Wear-resistant cladding strip having Anti-delayed-cracking characteristics, and production method

Abstract

Disclosed are a wear-resistant cladding strip having anti-delayed-cracking characteristics, and a production method, comprising a steel substrate and a low-alloy steel layer or a copper layer on at least one surface thereof, a transition layer being formed at a contact interface between the steel substrate and the low-alloy steel layer or the copper layer. The produced cladding strip has good interfacial bonding performance, cold-bending workability and surface quality, a yield strength ≥1100 MPa, a tensile strength ≥1250 MPa, and an elongation ≥6%, meets D＝3a / 4a / 6a and 90° bending processing requirements, and is suitable for the production and processing of structural components in the field of construction machinery. Moreover, the present invention achieves the cladding of steel and steel or copper in a conventional steel continuous hot rolling production process, omitting complicated billet assembly and welding procedures in existing cladding production processes, and resulting in higher production efficiency and lower costs.

Description

Abrasion-resistant cladding plate strip with delayed cracking resistance and method of production TECHNICAL FIELD

[0001] The present application belongs to the field of low alloy cladding material manufacturing, and particularly relates to an abrasion-resistant cladding plate strip with delayed cracking resistance and a production method. BACKGROUND

[0002] In the reclamation, channel dredging, and embankment maintenance operations, a large amount of solid particles such as silt and gravel are transported in the form of slurry through the dredging pipeline for a long distance. The pipeline simultaneously bears the electrochemical corrosion of the slurry medium and the abrasion of the solid particles and the interaction of the two. In particular, the abrasion of the inner wall of the pipe body is more serious when the seawater slurry contains weathered rock, coral reefs, and medium-coarse sand. Therefore, the steel for the dredging pipe not only requires abrasion resistance but also corrosion resistance, thereby having good abrasion resistance. In order to reduce the dredging cost, a higher strength abrasion-resistant steel plate is required to make the dredging pipe to improve the service life of the pipeline.

[0003] In the dredging operation, the dredging pipeline as an important component faces the problem of corrosion on the inside and outside of the pipe body during use. The outer wall of the pipe body inevitably bears bumps and scratches from hard objects. When the strength of the pipe body steel plate is low, such as Q235B and 3Q345B, the impact energy can be absorbed by the deformation of the low yield strength of the steel plate itself to ensure the safety of the pipe body. However, for high-strength steel plates, especially ultra-high-strength steel plates with a yield strength exceeding 1000 MPa, it is difficult for the damage stress to exceed the yield strength of the steel plate to cause deformation when such damage occurs, thereby leading to the initiation and propagation of cracks at the damaged location. In a corrosive environment, the initiation and propagation of cracks promote the penetration and diffusion of hydrogen, and electrochemical corrosion also promotes the precipitation and aggregation of hydrogen. Hydrogen atoms penetrate into the steel lattice, increasing the vacancy concentration, and further forming micro-pores of vacancy clusters, which further promote the initiation of micro-cracks, leading to brittle cracking of the steel plate, i.e. delayed cracking. This will significantly affect the normal operation of the dredging operation and shorten the service life of the dredging pipeline, increasing the dredging cost. The higher the strength of the steel plate, the more susceptible it is to hydrogen penetration. Therefore, under the dredging working conditions, even if the surface of the pipe body is not damaged, there is still a problem of delayed cracking caused by hydrogen. High-strength steel plates used for dredging pipelines must consider delayed cracking resistance in terms of performance.

[0004] Chinese patent CN108930001B discloses a high-hardness abrasion-resistant steel plate for slurry dredging and a production method thereof, which discloses an abrasion-resistant steel plate with a hardness of 450 HBW. Although its abrasion-resistant performance can be twice that of ordinary abrasion-resistant steel, the component design does not consider hydrogen penetration and corrosion stress of high-strength steel plates during construction, and there is a problem of delayed cracking.

[0005] With the increasing use requirements, it is difficult for single material to meet the performance requirements in many aspects. The composite plate prepared by selecting multiple metal materials through various processes has the advantages of multiple metals, thereby being able to meet the needs of engineering applications.

[0006] At present, the common composite plate has copper, aluminum or titanium-steel, stainless steel-steel composite materials, and there are many patents for the cladding materials and preparation.

[0007] Chinese patents CN201645923U and CN201721090U disclose a "copper steel copper clad strip" and a "copper-mild steel composite plate", which are a copper steel combined strip and plate respectively. The former does not involve specific methods, and only stipulates that the Cu content in the copper clad strip is 5-20%; the latter is to stack the copper plate and the steel plate after cleaning the surface, and then roll after heating, which is low in efficiency.

[0008] Chinese patent CN113106327B discloses a "high corrosion-resistant strip steel and its manufacturing method", which obtains a stainless steel-steel cladding material by cladding stainless steel on the surface of carbon steel, that is, has the corrosion resistance of stainless steel, while greatly reduces the cost. However, the patent involves complex grouping technology, including surface pickling, polishing treatment, welding, vacuum extraction, etc., and then uses conventional hot continuous rolling process to complete the production of the strip steel, which has a complex preparation process of the composite blank and high production cost.

[0009] From the existing technology, the high-strength steel grade for engineering machinery needs to add more Cr, Ni, Mo, Nb, V and other elements, which is high in cost and difficult to meet the forming performance requirements. The limited few cladding plates and preparation technologies involve materials that are low in strength and not suitable for engineering machinery field, or the cladding process is complex and high in cost. SUMMARY

[0010] The purpose of the present application is to provide a wear-resistant cladding plate strip with anti-delay cracking characteristics and a manufacturing method thereof, which has good interface bonding performance, cold bending processing performance and surface quality, and is suitable for the production and processing of structural parts in the engineering machinery field. Moreover, the present application realizes the cladding of steel or copper with steel in the existing hot continuous rolling production process, omits the complex grouping and welding process in the existing cladding production process, is higher in production efficiency and lower in cost. In addition, the cladding process of the present application is suitable for various types of cladding and steel base plates. According to the selected cladding and steel base plate materials, cladding plate strips meeting different cold bending processing requirements can be obtained.

[0011] To achieve the above purpose, the first aspect of the present application provides an anti-delay cracking wear-resistant cladding plate strip, which comprises a steel base plate and a cladding layer on at least one surface of the steel base plate, and a transition layer formed at the contact interface between the steel base plate and the cladding layer.

