Production method of extra-thick building structure steel plate with small compression ratio and high Z-direction performance

Abstract

The invention relates to the technical field of steel processing, and discloses a production method of a small-compression-ratio high-Z-direction-performance extra-thick building structure steel plate, which comprises the following steps: carrying out LF refining smelting treatment on molten steel; heating treatment; performing differential temperature control on the plate blank and the intermediate blank; performing controlled rolling and controlled cooling treatment; carrying out heap cold treatment after rolling; according to the production method of the extra-thick building structure steel plate with the small compression ratio and the high Z-direction performance, the controlled rolling and controlled cooling process is adopted, the complex tempering / normalizing / tempering heat treatment procedure does not need to be carried out, precious alloys such as Ni, Mo and Cu do not need to be added, the production process path can be greatly simplified, the cost is reduced, and the delivery cycle is shortened; under the condition that the compression ratio is smaller than or equal to 3, continuous casting billets with the fracture surface of 300 mm, which are possessed by mainstream steel mills, replace large-fracture-surface casting billets / mold ingots to roll the extra-thick plate with the maximum thickness of 120 mm, extra equipment investment is avoided, and cost reduction, efficiency improvement and quality improvement are achieved at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of steel material processing, in particular to a method for producing a special thick building structure steel plate with a small compression ratio and high Z-direction performance. Background Art

[0002] Construction steel refers to steel widely used in steel structures such as super high-rise buildings, stations, airports, and exhibition centers. Construction steel has the characteristics of fast construction speed, good earthquake resistance, and environmental friendliness. Q460GJ grade building structure steel has been widely used in various major projects. It can effectively reduce the deadweight of steel structures and provide higher structural strength.

[0003] Chinese patent CN110616377A proposes a Q460GJ production steel plate with low yield ratio and high toughness, but the applicable thickness of the steel plate is ≤80mm, and the process will have low strength at the 1 / 4 position when producing a thickness of more than 100mm, which cannot meet the requirements of the Q460GJ steel grade, and there is also instability in thick-drawn Z35. Chinese patent CN111748678A proposes a low compression ratio, large thickness, lamellar tear resistant steel plate and its manufacturing method, which does not undergo special pressure processing. After the two stages of rough and fine rolling, the semi-finished product needs to be slowly cooled and then heat-treated to achieve the desired result. The process cost is high, the process flow is long, and the production thickness range is 60-90mm, which is not suitable for the production of thickness specifications above 100mm. Chinese patent CN115216701A proposes a low compression ratio, lamellar tear resistant Q960 high-strength steel and its preparation method, which does not undergo special pressure processing. After rolling, it needs to be tempered and heat-treated. The alloy cost is high and it is only suitable for the production of high-strength steel. Chinese patent CN105925894A proposes an ultra-thick, high-strength, lamellar tear resistant Q500D-Z35 hydropower unit steel plate and its manufacturing method. It is rolled from steel ingots and requires quenching and tempering heat treatment after rolling. It has not undergone special pressure processing methods and is not suitable for low-cost production of high-rise structural steel. Chinese patent CN101987330A proposes an ultra-thick, lamellar tear resistant steel plate manufacturing method. It adopts a die-cast ingot forging production method. The steel plate requires normalizing heat treatment, which has high production costs and is not conducive to promotion on steel plates with thickness ranges of 100-120mm. Chinese patent CN108914005B proposes an ultra-thick, corrosion-resistant steel plate with excellent low-temperature toughness and a yield strength of >460MPa and its production method. This method uses high alloy components, and its main alloys are Mn: 2.02-2.35%, Nb: 0.041-0.062%, V: 0.121-0.162%, Ti: 0.022-0.051%, Cu: 0.76-1.02%, Ni: 0.77-1.08%. The alloy cost is extremely high, and normalizing heat treatment is required after rolling, which cannot guarantee economic efficiency and is not suitable for promotion on 100-120mm high-building structure steel. Chinese patent CN114480969A proposes a production method for Q460GJ, a super thick steel with high toughness and high Z-direction performance with a compression ratio of ≤4, which is suitable for production of 80-100mm thickness. Its chemical composition: C: 0.1~0.13, Si: 0.1~0.3, Mn: 1.1~1.3, P≤0.012, S≤0.003, Cr: 0.3~0.5, Ti: 0.01~0.02, Nb: 0.01~0.02, Ni: 0.1~0.3, V: 0.06~0.07, Als: 0.025~0.035, etc. and the cooling temperature after rolling is 530~550℃. This composition and process are not suitable for expanding the production of thickness above 100mm.Because as the thickness increases, the cooling rate must be further increased to improve the strength in the plate, and its carbon content is 0.1~0.13. When the cooling rate is further increased, the surface hard phase structure ratio will further increase, which will further deteriorate the surface toughness and cause the yield ratio to rise, resulting in a large performance difference in the full thickness direction, which cannot meet the steel grade requirements. Chinese patent CN105525209B proposes a low yield ratio Q460GJ construction steel and its production method. This method is suitable for production of limited thickness (the upper limit thickness of the example is 50mm), using a C content of 0.17-0.19%, and a final cooling temperature of 660-680℃. It is impossible to produce Q460GJ above 100mm.

