two descaling operations are carried out in the finishing stage.

5. A control method for improving the first-pass rate of the shape of pipeline steel plates according to claim 1, characterized in that: Ultra-fast cooling process: Grade X42, header groups 3 and 5, flow rate 170 m 3 / h, water ratio 1.30 - 1.40, speed 0.9 - 1.0 m / s, acceleration 0.008 - 0.01 m / s 2 ; For grades X52 - X70, header groups 3 - 10, flow rate 180 m 3 / h, water ratio 1.30 - 1.40, speed 0.85 - 0.9 m / s, acceleration 0.003 - 0.005 m / s 2 .