[0012] said cladding is a low-alloy steel layer or a copper layer,

[0013] said low-alloy steel comprises, in addition to Fe and inevitable impurities, the following chemical composition in weight percent: C: 0.001-0.04%, Si≤0.1%, Mn: 0.05-0.20%, P≤0.015%, S≤0.006%, Al: 0.01-0.04%, Ti: 0.01-0.04%, N≤0.005%;

[0014] said low-alloy steel has a tensile strength ≤ 350 MPa, preferably 280-350 MPa, a hardness ≤ 120 Hv, preferably 90-120 Hv, and an elongation ≥ 30%.

[0015] Preferably, the low-alloy steel has the following chemical composition in weight percent: C: 0.001-0.04%, Si≤0.1%, Mn: 0.05-0.20%, P≤0.015%, S≤0.006%, Al: 0.01-0.04%, Ti: 0.01-0.04%, N≤0.005%, the balance being Fe and inevitable impurities.

[0016] Preferably, the steel substrate comprises the following chemical composition in weight percent: C: 0.19-0.25%, Si: 0.1-0.3%, Mn: 1.0-1.4%, P≤0.015%, S≤0.006%, Al: 0.01-0.04%, Cr: 0.1-0.3%, Cu: 0.1-0.3%, Ni: 0.1-0.3%, B: 0.001-0.003%, N≤0.005%, Nb: 0.01-0.03%, the balance being Fe and inevitable impurities; the steel substrate has a hardness ≥ 450 HBW; more preferably, the cladded strip has a thickness of 8-20 mm, the low-alloy steel layer or the copper layer has a thickness of 0.8-5.0% of the total thickness of the cladded strip, and / or the cladded strip has a yield strength ≥ 1200 MPa, a tensile strength ≥ 1400 MPa, and an elongation ≥ 12%, meeting the 90° bending requirement of D = 6a.

[0017] Preferably, the cladding layer of the clad plate strip of the present application is a low alloy steel layer, the steel substrate comprises the following chemical components in percentage by weight: C: 0.18-0.24%, Si: 0.1-0.3%, Mn: 0.6-0.9%, P≤0.015%, S≤0.006%, Al: 0.01-0.04%, Cr: 0.1-0.3%, N≤0.005%, Ti: 0.01-0.03%, B: 0.001-0.003%, the balance being Fe and inevitable impurities, the tensile strength of the steel substrate is ≥1300 MPa, the hardness is ≥420 HBW; more preferably, the thickness of the clad plate strip is 1.5-8.0 mm, the thickness of the low alloy steel layer is 1.5-12% of the total thickness of the clad plate strip, and / or the yield strength of the clad plate strip is ≥1100 MPa, the tensile strength is ≥1250 MPa, the elongation is ≥10%, and the 90° bending requirement of D=3a is met.

[0018] Preferably, the cladding layer of the clad plate strip of the present application is a low alloy steel layer, the steel substrate comprises the following chemical components in percentage by weight: C: 0.26-0.31%, Si: 0.1-0.3%, Mn: 0.8-1.2%, P≤0.015%, S≤0.006%, Al: 0.01-0.04%, Cr: 0.1-0.3%, Ni: 0.1-0.3%, N≤0.005%, Ti: 0.01-0.03%, B: 0.001-0.003%, the balance being Fe and inevitable impurities, the tensile strength of the steel substrate is ≥1600 MPa, the hardness is ≥470 HBW; more preferably, the thickness of the clad plate strip is 1.5-8.0 mm, the thickness of the low alloy steel layer is 1.5-14% of the total thickness of the clad plate strip, and / or the yield strength of the clad plate strip is ≥1300 MPa, the tensile strength is ≥1450 MPa, the elongation is ≥6%, and the 90° bending requirement of D=4a is met.

[0019] Preferably, the microstructure of the low alloy steel of the present application is equiaxed ferrite, and the grain size is ≥10 μm, preferably 10-100 μm.

[0020] The steel plate generally improves the strength through solid solution strengthening, precipitation strengthening, dislocation strengthening and grain boundary strengthening. The low alloy steel used as the cladding layer in the present application requires excellent plasticity, i.e. equiaxed ferrite structure is maintained even under quenching cooling conditions, so as to control the tensile strength below 350 MPa. In order to effectively reduce the yield strength and improve the elongation, the addition amount of alloying elements must be reduced as much as possible, and the strengthening factors must be reduced. The reasons for designing the specific chemical components of the low alloy steel cladding layer of the present application are as follows:

[0021] C is a solid solution strengthening element, which can increase the yield strength and decrease the elongation. The content of C should be as low as possible. When the content of C is higher than 0.04%, pearlite structure is easily formed in the steel, and even martensite structure is formed during the cooling process, which is not good for the plasticity and cold bending performance. Therefore, the content of C is controlled to be 0.001-0.04% in the present application.

[0022] Si is a deoxidizing element and a solid solution strengthening element, which can increase the yield strength and decrease the elongation. Therefore, the addition amount of Si should be as low as possible. Therefore, the content of Si is controlled to be ≤0.1% in the present application.

[0023] Mn is a common strengthening element in steel, which can increase the yield strength through solid solution strengthening and decrease the elongation. Therefore, the content of Mn is controlled to be 0.05-0.20% in the present application.

[0024] P can increase the strength of the steel plate, but can make the steel plate brittle and affect the toughness. Therefore, the content of P in the steel should be as low as possible. Therefore, the content of P is controlled to be ≤0.015% in the present application.

[0025] S can increase the yield strength of the steel, but can make the steel plate brittle and decrease the low-temperature toughness of the steel. Therefore, the content of S is controlled to be ≤0.006% in the present application.

[0026] Al is a ferrite-forming element, which is usually added in the steel as a deoxidizing agent during the steelmaking process. A small amount of Al forms fine AlN precipitates during the steelmaking process, which has the effect of refining the austenite grains during the subsequent cooling process, and improves the strength and toughness of the steel. Al is also used as a N fixing agent in the steel. When AlN exists independently as a non-metallic inclusion in the steel, it destroys the continuity of the steel matrix, especially when the content of Al is high, the amount of AIN is large and the AIN is distributed in aggregation, which is more harmful, and at the same time, the oxides with poor plasticity are formed. Therefore, the content of Al is controlled to be 0.01-0.04% in the present application.

