Rolling production method of steel for phi 13mm SWRH82B prestressed steel strand

Abstract

The invention provides a rolling production method of steel for a phi 13mm SWRH82B prestressed steel strand. The rolling production method is characterized by comprising the following steps: 1) taking a continuous casting billet as a raw material; (2) the continuous casting billet is sent to a heating furnace to be heated, discharged out of the furnace, descaled and rolled under the condition that the initial rolling temperature is 1010-1050 DEG C, and an SWRH82B prestressed steel strand wire rod with the diameter being 13 mm is obtained; (3) the SWRH82B prestressed steel strand wire rod with the diameter being 13 mm is fed into an air cooling roller way with the speed being 0.75-0.95 m / s and provided with a plurality of heat preservation covers and a plurality of draught fans, and slow cooling is conducted; 4, the slowly cooled SWRH82B prestressed steel strand wire rod with the diameter being 13 mm is bundled and subjected to stack cooling to the normal temperature, and the finished product of the SWRH82B prestressed steel strand wire rod with the diameter being 13 mm is obtained.The deep processing capacity of steel is improved, heat-preservation-free slow cooling of steel for prestressed steel strands is achieved, the production technological process is reduced, and energy conservation and consumption reduction are achieved.

Description

Technical Field

[0001] This invention belongs to the field of steel rolling production technology, and particularly relates to a rolling production method for prestressed steel strand. Background Technology

[0002] Prestressed steel strand is a new type of high-efficiency and energy-saving steel. Its tensile strength is more than twice that of hot-rolled steel bars, which can save steel consumption in reinforced concrete and reduce project costs by about 40%. It is currently widely used in large bridges, crane beams, railway sleepers, utility poles, and large-diameter high-pressure cement pipes. The existing main production process for prestressed steel strand is: billet heating → rolling → wire collection → heat preservation and slow cooling → bundling → uncoiling → stacking and cooling → finished product. The purpose of the heat preservation and slow cooling process is to release structural stress and internal stress, improve the mechanical properties of the steel, and ensure that the tensile strength and reduction of area of ​​the steel meet project requirements. However, with the increasing demands of the dual-carbon era and intensifying industry competition, the heat preservation and slow cooling process, due to its high requirements for ambient temperature and long heat preservation time, has become a factor affecting production efficiency and even hindering cost reduction and efficiency improvement. Therefore, it is necessary to improve the existing technology. Summary of the Invention

[0003] To overcome the above-mentioned shortcomings of the existing technology, the present invention provides a rolling production method for Φ13mmSWRH82B prestressed steel strand.

[0004] This invention is achieved through the following technical solution: a rolling production method for Φ13mm SWRH82B prestressed steel strand, characterized by comprising the following steps: 1) The continuously cast billet with the following chemical composition by mass percentage is used as raw material: C: 0.80~0.85%, Si: 0.15~0.30%, Mn: 0.75~0.90%, Cr: 0.200~0.245%, P≤0.020%, S≤0.015%, As≤0.042%, V: 0.032~0.048%, with the remainder being Fe and unavoidable impurities; 2) The continuously cast billet from step 1) is heated in a furnace, removed from the furnace, descaled, and then fed into a roughing mill for six passes at an initial rolling temperature of 1010–1050℃. It is then fed into an intermediate rolling mill for six passes, followed by a pre-finishing mill with six stands for four passes. The last two stands of the pre-finishing mill are skipped. Afterward, two passes of finishing rolling are performed at a finishing temperature of 880–955℃. After skipping six stands, the billet is then... At a temperature of 860–950℃, the wire enters the sizing mill for rolling. This sizing mill is a 1+1+2 stand sizing mill, which is a twist-free modular mill with a top cross-section of 45°. Each of the first two stands is driven by a motor and an external speed increaser with multiple speed ratios, while the last two stands are driven by a single motor. Finally, the wire is spun and collected at a temperature of 855–935℃ to obtain Φ13mm SWRH82B prestressed steel strand wire rod. 3) Feed the Φ13mmSWRH82B prestressed steel strand from step 2) into an air-cooled roller conveyor with a speed of 0.75~0.95m / s and equipped with several insulation covers and several fans, and perform the following slow cooling: Open several insulation covers at the front section of the air-cooled roller conveyor and close several insulation covers at the rear section of the air-cooled roller conveyor. Check the coil temperature at the outlet of the last fan in a timely manner, so that the temperature at the overlap point of the fan outlet is ≤600℃; when the temperature at the overlap point of the fan outlet is >600℃, check and confirm whether the fan operation and cooling are normal. If there is any abnormality in the fan, adjust the fan in time. When the fan operation and cooling are normal, reduce the wire feeding temperature by 10~20℃, so that the temperature at the non-overlap point in the middle of the Φ13mmSWRH82B prestressed steel strand coil is ≤600℃. 4) After the Φ13mmSWRH82B prestressed steel strand coils in step 3) are slowly cooled, they are bundled and stacked to cool to room temperature to obtain the finished Φ13mmSWRH82B prestressed steel strand coils.

