CA3194610A1 - Thin gauge ar450 steel plate and manufacturing method thereof - Google Patents

Thin gauge ar450 steel plate and manufacturing method thereof

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Publication number
CA3194610A1
CA3194610A1 CA3194610A CA3194610A CA3194610A1 CA 3194610 A1 CA3194610 A1 CA 3194610A1 CA 3194610 A CA3194610 A CA 3194610A CA 3194610 A CA3194610 A CA 3194610A CA 3194610 A1 CA3194610 A1 CA 3194610A1
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Prior art keywords
steel plate
slabs
rolling
thickness
compound
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CA3194610A
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French (fr)
Inventor
Jun Huang
Yuandong LUO
Yun Bai
Jingtao Li
Xiaohong Xu
Tao Lin
Jianpeng WU
Chenxiao LI
Meiling HOU
Xianpeng ZI
Peirong ZHOU
Hailong Xu
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Jiangyin Xingcheng Special Steel Works Co Ltd
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Jiangyin Xingcheng Special Steel Works Co Ltd
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Publication of CA3194610A1 publication Critical patent/CA3194610A1/en
Pending legal-status Critical Current

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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18Hardening; Quenching with or without subsequent tempering
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226Hot rolling
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C33/00Making ferrous alloys
    • C22C33/04Making ferrous alloys by melting
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/06Ferrous alloys, e.g. steel alloys containing aluminium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

The invention relates to a thin gauge AR450 steel plate. Chemical compositions of the steel plate include: C: 0.15-0.30, Si: 0.25-0.45, Mn: 0.80-1.20, Cr: 0.20-0.60, Mo: 0.10-0.50 , Ni: 0.10-0.50, Al: 0.02-0.08, B: 0.0010-0.0030, P ? 0.020, S ? 0.010, and balance being Fe and unavoidable impurities. The main path of a process is: steelmaking ? continuous casting ? slab compounding or prefabricated intermediate slab compounding ? rolling ? quenching (determine whether to quench after splitting according to a thickness of the steel plate) ? tempering ? finishing ? inspection ? storage. The thickness of the steel plate prepared by the present invention is 4-8 mm, the maximum width of the steel plate is up to 3200 mm, and the problems that a width of a hot continuous rolled thin plate is small and parts of wide and thick plate enterprises without rolling equipment cannot produce such thin steel plates are effectively solved.

Description

TECHNICAL FIELD
[01] The present invention relates to a thin gauge AR450 steel plate and a manufacturing method thereof. The present invention belongs to the technical field of special steel smelting.
BACKGROUND ART
[02] As a steel material with high abrasion resistance, low-alloy abrasion-resistant steel plates have been widely used in workplaces with harsh environments, such as mines, railways and metallurgy. In addition to abrasion resistance, the low-alloy abrasion-resistant steel plates also have high strength, good toughness, strong weldability and other characteristics. At present, the low-alloy abrasion-resistant steel plates produced in China are mainly concentrated in AR500 and below grades, among which the use of AR450 steel plates occupies a considerable market share.
[03] The main using thickness of the AR450 steel plates is concentrated below 50 mm, especially the thickness of 8-30 mm, with parts of mechanical equipment as thin as 4 mm.
[04] At present, for wide and thick plate enterprises in the domestic and overseas, except for steel enterprises with continuous rolling equipment, the thinnest limit thickness of steel plates produced by steel plate enterprises is generally 6 mm. However, even 6 mm steel plates are only rolled by rolling mills with furnace coiler equipment because coiling furnaces at both ends of the rolling mill can keep the temperature of the steel plates and even heat the steel plates to ensure the rolling temperature, while the thinnest rolling thickness of the rolling mill without such equipment is only about 8 mm. When the thickness is further reduced, slabs cool rapidly, and the rolling torque force is too large, which affects the life of the equipment; and the rolled steel plates have a poor shape, and it is difficult to control the thickness accuracy, especially for the high-strength steel plates.
[05] Chinese Patent Publication No. CN1121444A discloses a new process for multi-stand tandem pack-rolled sheet production, in which multiple single-roll rolling mills are arranged in tandem. After being heated, a thin slab enters the first rolling mill for single-sheet rolling, the second rolling mill performs two-in-one rolling, and the third rolling mill performs four-in-one rolling. The temperature of each stand is controlled during the rolling process, and the temperature of the third stand and the fourth stand is controlled at 400-500 C. This method is to stack semi-finished products together for rolling in the rolling process, which is only suitable for production of materials with a small unit weight.