[0027] N can significantly increase the strength of the steel through solid solution. N can form precipitates with Al and Ti in the steel, and the fine precipitates have the effect of pinning the grain boundaries to refine the austenite grains. N forms AlN particles with Al in the steel, which has the effect of binding Al and limiting the diffusion of Al in the steel. Higher N easily forms AlN in the steel, which significantly increases the amount of nitrides in the steel. Higher N easily accumulates at the defects of the steel, which deteriorates the low-temperature impact toughness. Therefore, the content of N is controlled to be ≤0.005% in the present application.

[0028] Ti can fix C, N atoms to reduce their resistance to dislocation movement. Ti can form TiN→Ti4C2S2→TiS and TiC in steel in turn, eliminating free C, N atoms in steel, thereby reducing the yield strength. At the same time, the coarsening of TiC, TiN particles makes them lose the grain boundary pinning effect, increases the grain size, reduces the grain boundary strengthening effect, and obtains equiaxed ferrite matrix structure. However, too much Ti will reduce the elongation of the steel plate. Therefore, the Ti content is controlled at 0.01-0.04%.

[0029] The low alloy steel used in the application adopts extremely low C-Si-Mn component design and fixes C, N interstitial atoms by Ti, eliminates the solid solution strengthening effect of C, N atoms, and utilizes the coarse TiN, TiC particles to obtain larger grain size, so that the surface layer of the low strength steel can still obtain equiaxed ferrite matrix structure even in the quenched state, and the hardness value is not more than 120Hv.

[0030] The steel substrate used in the application requires high strength and certain corrosion resistance to meet the requirements of wear resistance and corrosion resistance. The substrate mainly obtains high strength through phase transformation strengthening of C, and further improves the strength and toughness and inhibits corrosion through Cr, Cu, Ni, Nb, B, etc. Therefore, the following three kinds of steel substrate component design (wt%) are preferably used:

[0031] I. C: 0.19-0.25%, Si: 0.1-0.3%, Mn: 1.0-1.4%, P≤0.015%, S≤0.006%, Al: 0.01-0.04%, Cr: 0.1-0.3%, Cu: 0.1-0.3%, Ni: 0.1-0.3%, B: 0.001-0.003%, N≤0.005%, Nb: 0.01-0.03%, the balance being Fe and unavoidable impurities.

[0032] II. C: 0.18-0.24%, Si: 0.1-0.3%, Mn: 0.6-0.9%, P≤0.015%, S≤0.006%, Al: 0.01-0.04%, Cr: 0.1-0.3%, N≤0.005%, Ti: 0.01-0.03%, B: 0.001-0.003%, the balance being Fe and unavoidable impurities

[0033] III. C: 0.26-0.31%, Si: 0.1-0.3%, Mn: 0.8-1.2%, P≤0.015%, S≤0.006%, Al: 0.01-0.04%, Cr: 0.1-0.3%, Ni: 0.1-0.3%, N≤0.005%, Ti: 0.01-0.03%, B: 0.001-0.003%, the balance being Fe and unavoidable impurities

[0034] The design concept of the chemical elements of the steel base plate is as follows:

[0035] C is the most economical strengthening element in the steel, but too high C makes the high-temperature steel billet prone to cracking during the cooling process, which is not conducive to the preservation of the steel billet and increases the production difficulty, therefore, the content of C in the steel base plate of the present application is controlled to be 0.18-0.31%.

[0036] Si is a deoxidizing element and also a solid solution strengthening element, Si replaces Fe atoms in the steel in a substitutional manner, hinders dislocation movement and thus realizes solid solution strengthening. Si can reduce the diffusion coefficient of C in ferrite, increase the activity of carbon, inhibit the formation of carbides, and inhibit the precipitation of coarse carbides at defects to improve toughness, and improve the purity of the steel. At the same time, Si is also a corrosion-resistant element, Si can form complex oxides with other elements such as Ca and Al, SiO2 is an acidic oxide, which can weaken the alkalization caused by Ca, so that the pH value of the corrosion interface is suitable for the formation of a protective rust layer. However, too high Si promotes the graphitization of C, which is not conducive to toughness; at the same time, it is not conducive to the surface quality and welding performance. Moreover, the wear-resistant steel does not want the surface to easily form a rust layer. Therefore, the content of Si in the steel base plate of the present application is controlled to be 0.1-0.3%.

[0037] Mn is a common strengthening element in steel and also a necessary element for deoxidization of steelmaking, which promotes the formation of austenite. Mn improves the yield strength through solid solution strengthening, and reduces the elongation. An appropriate amount of Mn can combine with S in the steel to form MnS, reducing the thermal brittleness of the steel. Too high Mn hinders the recovery of the structure and inhibits the growth of recrystallized grains, reducing the strength of γ texture (ND||<111), which is very unfavorable for the stamping forming of the steel plate. Therefore, the content of Mn in the steel base plate of the present application is controlled to be 0.6-1.4%.

[0038] P is the main corrosion-resistant element in traditional atmospheric corrosion-resistant steel, which promotes the formation of a protective rust layer on the surface and effectively improves the atmospheric corrosion resistance of the steel, but the formation of the rust layer on the surface will accelerate the abrasion loss of the material during the abrasion process, reducing the abrasion resistance. At the same time, the presence of P easily causes segregation, reducing the toughness and plasticity of the steel and making the steel plate brittle, which affects the toughness, so the content of P in the steel should be reduced as much as possible, therefore, the content of P in the steel base plate of the present application is controlled to be ≤0.015%.

[0039] S can improve the yield strength of the steel, but the presence of S will deteriorate the atmospheric corrosion resistance of the steel and make the steel plate brittle, reducing the low-temperature toughness of the steel, therefore, the content of S in the steel base plate of the present application is controlled to be ≤0.006%.

[0040] Al is usually added in steel as a deoxidizer in the steelmaking process. A trace amount of Al is beneficial to refine the grain and improve the strength and toughness of the steel. However, too much Al will increase the brittleness of ferrite in the steel and reduce the toughness of the steel. Therefore, the content of Al in the steel substrate of the present application is controlled to be 0.01-0.04%.

[0041] Cr has a solid solution strengthening effect and is the element with the smallest contribution coefficient to the corrosion resistance index I. Meanwhile, Cr has a significant effect on the potential increase of the matrix. The addition of an appropriate amount of Cr can effectively increase the self-corrosion potential of the steel, inhibit the occurrence of corrosion, thereby effectively reducing the promoting effect of corrosion on material failure during abrasion and improving the abrasion resistance. However, Cr is a valuable alloying element. Therefore, the content of Cr in the steel substrate of the present application is controlled to be 0.1-0.3%.