[0005] The descaling in step 2) is a conventional high-pressure water descaling process.

[0006] After roughing on the roughing mill, intermediate rolling on the intermediate mill, pre-finishing rolling, and finishing rolling on the finishing mill in step 2), the head and tail are cut off using a flying shear and a hydraulic shear, respectively.

[0007] After the pre-finishing rolling and the finishing rolling of the finishing mill in step 2), water spray cooling control is set up to control the temperature of the rolled piece.

[0008] Compared with the prior art, the present invention has the following advantages and effects: By optimizing the chemical composition of the billet, precisely controlling the rolling process, and controlling the temperature cooling after rolling, the problems of low plasticity, high environmental temperature requirements, long heat preservation time, low production efficiency, and poor energy saving and consumption reduction effects of steel used in prestressed steel strands after rolling are effectively solved due to internal stress concentration. This improves the deep processing capability of steel, enables heat preservation-free slow cooling of steel used in prestressed steel strands, reduces the production process, and achieves energy saving and consumption reduction. Detailed Implementation

[0009] The present invention will be further described below through embodiments. Example 1

[0010] A rolling production method for Φ13mm SWRH82B prestressed steel strand, characterized by comprising the following steps: 1) The raw material is a continuously cast billet with the following chemical composition by mass percentage and a size of 165mm×165mm: C: 0.83%, Si: 0.22%, Mn: 0.80%, Cr: 0.223%, P: 0.013%, S: 0.012%, V: 0.035%, As: 0.017%, with the remainder being Fe and unavoidable impurities; 2) The continuously cast billet from step 1) is heated in a furnace to the initial rolling temperature of 1025–1038℃, removed from the furnace, descaled with high-pressure water, and then sent to the roughing mill for six passes of roughing rolling. A flying shear is used to cut off the head and tail of the rolled piece, resulting in a size of 77mm × 77.07mm and an elongation coefficient of 1.341. It is then sent to the intermediate mill for six passes of intermediate rolling, with the flying shear again cutting off the head and tail. The resulting size is 33mm × 33.07mm and an elongation coefficient of 1.319. Finally, it undergoes four passes of pre-finishing rolling, water cooling, and another flying shear cuts off the head and tail. After two empty passes, the final size is 20mm. The length of the prestressed steel strand is 16.8mm × 20.5mm with an elongation of 1.484. It is then rolled in the finishing mill at 897–926℃, followed by two more finishing passes, and then water-cooled after six passes. The resulting strand has a length of 16.8mm × 16.8mm and an elongation of 1.259. Next, it undergoes four passes of reducing sizing rolling at 896–912℃, resulting in a strand size of 13.15mm × 13.15mm with an elongation of 1.000. After further water cooling, it is finally coiled and collected at 886–912℃ to obtain Φ13mm SWRH82B prestressed steel strand. 3) Feed the Φ13mmSWRH82B prestressed steel strand from step 2) into an air-cooled roller conveyor with a speed of 0.75m / s and equipped with insulation covers 1#-22# and fans 1#-10#, and perform the following slow cooling: open insulation covers 1#-12# at the front of the air-cooled roller conveyor, close insulation covers 13#-22# at the rear of the air-cooled roller conveyor, and check the outlet temperature of the last fan 10# in a timely manner. The temperature at the overlap point of the fan outlet is 570~580℃, and the temperature at the non-overlap point in the middle of the strand is 540~550℃. 4) After the Φ13mmSWRH82B prestressed steel strand coils in step 3) are slowly cooled, they are bundled and stacked to cool to room temperature to obtain the finished Φ13mmSWRH82B prestressed steel strand coils.