[06] The patents such as Chinese Patent Publication No. CN101439348A "A
production process for producing extra-thick plates" and CN101590596A "A
method of producing and manufacturing extra-thick slabs by accumulative pack rolling and welding" all mention a plate compounding manner, that is, two or more continuous casting slabs are adopted for joint rolling. However, the production of thick gauge steel plates is all realized by welding two or more original materials together in the rolling process.
SUMMARY OF THE INVENTION
[07] The technical problem to be solved by the present invention is to provide a 4-8 mm thick AR450 wide plate and a manufacturing method of the same with respect to the above prior art. The maximum width is up to 3200 mm. Not only does the product width exceed the conventional width of hot continuous rolled sheets, but also the problem that some of wide and thick plate enterprises without rolling equipment cannot produce such thin steel plates is solved, the product supply specifications are completed, and market competitiveness is improved.
[08] The technical solution adopted by the present invention to solve the above problems is a 4-8 mm thin gauge AR450 steel plate, chemical compositions of the steel plate include, by weight percentage, C: 0.15-0.30, Si: 0.25-0.45, Mn: 0.80-1.20, Cr:
0.20-0.60, Mo:
0.10-0.50, Ni: 0.10-0.50, Al: 0.02-0.08, B: 0.0010-0.0030, P 5 0.020, S 5 0.010, and the balance being Fe and unavoidable impurities. The carbon equivalent of the finished final steel plate is not more than 0.52%.
[09] The present invention also provides a method of making the above thin gauge AR450 steel plate. The main working procedures of the manufacturing method include:
determining a low carbon-equivalent chemical composition for a 4-8 mm steel plate, and obtaining 150-400 mm thick continuous casting slabs through steelmaking, refining and vacuum continuous casting; compound welding the edges of two slabs of the same dimensions or intermediate slabs having a selected thickness obtained by cogging and rolling, wherein a middle portion of the compounded slab is maintained in a non-vacuum condition;
heating and then rolling the compounded slabs to a selected thickness, wherein the middle portion of the rolled compounded slab is not welded due to the non-vacuum condition, and cutting off the welded edges of the rolled compounded slab to obtain two steel plates; and subjecting each one of the steel plates to heat treatment, and straightening each steel plate before quenching if the each steel plate has a relatively low flatness. The final delivery state of the steel plate produced by the manufacturing method is Q + T, the thickness of the finished product is 4-8 mm, and the maximum width of the steel plate is 3200 mm. The product performance and appearance quality of the steel plates meet GB/T 24186-2009 standards.
[010] The manufacturing method specifically includes the following steps:
[011] I. Slab preparation
[012] (1) Steelmaking: precisely controlling alloying elements in steel to ensure that a carbon equivalent deviation between different heats is not more than 0.02%, wherein precise control of compositions helps to stabilize the performance of large batches of steel plates;
performing LF furnace refining to fully deoxidize and desulfurize; keeping the RH limit vacuum time to be longer than 20 min so as to reduce contents of H and N in the steel; and performing calcium treatment operation to promote modification and floating of inclusions;
[013] (2) Continuous casting of slabs: performing continuous casting on 150-400 mm thick slabs by a straight arc continuous casting machine, realizing low superheat and constant casting speed operation by using a tundish induction heating technology, and realizing production of high-quality continuous casting slabs by adopting technologies such as argon protection and dynamic soft reduction, wherein low-power quality of the casting slabs meets: a center segregation is not greater than Level 1.0 of Class C; a center porosity is not greater than Level 1.0; and there are no other defects such as cracks in triangular areas.
[014] (3) Prefabricating of intermediate slabs, wherein thinner prefabricated intermediate slabs need to be used for production of the 4-5 mm thick steel plate through compound rolling.
The prefabricated intermediate slabs are rolled when the 150-400 mm continuous casting slabs are heated to about 1220 C, and a thickness of the prefabricated intermediate slabs is controlled at 60-100 mm. For steel plates with a thickness > 5-8 mm, 150 mm thick slabs can be used for direct compound rolling, without needing compounding after rolling into the prefabricated intermediate slabs. When a width of the finished steel plates exceeds a width of the continuous casting slabs, it is necessary to roll the slabs and widen them to the prefabricated intermediate slabs with a width larger than that of the finished products, and the maximum width of the prefabricated intermediate slabs is not greater than 3400 mm.