[0042] Cu has a solid solution and precipitation strengthening effect, and when the content is high, it has a secondary hardening effect at an appropriate temperature, thereby improving the strength. Meanwhile, Cu is one of the elements that improve the corrosion resistance, and the electrochemical potential is higher than that of Fe. Cu is enriched in the inner rust layer of high-strength low-alloy steel, and Cu elements exist in the form of CuO in the inner rust layer, which increases the polarization resistance of the steel and hinders the transmission of corrosive media O2 and water, thereby improving the marine atmospheric corrosion resistance of the steel. In addition, the addition of copper in the steel can inhibit the diffusion of hydrogen, reduce the sensitivity to hydrogen-induced cracking, and has a good Cu2S corrosion product film layer in an environment containing H2S, which protects the matrix and prevents the corrosion of anodic and cathodic reactions in an acidic medium. Too much Cu causes cracks in the billet during heating and hot rolling, which deteriorates the surface properties. Therefore, when Cu is used, the content of Cu in the steel substrate of the present application is controlled to be 0.1-0.3%.

[0043] Nb is a strong nitrogen carbide forming element, which can combine with carbon and nitrogen in the steel to form intermediate phases such as NbC, Nb(CN) and NbN, and the fine carbide particles formed can refine the structure and produce precipitation strengthening effect, thereby significantly improving the strength of the steel plate. However, too much Nb is not conducive to welding. Therefore, when Nb is used, the content of Nb in the steel substrate of the present application is controlled to be 0.01-0.03%.

[0044] Ni exists in the form of solid solution in steel and does not form carbides, and is an austenite forming element. The addition of Ni can lower the austenite transformation temperature and play a role in grain refinement. Ni can improve the low-temperature impact toughness by refining the grain and reducing the stacking fault energy; Ni can inhibit the diffusion interface movement, improve the hardenability and increase the martensite boundary residual austenite film to improve the toughness, which is beneficial to the refinement of the structure after tempering. However, Ni is a valuable element. Therefore, when Ni is used, the content of Ni in the steel substrate of the present application is controlled to be 0.1-0.3%.

[0045] B has good quenching property, thereby improving the hardness of the steel plate, but too high B content is not good for welding, therefore, the B content in the steel plate of the present application is controlled to be 0.001-0.003%.

[0046] Ti is a strong ferrite forming element and carbonitride forming element, and reduces the austenite zone. Ti is easy to form compounds with C, N and the like, and the melting point of the Ti compound is high, which hinders the growth of austenite when heated. Ti reduces the temper brittleness of the steel at 250-400 DEG C, and the combined addition of Ti and B can significantly reduce the temper brittleness. The precipitation strengthening effect of titanium in the proeutectoid ferrite improves the yield strength. When the Ti content is too high, titanium nitride particles are easy to grow and agglomerate at high temperature, which damages the plasticity and toughness of the steel. Therefore, when Ti is used, the Ti content in the steel plate of the present application can be controlled to be 0.01-0.03%.

[0047] The steel plate of the present application adopts a phase transformation strengthening + corrosion control component design, on the one hand, C in the substrate realizes phase transformation strengthening to form a high-hardness martensite structure; at the same time, the addition of corrosion-resistant alloy elements such as Cu, Ni, Cr and Si inhibits the occurrence of corrosion, thereby improving the corrosion resistance of the steel plate.

[0048] The present application realizes high strength while improving the cold working forming performance of the clad plate strip by the component design of the low alloy steel strip and the copper strip, and the cladding of the high-strength steel substrate. Even if the yield strength is greater than or equal to 1100 MPa, it can still meet the requirements of 3a / 4a, even 6a, 90 DEG cold bending.

[0049] The present application increases the high plasticity cladding layer (low alloy steel layer or copper layer) on the surface of the high-strength steel substrate, which can significantly improve the delayed cracking resistance of the clad plate strip. When the dredging pipe is produced by using the clad plate strip, the inner wall is gradually thinned due to the abrasion failure in the service process, and the high plasticity cladding layer on the outer surface of the pipe body provides very good delayed cracking resistance for the pipe body, and the main advantages are as follows:

[0050] ① Avoiding damage of the steel substrate due to collision and scratching in the service process. The abrasion-resistant material dredging pipe has high hardness and high strength, and is easy to initiate cracks or even crack when subjected to scratching or collision in the service and transportation process. The clad plate strip of the present application can ensure the safety of the dredging pipe because the high plasticity cladding layer on the surface can deform to absorb impact energy when subjected to scratching or impact.

[0051] ② Isolation. The existence of the surface cladding layer of the clad plate strip blocks the penetration of external hydrogen to the outer wall of the dredging pipe, and at the same time, it isolates the corrosion medium from directly contacting the steel substrate of the dredging pipe, so that the outer wall of the substrate no longer corrodes, and the generation of hydrogen is also reduced, thereby inhibiting the initiation and propagation of hydrogen-induced cracks.

[0052] ③The initiation and propagation of delayed cracks are delayed. The coating and the steel base plate are metallurgically combined during high-temperature deformation, which increases the energy required for crack initiation and propagation, thereby effectively delaying the initiation and propagation of cracks.

[0053] ④The stress of the dredging pipe body is balanced. The conventional high-strength corrosion-resistant steel has tensile stress on the outer wall and compressive stress on the inner wall during the pipe winding process. Meanwhile, there is also a certain dredging pressure during the dredging process, which also increases the tensile stress on the outer wall of the pipe body. The existence of tensile stress promotes the penetration of hydrogen and the initiation and propagation of cracks. The high-plasticity coating on the surface of the coating steel plate bears part of the tensile stress on the outer wall of the pipe body through metallurgical combination with the steel base plate, balances the stress on the inner and outer walls of the pipe body, and thereby improves the service safety of the dredging pipe.

[0054] In summary, the coating strip effectively improves the corrosion resistance and cold bending forming performance of the coating strip by coating low-alloy steel strips or copper strips on the surface of the steel base plate, is suitable for the manufacture and processing of slurry dredging pipes, and effectively improves the delayed cracking resistance of the corrosion-resistant dredging pipe.