[0011] Mechanical testing revealed that the tensile strength of the Φ13mm SWRH82B prestressed steel strand was 1200MPa, and the reduction of area was 36%. The product inspection results meet the delivery technical conditions. Example 2

[0012] A rolling production method for Φ13mm SWRH82B prestressed steel strand, characterized by comprising the following steps: 1) The raw material is a continuously cast billet with the following chemical composition by mass percentage and a specification of 165mm×165mm: C: 0.84%, Si: 0.21%, Mn: 0.82%, Cr: 0.214%, P: 0.009%, S: 0.014%, V: 0.035%, As: 0.013%, with the remainder being Fe and unavoidable impurities; 2) The continuously cast billet from step 1) is heated in a heating furnace to the initial rolling temperature of 1025-1038℃, removed from the furnace, descaled with high-pressure water, and then sent to the roughing mill for six passes of roughing rolling. A flying shear is used to cut off the head and tail of the rolled piece, which has a size of 77mm × 77.07mm and an elongation coefficient of 1.341. It is then sent to the intermediate mill for six passes of intermediate rolling, with the flying shear again cutting off the head and tail. The rolled piece has a size of 33mm × 33.07mm and an elongation coefficient of 1.319. Finally, it undergoes four passes of pre-finishing rolling, water cooling, and the flying shear again cutting off the head and tail. After two empty passes, the rolled piece has a size of 20. The length of the prestressed steel strand is 16.8mm × 16.8mm with an elongation of 1.484. It is then rolled in two passes at a finishing temperature of 897–926℃, followed by six passes of water cooling. The resulting strand has an elongation of 1.259. Next, it undergoes four passes of reduction sizing rolling at 896–912℃, producing a strand with an elongation of 13.15mm × 13.15mm and an elongation of 1.000. After further water cooling, the strand is finally produced and collected at 886–912℃ to obtain Φ13mm SWRH82B prestressed steel strand. 3) Feed the Φ13mmSWRH82B prestressed steel strand from step 2) into an air-cooled roller conveyor with a speed of 0.80m / s and equipped with insulation covers 1#-22# and fans 1#-10#, and perform the following slow cooling: open insulation covers 1#-12# at the front of the air-cooled roller conveyor, close insulation covers 13#-22# at the rear of the air-cooled roller conveyor, and check the outlet temperature of the last fan 10# in a timely manner. The outlet overlap temperature of the fan is 575~585℃, and the temperature at the non-overlapping point in the middle of the strand is 545~555℃. 4) After the Φ13mmSWRH82B prestressed steel strand coils in step 3) are slowly cooled, they are bundled and stacked to cool to room temperature to obtain the finished Φ13mmSWRH82B prestressed steel strand coils.

[0013] Mechanical testing revealed that the tensile strength of the Φ13mm SWRH82B prestressed steel strand was 1220MPa, and the reduction of area was 38%. The product inspection results meet the delivery technical conditions.