[015] II. Slab finishing and compounding
[016] The appearance quality of the continuous casting slabs or the prefabricated intermediate slabs is inspected according to YB/T 2012, and the slabs with qualified appearance quality are cut into sections according to size requirements of a production plan, surfaces of two slabs with the same size are milled and then welded on the periphery, the middles are subjected to non-vacuum treatment, and a welding width from edges of the slabs is controlled at 50-80 mm. On one hand, it is ensured that the peripheries of the slabs cannot be layered when the slabs are rolled, and on the other hand, the yield of the steel plates must be considered.
[017] III. Compound slab heating and rolling
[018] (1) Compound slab heating: in a low-temperature section, the temperature rises to 850 20 C at a rate of 60-100 C/h, and the temperature is kept for 2-3 hours;
in an intermediate-temperature section, the temperature rises to 1000 20 C at a rate of not more than 120 C/h, and the temperature is kept for 2-3 h; and in a high-temperature section, the temperature rises to 1200-1250 C at a rate of not more than 100 C/h, and the temperature is kept for 5-9 hours. Appropriately reducing the heating rate in the high-temperature section and prolonging the holding time after reaching the required temperature are beneficial to bonding of metal in welding areas.
[019] (2) Compound slab rolling: on a wide and thick plate rolling mill, rolling is performed by 10-15 passes until a thickness is twice a target thickness of the finished single steel plate, and a thickness tolerance of the compound steel plates is controlled at 0-0.6 mm.
During the rolling process, there is no widening rolling, but all longitudinal rolling. During rolling in the first 2 passes, a small rolling reduction is used, and in the middle pass, there are 2-3 passes with a rolling reduction of 30-50 mm, so as to realize welding of the welding area. After passing through a hot straightening machine, the steel plates are cooled on a cooling bed.
When cooled to about 300 C, the steel plate can be straightened on a cold straightening machine if there is a warp.
[020] IV. Steel plate heat treatment
[021] (1) Quenching: the 4-5 mm thick compound steel plate is quenched by a quenching machine. After quenching, the four side edges of the compound steel plate are cut off, and the upper and lower plates are split to obtain two steel plates with the same thickness;
due to the limitations to material hardenability of the compound steel plates with a thickness >
5-8 mm, it is necessary to cut off the four side edges of the compound steel plate and split the upper and lower plates before quenching the single steel plate. A quenching process of the steel plate includes: a heating temperature of 900-940 C, a holding time of (20-25) min + 3 min/mm x steel plate thickness (calculating according to a total thickness of the upper and lower plates for the compound steel plate), and water cooling after furnace discharge.
[022] (2) Tempering: low temperature tempering and furnace discharge are performed on the steel plate by using a continuous furnace. The tempering process includes: the heating temperature of 180-220 C, the holding time of 1-2 hours, and air cooling after furnace discharge.
The warped steel plate can be subjected to strong straightening treatment with temperature after furnace discharge, so that the unevenness of the steel plate is not greater than 5 mm/m.
V. Inspection and examination
[023] The finished AR450 steel plate is inspected for appearance quality according to GB/T 24186-2009, sampled for various performance inspections, and judged according to GB/T
24186-2009 standards.
[024] Compared with the prior art, the present invention has the advantages that:
the present invention provides a manufacturing method of a 4-8 mm AR450 wide plate, and the maximum width is up to 3200 mm; not only the product width exceeds the conventional width of hot continuous rolled sheets, but also the problem that parts of wide and thick plate enterprises without rolling equipment cannot produce such thin steel plates is solved; the product supply specifications are completed; and market competitiveness is improved.
DETAILED DESCRIPTION OF EMBODIMENTS
[025] The present invention will be further described in detail below in conjunction with embodiments and comparative examples.
[026] Embodiment 1
[027] A thin gauge AR450 wide plate involved in this embodiment has a thickness of 4 mm and a width of 3200 mm, and chemical compositions of the plate include, by mass percentage: C: 0.20, Si: 0.35, Mn: 1.10, Cr: 0.30, Mo: 0.20, Ni: 0.20, Al:
0.03, B: 0.0020, P:
0.005, 5: 0.002, and the balance being Fe and unavoidable impurities, and the carbon equivalent is 0.50%.