[0055] The second aspect of the present application provides a production method of the above-mentioned delayed cracking-resistant corrosion-resistant coating strip, comprising the following steps:

[0056] 1) smelting and casting to obtain a steel base plate slab;

[0057] 2) heating to heat the slab;

[0058] 3) rough rolling to obtain an intermediate slab, and the cumulative deformation of the rough rolling stage is ≥80%;

[0059] 4) surface treatment

[0060] The surface of the intermediate slab is polished, the surface is treated, the surface of the low-alloy steel strip or the copper strip on the surface of the coating is treated to remove surface stains, and the surface of the low-alloy steel strip or the copper strip on the surface of the coating is treated to remove surface stains;

[0061] 5) finish rolling

[0062] The coating is attached to the intermediate slab, and the coating head is welded to the intermediate slab, and then finish rolling is performed to obtain a coating steel strip;

[0063] 6) cooling and coiling

[0064] 7) heat treatment

[0065] quenching and tempering are performed.

[0066] Preferably, in step 5), the welding method of the low-alloy steel strip and the intermediate slab is laser welding or resistance welding.

[0067] Preferably, in step 7), uncoiling, straightening and cutting are sequentially performed before quenching.

[0068] Preferably, the surface treatment, cladding and welding are all carried out under the protection of a protective atmosphere, which is one or both of N2 and CO2.

[0069] Preferably, in step 2), the heating temperature is 1100-1240℃ and the heating time is ≥2h.

[0070] The heating temperature of the cast slab is 1100-1240℃ and the heating time is ≥2h. If the heating temperature is too high, austenite grains will be coarsened and the surface will be severely oxidized, increasing the loss. If the heating temperature is too low, the rolling load will be increased and the rolling equipment will be damaged. Similarly, if the holding time is too short, the cast slab will not be heated sufficiently, resulting in abnormal structure and temperature in the core and the surface, which will cause the deformation of the surface and the core to be inconsistent during rolling, resulting in poor plate shape. If the holding time is too long, the structure of the cast slab will be coarse and even overburned, resulting in cracking during rolling of the cast slab. Therefore, the heating temperature is selected to be 1100-1240℃ and the heating time is controlled to be ≥2h.

[0071] Preferably, in step 6), the cladded steel strip after finish rolling is water-cooled or air-cooled to 550-750℃ and then coiled.

[0072] Preferably, in step 5), the finish rolling starting temperature is ≥950℃, the finish rolling final rolling temperature is 850-925℃, and the deformation amount during finish rolling is ≥65%, preferably ≥80%.

[0073] Preferably, when the cladding is a copper strip, the temperature of the intermediate slab is additionally controlled to be 980-1080℃ in step 5).

[0074] Preferably, when the cladding is a low-alloy steel, in step 7), the quenching conditions are: quenching temperature ≥(Ac3 of the steel base plate + 5-30℃), quenching holding time ≥2.5×cladding strip thickness (unit: mm), quenching holding time unit: min, after the quenching holding time ends, cooling to room temperature at a speed of ≥50℃ / s, and the tempering conditions are: tempering temperature 180-260℃, tempering holding time 15-60min.

[0075] The present application adopts on-line hot continuous rolling process to realize the production of steel-steel or steel-copper clad plate strip, and utilizes the high-temperature intermediate blank in the hot continuous rolling process to clad with low alloy steel strip or copper strip, thereby saving the complicated assembling process. The key process of the present application is to obtain the clad blank between rough rolling and finish rolling, thereby greatly improving the hardness range of the available steel substrate, and enhancing the wear resistance of the clad plate strip. For example, the steel substrate of the clad plate strip in the prior art can only adopt the steel plate with hardness not higher than 100-130 HBW, while the present application can adopt the steel plate with hardness of at least 420 HBW as the steel substrate of the clad plate strip, and the corresponding tensile strength and yield strength are also significantly higher than those of the steel substrate in the prior art.

[0076] To ensure the recrystallization grain refinement effect to improve the strength and toughness, the cumulative deformation in the rough rolling stage is required to be ≥80%.

[0077] The purpose of the intermediate blank surface polishing is to remove the surface oxide layer, and to improve the roughness, which is beneficial to improve the bonding strength in the cladding rolling process.

[0078] The surface of the low alloy steel strip or copper strip also needs to be pre-treated (such as pickling or degreasing cleaning), and the main purpose is to remove the oxide scale and various surface stains, especially no oil stains. If the surface of the low alloy steel or copper strip is polished in advance, the bonding strength can be further improved.

[0079] The surface treatment, cladding and welding are all carried out under the protection of protective atmosphere, thereby reducing the oxidation of the intermediate blank at high temperature, and improving the bonding strength, and the protective atmosphere is one or both of N2 and CO2.

[0080] The cladding (such as low alloy steel strip or copper strip) is attached to the intermediate blank, and the low alloy steel strip or copper strip is welded with the head of the intermediate blank, and then finish rolling is carried out to obtain the clad strip, and the finish rolling starting temperature is ≥950℃. The high finish rolling temperature can effectively reduce the rolling load, reduce the energy consumption and reduce the cost; but the too high finish rolling temperature requires higher casting blank heating temperature, which increases the heating cost. The finish rolling starting temperature is limited to above 950℃ by comprehensive consideration. The finish rolling final rolling temperature of the steel in the present application is set according to the A c3 temperature of the steel. For example, the A c3When the temperature is 840-860 DEG C, the finish rolling final rolling temperature can be set to be greater than or equal to 880 DEG C. In this way, full austenite zone rolling can be realized, the appearance of mixed crystal in the matrix structure is avoided, and the rolling mill load is stable during rolling. However, if the final rolling temperature is too high, a higher finish rolling starting temperature is required, which increases energy consumption and cost. Moreover, when the copper cladding layer is used, the temperature can even exceed the melting point of the copper cladding layer, which deteriorates the copper-steel bonding performance. In order to ensure the bonding strength of the interface between the cladding layer and the substrate, it is required to control the deformation amount in the finish rolling stage to be greater than or equal to 65%, and preferably greater than or equal to 80%. In addition, when the copper strip is used as the cladding layer and is attached to the intermediate blank, the temperature of the intermediate blank is controlled to be 980-1080 DEG C. If the temperature of the intermediate blank is too high, the surface copper layer is easily melted, which affects the interface bonding strength.

[0081] Then quenching treatment and tempering treatment are carried out, the quenching treatment temperature is 840-860 DEG C, the substrate A is quenched at the quenching treatment temperature for 5-30 minutes, and then is cooled to room temperature. c3 The temperature is greater than or equal to 840 DEG C, the quenching heat treatment holding time is determined according to the thickness of the cladding strip, the quenching heat treatment holding time is greater than or equal to 2.5 times the thickness of the cladding strip, the thickness of the cladding strip is in millimeter, and the quenching holding time is in minute; after the quenching holding is finished, the cladding strip is directly water quenched to room temperature, and the cooling speed is greater than or equal to 50 DEG C / s.