[0014] in conclusion: (1) Compared with the conventional production process of prestressed steel strand steel in high-speed wire rod mill, the present invention does not require heat preservation and slow cooling after coiling, and can realize the rolling production of prestressed steel strand steel. The rolling process is simple, the accident rate is low, and the production efficiency is improved. (2) This invention achieves post-rolling heat preservation slow cooling treatment of prestressed steel strand by optimizing the composition range of the billet, controlling the material shape, rolling temperature, transport speed, and controlling the cooling with a heat preservation cover. (3) This invention mainly utilizes the residual heat of the steel itself and the heat preservation and cooling of the air-cooled roller conveyor to achieve the post-rolling heat treatment of steel for prestressed steel strands. The steel has the characteristics of being economical and environmentally friendly in the production process.

[0015] In summary, this invention effectively solves the problems of low plasticity, high environmental temperature requirements, long heat preservation time, low production efficiency, and poor energy saving and consumption reduction effects of prestressed steel strands due to internal stress concentration after rolling. It improves the deep processing capability of steel, realizes heat preservation-free slow cooling of prestressed steel strands, reduces production process steps, and achieves energy saving and consumption reduction.

Claims

1. A rolling production method for Φ13mm SWRH82B prestressed steel strand, characterized in that... Includes the following steps: 1) The continuously cast billet with the following chemical composition by mass percentage is used as raw material: C: 0.80~0.85%, Si: 0.15~0.30%, Mn: 0.75~0.90%, Cr: 0.200~0.245%, P≤0.020%, S≤0.015%, As≤0.042%, V: 0.032~0.048%, with the remainder being Fe and unavoidable impurities; 2) The continuously cast billet from step 1) is heated in a furnace, removed from the furnace, descaled, and then fed into a roughing mill for six passes at an initial rolling temperature of 1010–1050℃. It is then fed into an intermediate rolling mill for six passes, followed by a pre-finishing mill with six stands for four passes. The last two stands of the pre-finishing mill are skipped. Afterward, two passes of finishing rolling are performed at a finishing temperature of 880–955℃. After skipping six stands, the billet is then... At a temperature of 860–950℃, the wire enters the sizing mill for rolling. This sizing mill is a 1+1+2 stand sizing mill, which is a twist-free modular mill with a top cross-section of 45°. Each of the first two stands is driven by a motor and an external speed increaser with multiple speed ratios, while the last two stands are driven by a single motor. Finally, the wire is spun and collected at a temperature of 855–935℃ to obtain Φ13mm SWRH82B prestressed steel strand wire rod. 3) Feed the Φ13mmSWRH82B prestressed steel strand from step 2) into an air-cooled roller conveyor with a speed of 0.75~0.95m / s and equipped with several insulation covers and several fans, and perform the following slow cooling: Open several insulation covers at the front section of the air-cooled roller conveyor and close several insulation covers at the rear section of the air-cooled roller conveyor. Check the coil temperature at the outlet of the last fan in a timely manner, so that the temperature at the overlap point of the fan outlet is ≤600℃; when the temperature at the overlap point of the fan outlet is >600℃, check and confirm whether the fan operation and cooling are normal. If there is any abnormality in the fan, adjust the fan in time. When the fan operation and cooling are normal, reduce the wire feeding temperature by 10~20℃, so that the temperature at the non-overlap point in the middle of the Φ13mmSWRH82B prestressed steel strand coil is ≤600℃. 4) After the Φ13mmSWRH82B prestressed steel strand coils in step 3) are slowly cooled, they are bundled and stacked to cool to room temperature to obtain the finished Φ13mmSWRH82B prestressed steel strand coils.

2. The rolling production method for Φ13mm SWRH82B prestressed steel strand according to claim 1, characterized in that... The descaling in step 2) is a conventional high-pressure water descaling process.

3. The rolling production method for Φ13mm SWRH82B prestressed steel strand according to claim 1, characterized in that... After roughing on the roughing mill, intermediate rolling on the intermediate mill, pre-finishing rolling, and finishing rolling on the finishing mill in step 2), the head and tail are cut off using a flying shear and a hydraulic shear, respectively.

4. The rolling production method for Φ13mm SWRH82B prestressed steel strand according to claim 1, characterized in that... After the pre-finishing rolling and the finishing rolling of the finishing mill in step 2), water spray cooling control is set up to control the temperature of the rolled piece.