[028] A manufacturing process of the steel plate is as follows:
Steelmaking ¨> continuous casting ¨> prefabrication of intermediate slabs ¨>
compounding ¨>
rolling ¨> quenching ¨> splitting of upper and lower plates ¨> tempering ¨>
finishing ¨>
inspection ¨> storage.
[029] Specific operation of the main working procedures is as follows:
[030] Steelmaking: five harmful elements in steel are strictly controlled during the steelmaking process, wherein N is not more than 25 ppm, 0 is not more than 8 ppm, and H is not more than 1.2 ppm; and calcium treatment is required in the refining and degassing process to control the size and composition of inclusions.
[031] Continuous casting: molten steel is continuously cast into continuous casting slabs with a thickness of 300 mm and a width of 2500 mm by a straight arc continuous casting machine; the low-power quality of the slabs is: a center segregation is Level 1.0 of Class C; a center porosity is Level 0.5; and there are no other defects such as cracks in triangular areas.
[032] Rolling and compounding of prefabricated intermediate slabs: after being heated, the continuous casting slabs are first subject to widening rolling to 3350 mm and then longitudinal rolling to 65 mm, the hot-rolled steel plate enters a hot straightening machine to be straightened and then cooled in a cooling bed to ensure the flatness of the prefabricated intermediate slabs. The hot-rolled steel plate is cut into two prefabricated intermediate slabs of the same size for surface milling, then four sides of the prefabricated intermediate slabs are subject to compound welding, the middles are in a non-vacuum state, the compound welding positions are within 50-80 mm from the edges of the slabs, and the thickness of the slabs after compounding is 124 2 mm.
[033] Compound slab heating and rolling: the compound slabs are heated in stages, in a low-temperature section, the temperature rises to 850 20 C at a rate of 70 C/h, and the temperature is kept for 2 hours; in an intermediate-temperature section, the temperature rises to 1000 20 C at a rate of 100 C/h, and the temperature is kept for 2 h; and in a high-temperature section, the temperature rises to 1220 20 C at a rate of 80 C/h, and the temperature is kept for 5.5 hours. During the compound slab rolling process, there is no widening rolling, but all longitudinal rolling, and a total of 12 rolling passes, of which the rolling reductions in the first two passes are 5 mm and 8 mm, and the rolling reductions in the fifth pass and the sixth pass are respectively 35 mm and 32 mm; and after passing through a hot straightening machine, the rolled steel plate is cooled on a cooling bed, and there is no obvious warp. The thickness of the rolled compound steel plate is 8.2 mm
[034] Heat treatment: the compound steel plate is heated to 920 C in a continuous furnace, is subjected to heat holding for 48 min, and then enters a quenching machine for water cooling; after the steel plate is cooled, four-side welding areas of the steel plate are cut off, and the upper and lower plates are split to obtain quenched steel plates with a width of 3200 mm;
the quenched steel plates are subjected to tempering heat treatment by the continuous furnace in time, the steel plates are heated to 200 C and subject to heat holding for 1 hour, and then discharged from the furnace; and the steel plates are subjected to strong straightening treatment with the temperature, and an AR450 thin plate with the unevenness not greater than mm/m is obtained.
[035] The AR450 steel plate with a thickness of 4 mm and a width of 3200 mm manufactured by the above manufacturing process has a good shape and uniform hardness, and its main properties are shown in Table 1.
[036] Embodiment 2
[037] A thin gauge AR450 wide plate involved in this embodiment has a thickness of 6 mm and a width of 2500 mm, and chemical compositions of the plate include, by mass percentage: C: 0.19, Si: 0.29, Mn: 1.15, Cr: 0.25, Mo: 0.21, Ni: 0.18, Al:
0.03, B: 0.0018, P:
0.006, 5: 0.002, and the balance being Fe and unavoidable impurities, and the carbon equivalent is 0.49%.
[038] A manufacturing process of the steel plate is as follows:
Steelmaking ¨> continuous casting ¨> compounding ¨> rolling ¨> splitting of upper and lower plates ¨> quenching ¨> tempering ¨> finishing ¨> inspection ¨> storage.