[0082] Then tempering treatment is carried out at a temperature in the range of 180-260 DEG C, the tempering holding time is 15-60 minutes, so as to slow down and eliminate quenching stress and improve toughness.

[0083] The quenched and tempered cladding strip is subjected to finishing treatment (straightening and edge cutting), and is delivered after performance qualification.

[0084] Compared with the prior art, the application also has the beneficial effects as follows:

[0085] In the application, a low alloy steel layer or a copper layer is clad on the surface of a high-strength steel substrate, the produced cladding strip has good anti-delay cracking performance and corrosion resistance, and has good interface bonding performance, cold bending processing performance and surface quality, and has high strength and excellent forming performance, the yield strength is greater than or equal to 1100 MPa, the tensile strength is greater than or equal to 1250 MPa, and the elongation is greater than or equal to 6%, which meets the requirements of D=3a / 4a or 6a, 90 DEG bending. However, the forming performance of the existing high-strength steel with a strength greater than 960 MPa can only meet the requirements of D=7a-8a, 90 DEG cold bending.

[0086] The clad steel plate is metallurgically combined in hot-rolled state, a transition layer is formed between the clad layer and the whole surface of the steel base plate, and the bonding force is stronger. When the steel base plate and the low-alloy steel clad layer are clad by the method of the present application, since the steel base plate and the low-alloy steel clad layer used are both steel, there is no problem of diffusion resistance between dissimilar metals at the interface, so the interlayer bonding is good, and no obvious delamination can be seen on the macroscopic cross section. Similarly, when the steel base plate and copper are clad by the method of the present application, the obtained copper-clad plate strip has excellent corrosion resistance of copper and longer service life, and at the same time, copper and steel fully diffuse with each other at the interface at high temperature, realizing sufficient metallurgical combination, so no obvious delamination can be seen on the cross section, and the copper-clad plate strip has good appearance quality and can be used without coating, reducing the coating cost and the comprehensive cost. Moreover, the prepared copper-clad plate strip has a width consistent with conventional hot-rolled steel, and the width can be controlled in a range of 700-1600 mm, which is much higher than that of the copper-clad plate strip prepared by the existing process, and the width range can be further expanded according to the characteristics of the equipment. The copper-clad plate strip has excellent copper-steel bonding performance, stamping and drawing processing performance, high strength, high surface quality, conductivity, heat dissipation, corrosion resistance and aesthetic properties, and can be applied to fields with higher requirements for width, such as heat dissipation, corrosion resistance, decoration or manufacturing of high-strength structural parts, while the width of the copper-clad plate strip that can be produced by the existing technology is not more than 200 mm, and is mainly used in the production of shells and warheads in the military field.

[0087] On the contrary, in the clad layer material obtained by cladding the steel base plate with low-alloy steel or the steel base plate with dissimilar metals (such as steel-aluminum, copper-aluminum or copper-steel, etc.) at room temperature by the existing technology, due to the differences in process and material, the bonding between the clad layer and the base plate is mainly physical bonding (mechanical bite) + local metallurgical bonding, and the bonding strength is limited; at the same time, the width is limited, which limits its industrial application. Moreover, the plasticity of the clad layer plate strip after cold rolling and cladding is low, and further annealing treatment is needed to improve the plasticity, increasing the production cost and the production efficiency. Moreover, the annealing temperature is usually not high, and cannot form complete metallurgical combination between the steel base plate and the clad layer.

[0088] The present application realizes the cladding of the steel base plate and the low alloy steel strip in the finishing rolling stage in the hot continuous rolling production process of the steel plate, realizes the on-line rolling of the steel base plate and the low alloy steel strip, the interlayer metal realizes metallurgical bonding under high temperature rolling, the bonding strength is high, and the layering is not easy; and the complex grouping, welding process in the existing cladding production process is omitted, which is not only high in efficiency, but also low in cost. Similarly, the cladding of the copper strip is introduced in the finishing rolling stage, the on-line rolling of the steel base plate and the copper strip is realized, the reheating and subsequent annealing process in the conventional copper cladding rolling is omitted, which is not only high in efficiency, but also low in cost. In addition, since the cladding plate strip is prepared in the hot continuous rolling process, it has good plasticity and cold forming performance, and the reannealing process after the conventional cold rolling cladding is omitted, which is lower in cost. In the process of preparing the cladding plate strip related by the prior art, the grouping and vacuum welding process are complex, high in cost, and low in production efficiency; and the grouping process has high requirements for the size precision of the bonding surface, and is more difficult to process. BRIEF DESCRIPTION OF DRAWINGS

[0089] Fig. 1 is a schematic view of the cladding plate strip structure according to an embodiment of the present application.

[0090] Fig. 2 is a microstructure photograph of the steel base plate of the cladding plate strip according to embodiment A-1 of the present application.

[0091] Fig. 3 is a microstructure photograph of the low alloy steel layer on the surface of the cladding plate strip according to embodiment A-1 of the present application.

[0092] Fig. 4 is a microstructure photograph of the steel base plate of the cladding plate strip according to embodiment B-1 of the present application.

[0093] Fig. 5 is a microstructure photograph of the low alloy steel layer on the surface of the cladding plate strip according to embodiment B-1 of the present application.

[0094] Fig. 6 is a microstructure photograph of the steel base plate of the cladding plate strip according to embodiment C-1 of the present application.

[0095] Fig. 7 is a microstructure photograph of the low alloy steel layer on the surface of the cladding plate strip according to embodiment C-1 of the present application. DETAILED DESCRIPTION

[0096] The present application will be further described below in conjunction with the embodiments and the drawings.

[0097] The process flow for preparing the cladding plate strip according to the present application is as follows:

[0098] 1) smelting and casting to obtain a steel base plate blank;

[0099] 2) heating to heat the blank;

[0100] 3) rough rolling to obtain an intermediate blank, the cumulative deformation in the rough rolling stage is ≥80%;

[0101] 4) surface treatment

[0102] The intermediate blank is subjected to surface treatment, the surface of the intermediate blank is polished, and the stains on the surface of the cladding are removed;

[0103] 5) finish rolling

[0104] The cladding is attached to the intermediate blank, and the cladding head is welded to the intermediate blank, and then finish rolling is performed to obtain a cladded steel strip;

[0105] 6) cooling and coiling;

[0106] 7) heat treatment, quenching and tempering.