[0004] In view of this, we proposed a production method for extra-thick building structural steel plates with small compression ratio and high Z-direction performance. Summary of the invention

[0005] The object of the present invention is to provide a method for producing a particularly thick building structural steel plate with a small compression ratio and high Z-direction performance, so as to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for producing a thick building structure steel plate with a small compression ratio and high Z-direction performance, comprising the following steps: S1, molten steel is treated by LF refining and smelting; S2, heating treatment; S3, temperature difference control between slab and intermediate billet; S4, controlled rolling and controlled cooling treatment; S5, cold treatment after rolling; S6. Finished product storage processing.

[0007] Optionally, S1 includes: the molten steel is refined by LF, vacuum treated by RH / VD, the S content is strictly controlled during smelting, and then protected and cast into a 300mm thick continuous casting billet, the low-power judgment of the billet reaches ≤ national standard C class 1.5, and 200m of calcium wire is fed to each furnace.

[0008] Optionally, S2 further includes: the total slab heating time is ≥280 min, the soaking temperature is 1170~1260°C, the soaking time is ≥40 min, and the core temperature of the cast slab is 1170~1260°C.

[0009] Optionally, S3 further includes: using a rough descaling box to extend the water pumping time, descaling the rough rolling mill with descaling water in each pass, and using the collecting pipes of the intermediate rollers of the rough rolling and finishing mills to water-cool the upper and lower surfaces of the slab. After water pumping, the thickness of the sandwich layer on the upper and lower surfaces is greater than 20 mm, the difference between the surface and the core of the intermediate slab is greater than 100°C, and the difference between the surface red-return temperature of the intermediate slab at the start of finishing rolling and the core temperature is greater than 50°C, so that greater plastic deformation and stress are introduced into the center of the steel plate during the rolling process.

[0010] Optionally, the total time of the water pumping time is greater than 15 seconds.

[0011] Optionally, S4 includes: adopting two-stage controlled rolling, during the rough rolling process with a rolling temperature ≥1140°C, at least one pass has a reduction rate ≥18%, the rough rolling end temperature is controlled to be 1130~1180°C and the reduction rate of this pass is ≥16%; the intermediate billet thickness is ≥ the finished product thickness + 40mm, and the finishing temperature of fine rolling is 780~820°C; after rolling, it is directly put into water and cooled to the target temperature at a cooling rate of 3~6°C / s through a MULPIC device, and then air-cooled on a cooling bed through hot straightening.

[0012] Optionally, S5 further comprises: air cooling the cooling bed to a surface temperature of 300-350°C, placing the cooling bed in a heat preservation pit for stack cooling, wherein the stack cooling time is greater than 60 hours, and the surface temperature is less than 90°C, and the stack is removed without heat treatment, and fire cutting to length is directly performed.

[0013] Compared with the prior art, the present invention provides a method for producing a particularly thick building structural steel plate with a small compression ratio and high Z-direction performance, which has the following beneficial effects: 1. The production method of the small compression ratio high Z-direction performance extra-thick building structure steel plate adopts controlled rolling and controlled cooling (process, which does not require complex quenching / normalizing / tempering heat treatment procedures, and does not require the addition of precious Ni, Mo, Cu and other alloys, which can greatly simplify the production process path, reduce costs and shorten delivery cycles; when the compression ratio is ≤3, the 300mm section continuous casting billet that mainstream steel mills have can replace the large section casting billet / mold casting ingot to roll the maximum thickness of 120mm extra-thick plate, avoiding additional equipment investment, and achieving cost reduction, efficiency improvement and quality improvement.