[039] Specific operation of the main working procedures is as follows:
[040] Steelmaking: five harmful elements in steel are strictly controlled during the steelmaking process, wherein N is not more than 25 ppm, 0 is not more than 8 ppm, and H is not more than 1.2 ppm; and calcium treatment is required in the refining and degassing process to control the size and composition of inclusions.
[041] Continuous casting: molten steel is continuously cast into the continuous casting slabs with a thickness of 150 mm and a width of 2600 mm by a straight arc continuous casting machine; the low-power quality of the slabs is: a center segregation is Level 0.5 of Class C; a center porosity is Level 0.5; and there are no other defects such as cracks in triangular areas.
[042] Slab compounding: two continuous casting slabs of the same size are subject to surface milling, and then compound welding is carried out on the peripheries, and the middles are in a non-vacuum state. The compound welding positions are within 50-80 mm from edges of the slabs, and a thickness of the slabs after compounding is 294 2 mm.
[043] Compound slab heating and rolling: the compound slabs are heated in stages, in a low-temperature section, the temperature rises to 850 20 C at a rate of 70 C/h, and the temperature is kept for 3 hours; in an intermediate-temperature section, the temperature rises to 1000 20 C at a rate of 100 C/h, and the temperature is kept for 3 h; and in a high-temperature section, the temperature rises to 1220 20 C at a rate of 80 C/h, and the temperature is kept for 9 hours. There is no widening rolling in the compound slab rolling process, but all longitudinal rolling, and a total of 14 rolling passes, of which the rolling reductions in the first two passes are 5 mm and 8 mm, and the rolling reductions in the fifth pass, the sixth pass and the seventh pass are respectively 50 mm, 50 mm and 45 mm, the rolled steel plate is cooled by a cooling bed after passing through a hot straightening machine, and there is no obvious warp. The thickness of the rolled compound steel plate is 12.3 mm
[044] Heat treatment: before the heat treatment of the compound steel plate, the four-side welded areas are cut off, and the upper and lower plates are split to obtain hot-rolled steel plates with a width of 2500 mm. The split steel plates are heated to 920 C in a continuous furnace, subject to heat holding for 40 min, and then enters a quenching machine for water cooling; tempering heat treatment is performed on the quenched steel plates in time by the continuous furnace, the steel plates are heated to 190 C, subject to heat holding for 1.2 hours, and then discharged from the furnace; and the steel plates are subject to strong straightening treatment with the temperature, and an AR450 thin plate with the unevenness not greater than mm/m is obtained.
[045] The AR450 steel plate with a thickness of 6 mm and a width of 2500 mm manufactured by the above manufacturing process has a good shape and uniform hardness, and its main properties are shown in Table 1.
[046] Embodiment 3
[047] A thin gauge AR450 wide plate involved in this embodiment has a thickness of 8 mm and a width of 3000 mm, and chemical compositions of the plate include, by mass percentage: C: 0.21, Si: 0.25, Mn: 1.11, Cr: 0.25, Mo: 0.23, Ni: 0.17, Al:
0.03, B: 0.0016, P:
0.005, 5: 0.003, and the balance being Fe and unavoidable impurities, and the carbon equivalent is 0.50%.
[048] A manufacturing process of the steel plate is as follows:
Steelmaking ¨> continuous casting ¨> prefabrication of intermediate slabs ¨>
compounding ¨>
rolling ¨> splitting of upper and lower plates ¨> quenching ¨> tempering ¨>
finishing ¨>
inspection ¨> storage.
[049] Specific operation of the main working procedures is as follows:
[050] Steelmaking: five harmful elements in steel are strictly controlled during the steelmaking process, wherein N is not more than 25 ppm, 0 is not more than 8 ppm, and H is not more than 1.2 ppm; and calcium treatment is required in the refining and degassing process to control the size and composition of inclusions.
[051] Continuous casting: molten steel is continuously cast into the continuous casting slabs with a thickness of 370 mm and a width of 2200 mm by a straight arc continuous casting machine; the low-power quality of the slabs is: a center segregation is Level 1.0 of Class C; a center porosity is Level 0.5; and there are no other defects such as cracks in triangular areas.