[0107] The structure of the obtained cladded strip is shown in FIG. 1.

[0108] Then, the performances of the cladded strip are tested by the following methods.

[0109] The anti-delay cracking performance: the anti-delay cracking performance of the cladded strip obtained by the present application is evaluated by a U-bending immersion test, and is compared with that of a conventional 450HBW hardness grade wear-resistant steel (comparative example). The specific operation steps are as follows: the sample is bent into a U shape, the sample is loaded to the two sides of the sample in parallel using a clamp, and then is immersed in a 0.1 mol / L hydrochloric acid solution, and the solution is replaced every 24 h. The side edges of the sample of the cladded strip are sealed with insulating resin, and the sample is observed twice a day during the test, and the specific cracking time of the sample is confirmed according to the video playback, and the cracking time of the sample is recorded. The shorter the cracking time of the sample, the greater the hydrogen-induced cracking sensitivity. The immersion test is performed for a total of 1344 h (8 weeks). From the results, the sample of the cladded strip of the present application remains intact until the end of the test, while the 450HBW hardness grade wear-resistant steel of the comparative example is broken at 163 h. It shows that the anti-delay cracking performance of the cladded strip obtained by the present application is obviously improved.

[0110] Metal interface bonding strength:

[0111] According to the standard YS-T 1045-2015, the cladded strip is repeatedly bent to cracking at D = 3a, 4a and 6a, 90°, and whether the bonding is good is confirmed according to whether there is delamination at the cracking. The good bonding is evaluated as "qualified".

[0112] Mechanical performance test method: the yield strength, tensile strength and elongation are tested according to the standard GB / T 228.1, and the cold bending performance is tested according to the standard GB / T 232.

[0113] Hardness test method: the hardness test is performed according to GB / T 231.1.

[0114] A. Manufacturing of anti-delay cracking and erosion-resistant cladded strip

[0115] The chemical composition of the steel substrate used in the clad strip of the present embodiment is shown in Table 1, and the rest includes Fe and inevitable impurity elements.

[0116] The chemical composition of the surface low-alloy steel layer of the clad strip of the present embodiment A-1 to A-4 is shown in Table 2, and the balance is Fe and inevitable impurities; the surface cladding of the present embodiment A-5 to A-8 is copper layer. Among them, the embodiments A-2 and A-8 are double-sided cladding, and the embodiment A-4 is one side copper cladding and one side low-alloy steel cladding.

[0117] Comparative Example 1 is a wear-resistant steel plate BW450 with a hardness level of 450HBW, without cladding.

[0118] Comparative Example 2 is a copper-clad material produced by a room temperature cold rolling process as a prior art, the substrate is F11 steel, and the cladding is H90 brass. In order to meet the production of cold-rolled copper-clad strip, the substrate is low-carbon C-Mn steel, and the strength grade is 350MPa. Too high strength will increase the deformation resistance, even beyond the equipment capacity, resulting in failure to clad. Its production process is: pickling - slitting - surface grinding - room temperature cladding rolling - annealing - flattening. The width of the copper-clad strip of Comparative Example 2 is below 200mm, which is relatively narrow compared with the width of 700-1600mm of the present application, limiting its application. At the same time, the copper-steel interface bonding is mainly realized by physical bonding during cold rolling, and the bonding strength is limited; and the cladding material after cold rolling has almost no plasticity, and must be annealed to restore plasticity, so as to meet the subsequent forming processing requirements. Since the main purpose of annealing is to restore plasticity, the annealing temperature is generally below 700℃, and the copper-steel interface is not sufficient to achieve complete metallurgical bonding, so the interface bonding performance is lower than that of the hot rolling cladding of the present application. The copper-clad material of Comparative Example 2 is 6.8mm substrate + 0.2mm H90 brass, which is cold-rolled to 1.03mm by 3 passes, and needs to be annealed once after each cladding rolling to restore plasticity. Such a large number of annealing also increases the production cost and reduces the production efficiency.

[0119] The production process parameters of the clad strip of the present embodiment are shown in Tables 3 and 4.

[0120] The performance test results of the clad strip of the present embodiment are shown in Table 5.

[0121] Figure 2 is a microstructure photograph of the steel substrate of the clad strip of the present embodiment A-1, from which it can be seen that the steel substrate forms high-strength martensite structure after heat treatment, and the hardness is ≥450HBW.

[0122] Figure 3 is a microstructure photograph of the surface low-alloy steel layer of the clad strip of the present embodiment A-1. As shown in Figure 3, the microstructure of the low-alloy steel layer after heat treatment is still equiaxed ferrite, maintaining low strength and high plasticity.

[0123] Thus, the yield strength ≥ 1200 MPa, the tensile strength ≥ 1400 MPa, the elongation ≥ 6%, the D = 6a, 90° bending requirement is met, and the plasticity is far superior to the existing clad steel strip. The clad and steel substrate interface bonding performance is excellent, and after repeated bending until fracture, there is no delamination at the fracture, and the cold bending processing performance, corrosion resistance, and appearance quality are good, and the coating-free use can be realized.

[0124] B. Manufacturing of easy-to-form clad strip

[0125] The chemical composition of the steel substrate used in the clad strip of the present embodiment is shown in Table 6, and the balance is Fe and inevitable impurities.

[0126] The chemical composition of the surface low-alloy steel layer of the clad strip of the present embodiment is shown in Table 7, and the balance is Fe and inevitable impurities.

[0127] The production process parameters of the clad strip of the present embodiment are shown in Tables 8 and 9.

[0128] The performance of the clad strip of the present embodiment is shown in Table 10.

[0129] Figure 4 is a microstructure photograph of the steel substrate of the clad strip of the present embodiment B-1. As can be seen from the picture, the steel substrate forms high-strength martensite structure after heat treatment, and the tensile strength ≥ 1300 MPa, and the hardness ≥ 420 HBW.

[0130] Figure 5 is a microstructure photograph of the surface low-alloy steel layer of the clad strip of the present embodiment B-1. As can be seen from Figure 5, the microstructure of the low-alloy steel layer after heat treatment is still equiaxed ferrite, maintaining low strength and high plasticity.