[0014] 2. The production method of the extra-thick building structure steel plate with small compression ratio and high Z-direction performance adopts the differential temperature rolling method, which can be realized by using the intermediate water cooling device of the basic equipment of the medium and thick plate production line. It can stably produce extra-thick Q460GJDZ35 steel plates with a maximum thickness of 120mm, and the performance fully meets the requirements of the national standard GBT19879-2023.

[0015] 3. Compared with the conventional production method, the production method of the small compression ratio high Z-direction performance extra-thick building structure steel plate can significantly improve the Z35 qualified rate and ZL mean value by adopting the present invention. The Z35 qualified rate of 100-120mm thickness can be stabilized to more than 98%, and the mean value can be stabilized to more than 45%; the use of 350mm cross-section continuous casting billets can be expanded, and TMCP rolling can be used to produce 120-140mm thickness; the maximum thickness of the 260mm continuous casting billet section can be produced to 95mm, and the grades cover Q345GJ~Q460GJ, which has good scalability. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present invention will be described clearly and completely below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The present invention provides a technical solution: a method for producing a particularly thick building structural steel plate with a small compression ratio and high Z-direction performance, comprising the following steps: S1. The molten steel is smelted by LF refining; the molten steel is LF refined, RH / VD vacuum treated, the S content is strictly controlled during smelting, and then protected and cast into 300mm thick continuous casting billets. The low-power judgment of the billet reaches ≤ national standard C class 1.5, and 200m of calcium wire is fed to each furnace.

[0018] S2. Heating treatment: the total heating time of the slab is ≥280min, the soaking temperature is 1170~1260℃, the soaking time is ≥40min, and the core temperature of the cast steel is 1170~1260℃.

[0019] S3, temperature difference control between slab and intermediate slab; use rough descaling box to extend water pumping time, descaling water is used for each pass on rough rolling mill, and water cooling is performed on the upper and lower surfaces of slab by using the header of the intermediate roller table of rough rolling mill and finishing mill. After water pumping, the thickness of the sandwich layer on the upper and lower surfaces is greater than 20mm, the temperature difference between the surface and the center of the intermediate slab is greater than 100℃, and the temperature difference between the red-returning temperature of the intermediate slab surface and the center of the finishing rolling is greater than 50℃, so that greater plastic deformation and stress are introduced into the center of the steel plate during rolling. The total time of the water pumping time is greater than 15s.

[0020] S4, controlled rolling and controlled cooling treatment; adopt two-stage controlled rolling, during the rough rolling process with rolling temperature ≥1140℃, at least one pass with reduction rate ≥18%, the rough rolling end temperature is controlled at 1130~1180℃ and the reduction rate of this pass is ≥16%; the intermediate billet thickness is ≥ the finished product thickness + 40mm, and the finishing temperature of fine rolling is 780~820℃; after rolling, directly put into water and cool to the target temperature through the MULPIC device at a cooling rate of 3~6℃ / s, and then air-cooled on the cooling bed after hot straightening.

[0021] S5. Post-rolling stack cooling treatment: air-cool the cooling bed to 300-350℃ on the surface, then put it into the insulation pit for stack cooling. The stack cooling time is more than 60 hours. When the surface temperature is less than 90℃, the stack is removed. No heat treatment is required, and fire cutting to size is directly carried out.

[0022] S6. Finished product storage processing.