[052] Rolling and compounding of prefabricated intermediate slabs: after being heated, the continuous casting slabs are first subject to widening rolling to 3150 mm and then longitudinal rolling to 80 mm, the hot-rolled steel plate enters a hot straightening machine to be straightened and then cooled in a cooling bed to ensure the flatness of the prefabricated intermediate slabs. The hot-rolled steel plate is cut into two prefabricated intermediate slabs of the same size for surface milling, then four sides of the prefabricated intermediate slabs are subject to compound welding, the middles are in a non-vacuum state, the compound welding positions are within 50-80 mm from the edges of the slabs, and the thickness of the slabs after compounding is 154 2 mm.
[053] Compound slab heating and rolling: the compound slabs are heated in stages, in a low-temperature section, the temperature rises to 850 20 C at a rate of 70 C/h, and the temperature is kept for 2.5 hours; in an intermediate-temperature section, the temperature rises to 1000 20 C at a rate of 100 C/h, and the temperature is kept for 2.5 h;
and in a high-temperature section, the temperature rises to 1220 20 C at a rate of 85 C/h, and the temperature is kept for 6.5 hours. During the compound slab rolling process, there is no widening rolling, but all longitudinal rolling, and a total of 12 rolling passes, of which the rolling reductions in the first two passes are 5 mm and 8 mm, and the rolling reductions in the fifth pass and the sixth pass are 50 mm and 45 mm respectively, after passing through a hot straightening machine, the rolled steel plate is cooled by a cooling bed , and there is no obvious warp. The thickness of the rolled compound steel plate is 16.3 mm.
[054] Heat treatment: before the heat treatment of the compound steel plate, the four-side welded areas are cut off, and the upper and lower plates are split to obtain hot-rolled steel plates with a width of 3000mm. The split steel plates are heated to 910 C in a continuous furnace, subjected to heat holding for 46min, and then enters a quenching machine for water cooling; tempering heat treatment is performed on the quenched steel plates in time by the continuous furnace, the steel plates are heated to 200 C, heat holding is performed for 1.5 hours, and then discharged from the furnace; and the steel plates are subject to strong straightening treatment with the temperature, and an AR450 thin plate with the unevenness not greater than 5 mm/m is obtained.

Table 1 Mechanical properties and unevenness conditions of AR450 steel plates produced in each embodiment Surface Tensile Elongation Brinell Unevenness Embodiment Thickness/mm strength after breaking Hardness mm/m Rrn/M Pa Asornm/%
H BW

2.5 3 8 1465 9.5 448 2.5
[055] In addition to the above embodiments, the present invention also includes other implementations, and all technical solutions formed by equivalent transformation or equivalent replacement shall fall within the protection scope of the claims of the present invention.

Claims (7)

1. A thin gauge AR450 steel plate, characterized in that, the steel plate has a chemical composition comprising, by weight percentage:
C: 0.15-0.30, Si: 0.25-0.45, Mn: 0.80-1.20, Cr: 0.20-0.60, Mo: 0.10-0.50, Ni:
0.10-0.50, Al:
0.02-0.08, B: 0.0010-0.0030, P ~ 0.020, S ~ 0.010, and balance being Fe and unavoidable impurities.
2. The thin gauge AR450 steel plate according to Claim 1, characterized in that, a carbon equivalent of the final finished steel plate is not more than 0.52%.
3. The thin gauge AR450 steel plate according to Claim 1, characterized in that, the final finished steel plate has a thickness of 4-8 mm, a maximum width up to 3200 mm, and an unevenness of not greater than 5 mm/m.
4.A method of making a thin gauge AR450 steel plate of Claim 1, characterized in that, the method includes:
determining a low-carbon-equivalent chemical composition for a 4-8 mm steel plate, and obtaining 150-400 mm thick continuous casting slabs through steelmaking, refining and vacuum continuous casting;
compound welding edges of two slabs having same dimensions or two intermediate slabs having a thickness obtained by cogging and rolling, a middle portion of the compounded slab maintained under a non-vacuum condition;
heating and then rolling the compounded slab to a selected thickness, wherein the middle portion of the rolled compounded slab is not welded due to the non-vacuum condition, and cutting off the welded edges of the rolled compounded slab to obtain two steel plates; and subjecting each one of the steel plates to heat treatment, and straightening each steel plate before quenching if the each steel plate has a relatively low flatness.
5. The method of Claim 4, characterized in that, the method comprises the following steps:
I. Slab preparation (1) Steelmaking, precisely controlling alloying elements in steel to ensure that a carbon equivalent deviation between different heats is not more than 0.02%, performing LF furnace refining to fully deoxidize and desulfurize, and keeping RH limit vacuum time to be longer than 20 min;
(2) Continuous casting of slabs: performing continuous casting on 150-400 mm thick slabs by a straight arc continuous casting machine, and realizing production of high-quality continuous casting slabs by using a tundish induction heating technology and adopting argon protection and dynamic soft reduction technologies, wherein the low-power quality of the casting slabs meets: a center segregation is not greater than Level 1.0 of Class C, and a center porosity is not greater than Level 1.0;
(3) Prefabrication of intermediate slabs: for production of 4-5 mm thick steel plates, performing compound rolling on thinner prefabricated intermediate slabs, rolling 150-400 mm continuous casting slabs heated to about 1220 C to obtain the prefabricated intermediate slabs, and controlling a thickness of the prefabricated intermediate slabs at 60-100 mm; and for steel plates with a thickness > 5-8 mm, performing direct compound rolling on 150 mm thick slabs without needing compounding after rolling into the prefabricated intermediate slabs, and when a width of the finished steel plate exceeds the width of the continuous casting slabs, rolling and widening the slabs to the prefabricated intermediate slabs with the width larger than that of the finished product, wherein a maximum width of the prefabricated intermediate slabs is not greater than 3400 mm;
II. Slab finishing and compounding Inspecting the appearance quality of the continuous casting slabs or the prefabricated intermediate slabs according to YB/T 2012, and cutting the slabs with qualified appearance quality into sections according to size requirements of a production plan, milling surfaces of two slabs with the same dimensions and then welding the edges of the two slabs, wherein the middle portion is subjected to non-vacuum treatment, and a welding width from the edges of the slabs is controlled at 50-80 mm;
III. Compound slab heating and rolling (1) Compound slab heating: increasing a temperature in a low-temperature section 850 20 C at a rate of 60-100 C/h, and holding the temperature for 2-3 hours;
increasing a temperature in an intermediate-temperature section to 1000 20 C at a rate of not more than 120 C/h, and holding the temperature in the intermediate-temperature section for 2-3 h; and increasing a temperature in a high-temperature section to 1200-1250 C at a rate of not more than 100 C/h, and holding the temperature in the high-temperature section for 5-9 hours;
(2) Compound slab rolling: on a wide and thick plate rolling mill, rolling for 10-15 passes until a rolled thickness is twice the selected thickness of the finished single steel plate, wherein a thickness tolerance of the compound steel plate is controlled at 0-0.6 mm; and after passing through a hot straightening machine, cooling the steel plate on a cooling bed to about 300 C;
IV. Steel plate heat treatment (1) Quenching: wherein a quenching process of the steel plate includes: a heating temperature of 900-940 C, a holding time of 20-25 min + 3min/mm x steel plate thickness, calculating according to a total thickness of upper and lower plates, and water cooling after furnace discharge;
(2) Tempering: performing low temperature tempering on the steel plate in a continuous furnace and then discharging the steel plate from the furnace, wherein the tempering process is performed at a heating temperature of 180-220 C, a holding time of 1-2 hours, and with air cooling after furnace discharge;
V. Inspection and examination inspecting the finished AR450 steel plate for appearance quality according to GB/T
24186-2009, and sampling for various performance inspections, according to standards.
6. The method of Claim 4, characterized in that, the rolling of the compound slabs comprises only longitudinal rolling without widening rolling wherein a small rolling reduction is used in the first two rolling passes and a rolling reduction of 30-50 mm is used in 2-3 middle passesõ to achieve welding in welding areas.
7. The method of Claim 4, characterized in that, at a steel plate quenching stage, the 4-5 mm thick compound steel plate is quenched by a quenching machine; after quenching, the four side edges of the compound steel plate are cut off, and the upper and lower plates are split to obtain two steel plates with the same thickness; and the four side edges of the compound steel plate with the thickness > 5-8 mm are cut off, and the single steel plates are quenched after the upper and lower plates are split.
CA3194610A 2021-03-24 2021-11-19 Thin gauge ar450 steel plate and manufacturing method thereof Pending CA3194610A1 (en)

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