[0023] As an application of this embodiment: 1. The production method of the small compression ratio high Z-direction performance extra-thick building structure steel plate adopts controlled rolling and controlled cooling (process, which does not require complex quenching / normalizing / tempering heat treatment procedures, and does not require the addition of precious Ni, Mo, Cu and other alloys, which can greatly simplify the production process path, reduce costs and shorten delivery cycles; when the compression ratio is ≤3, the 300mm section continuous casting billet that mainstream steel mills have can replace the large section casting billet / mold casting ingot to roll the maximum thickness of 120mm extra-thick plate, avoiding additional equipment investment, and achieving cost reduction, efficiency improvement, and quality improvement. The adopted differential temperature rolling method can be achieved by using the intermediate water cooling device of the basic equipment of the medium and thick plate production line, and can stably produce extra-thick Q460GJDZ35 steel plates with a maximum thickness of 120mm, and the performance fully meets the requirements of the national standard GBT19879-2023.

[0024] Compared with conventional production methods, the present invention can significantly improve the Z35 qualified rate and ZL average value, the first-time qualified rate of 100-120mm thick Z35 can be stabilized to more than 98%, and the average value can be stabilized to more than 45%; the use of 350mm cross-section continuous casting billets can be expanded, and TMCP rolling can produce 120-140mm thick; the use of 260mm continuous casting billets can be expanded to produce a maximum thickness of 95mm, and the grades cover Q345GJ~Q460GJ, with good scalability.

[0025] The above generally describes the present invention in detail, but it is obvious to a person skilled in the art that some modifications or improvements can be made to the present invention. Therefore, modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A method for producing a very thick building structural steel plate with a small compression ratio and high Z-direction performance, characterized in that: The steps include: S1, molten steel is treated by LF refining and smelting; S2, heating treatment; S3, temperature difference control between slab and intermediate billet; S4, controlled rolling and controlled cooling treatment; S5, cold treatment after rolling; S6. Finished product storage processing.

2. The method for producing a low compression ratio, high Z-direction performance, extra-thick building structural steel plate according to claim 1, characterized in that: The S1 process includes: molten steel is refined by LF, vacuum treated by RH / VD, smelted with strict control of S content, and then cast into 300mm thick continuous casting billets under protection, with 200m of calcium wire fed into each furnace.

3. The method for producing a low compression ratio, high Z-direction performance, extra-thick building structural steel plate according to claim 1, characterized in that: The S2 further includes: the total slab heating time is ≥280min, the soaking temperature is 1170~1260℃, the soaking time is ≥40min, and the core temperature of the cast slab is 1170~1260℃.

4. The method for producing a low compression ratio, high Z-direction performance, extra-thick building structural steel plate according to claim 1, characterized in that: The S3 further includes: using a rough descaling box to extend the water pumping time, descaling the rough rolling mill with descaling water for each pass, and using the header of the intermediate roller of the rough rolling and finishing rolling mills to water-cool the upper and lower surfaces of the slab. After water pumping, the thickness of the sandwich layer on the upper and lower surfaces is greater than 20mm, the temperature difference between the surface and the center of the intermediate slab is greater than 100°C, and the temperature difference between the surface red-return temperature of the intermediate slab at the start of finishing rolling and the center temperature is greater than 50°C, so that greater plastic deformation and stress are introduced into the center of the steel plate during the rolling process.

5. The method for producing a low compression ratio, high Z-direction performance, extra-thick building structural steel plate according to claim 4, characterized in that: The total time of the water pumping time is greater than 15 seconds.

6. The method for producing a low compression ratio, high Z-direction performance, extra-thick building structural steel plate according to claim 1, characterized in that: The S4 includes: adopting two-stage controlled rolling, during the rough rolling process with a rolling temperature ≥1140°C, at least one pass has a reduction rate ≥18%, the rough rolling end temperature is controlled to be 1130~1180°C and the reduction rate of this pass is ≥16%; the intermediate billet thickness is ≥ the finished product thickness + 40mm, and the finishing temperature of the fine rolling is 780~820°C; after rolling, directly entering water to cool to the target temperature through a MULPIC device at a cooling rate of 3~6°C / s, and then being air-cooled on a cooling bed through hot straightening.

7. The method for producing a low compression ratio, high Z-direction performance, extra-thick building structural steel plate according to claim 1, characterized in that: The S5 further comprises: air cooling on the cooling bed until the surface temperature reaches 300-350°C, and then the stacks are put into the heat preservation pit for stack cooling, wherein the stack cooling time is greater than 60 hours, and when the surface temperature is less than 90°C, the stacks are removed without heat treatment and directly subjected to fire cutting to length.