[0131] Thus, the yield strength ≥ 1100 MPa, the tensile strength ≥ 1250 MPa, the elongation ≥ 10%, the cold bending performance is excellent, and can meet the 3a, 90° cold bending requirement, and the plasticity is far superior to the existing 1100 MPa strength level clad strip. The clad and steel substrate interface bonding performance is excellent, and after repeated bending until fracture, there is no delamination at the fracture, and the complex processing requirements of high-strength structural parts in the mechanical engineering industry are met.

[0132] C. Manufacturing of easy-to-form high-strength clad strip

[0133] The chemical composition of the steel substrate used in the clad strip of the present embodiment is shown in Table 11, with the balance being Fe and unavoidable impurities.

[0134] The chemical composition of the surface low-alloy steel layer of the clad strip of the present embodiment is shown in Table 12, with the balance being Fe and unavoidable impurities.

[0135] The production process parameters of the clad strip of the present embodiment are shown in Tables 13 and 14.

[0136] The performance of the clad strip of the present embodiment is shown in Table 15.

[0137] Figure 6 is a microstructure photograph of the steel substrate of the clad strip of the present embodiment C-1. As can be seen from the picture, the steel substrate forms a high-strength martensite structure after heat treatment, with a tensile strength ≥ 1600 MPa and a hardness ≥ 470 HBW.

[0138] Figure 7 is a microstructure photograph of the surface low-alloy steel layer of the clad strip of the present embodiment C-1. As can be seen from Figure 7, the microstructure of the low-alloy steel layer after heat treatment is still equiaxed ferrite, maintaining low strength and high plasticity.

[0139] Thus, a clad strip with a yield strength ≥ 1300 MPa, a tensile strength ≥ 1450 MPa, an elongation ≥ 6%, excellent cold bending performance, and meeting the 90° bending requirement of D = 4a, and plasticity far superior to existing 1300 MPa strength level clad strips is obtained. The interface bonding performance between the clad layer and the steel substrate is excellent, and after repeated bending until fracture, there is no delamination at the fracture, meeting the complex processing requirements of high-strength structural parts in the mechanical engineering industry.

[0140] The combination of the various technical features in the present application is not limited to the combination described in the claims or the combination described in the specific embodiments, and all the technical features described in the present application can be freely combined or combined in any manner, unless contradictory.

[0141] It should also be noted that the above enumeration is only a specific embodiment of the present application, and obviously the present application is not limited to the above embodiments, and there are many similar changes. All variations directly derived or thought of by those skilled in the art from the disclosure of the present application shall fall within the scope of protection of the present application.

[0142] The priority of the present application CN202411029444.8, CN202411029447.1 and CN202411029446.1 are hereby incorporated by reference in their entirety.

Claims

1. A coated sheet band, characterized by, The clad strip comprises a steel substrate and a clad layer on at least one face of the steel substrate, the interface between the steel substrate and the clad layer forming a transition layer; The clad layer is a low-alloy steel layer or a copper layer, The low-alloy steel comprises, in addition to Fe and unavoidable impurities, the following chemical composition in weight percent: C: 0.001-0.04%, Si ≤ 0.1%, Mn: 0.05-0.20%, P ≤ 0.015%, S ≤ 0.006%, Al: 0.01-0.04%, Ti: 0.01-0.04%, N ≤ 0.005%. The low-alloy steel has a tensile strength ≤ 350 MPa, preferably 280-350 MPa, a hardness ≤ 120 Hv, preferably 90-120 Hv, and an elongation ≥ 30%.

2. The coated sheet strip of claim 1 wherein, The low-alloy steel comprises, in addition to Fe and unavoidable impurities, the following chemical composition in weight percent: C: 0.001-0.04%, Si ≤ 0.1%, Mn: 0.05-0.20%, P ≤ 0.015%, S ≤ 0.006%, Al: 0.01-0.04%, Ti: 0.01-0.04%, N ≤ 0.005%, the balance being Fe.

3. The coated sheet strip defined in claim 1 or 2, characterized in that The steel substrate comprises the following chemical composition in weight percent: C: 0.19-0.25%, Si: 0.1-0.3%, Mn: 1.0-1.4%, P ≤ 0.015%, S ≤ 0.006%, Al: 0.01-0.04%, Cr: 0.1-0.3%, Cu: 0.1-0.3%, Ni: 0.1-0.3%, B: 0.001-0.003%, N ≤ 0.005%, Nb: 0.01-0.03%, the balance being Fe and unavoidable impurities; the steel substrate having a hardness ≥ 450 HBW.

4. The coated sheet strip defined in claim 1 or 2, characterized in that The clad layer is a low-alloy steel layer, the steel substrate comprising the following chemical composition in weight percent: C: 0.18-0.24%, Si: 0.1-0.3%, Mn: 0.6-0.9%, P ≤ 0.015%, S ≤ 0.006%, Al: 0.01-0.04%, Cr: 0.1-0.3%, N ≤ 0.005%, Ti: 0.01-0.03%, B: 0.001-0.003%, the balance being Fe and unavoidable impurities, the steel substrate having a tensile strength ≥ 1300 MPa and a hardness ≥ 420 HBW.

5. The coated sheet strip defined in claim 1 or 2 wherein, The clad layer is a low-alloy steel layer, the steel substrate comprising the following chemical composition in weight percent: C: 0.26-0.31%, Si: 0.1-0.3%, Mn: 0.8-1.2%, P ≤ 0.015%, S ≤ 0.006%, Al: 0.01-0.04%, Cr: 0.1-0.3%, Ni: 0.1-0.3%, N ≤ 0.005%, Ti: 0.01-0.03%, B: 0.001-0.003%, the balance being Fe and unavoidable impurities, the steel substrate having a tensile strength ≥ 1600 MPa and a hardness ≥ 470 HBW.

6. The coated sheet strip defined in any one of claims 1 to 5, characterized in that, The microstructure of the low-alloy steel is equiaxed ferrite, and the grain size is ≥10 μm, preferably 10-100 μm.

7. The coated sheet strip of any one of claims 1 to 3, wherein, The thickness of the clad strip is 8.0-20 mm, and the thickness of the low-alloy steel layer or the copper layer is 0.8-5.0% of the total thickness of the clad strip.

8. The coated sheet of claim 4 wherein, The thickness of the clad strip is 1.5-8.0 mm, and the thickness of the low-alloy steel layer is 1.5-12% of the total thickness of the clad strip.

9. The coated sheet strip of claim 5 wherein, The thickness of the clad strip is 1.5-8.0 mm, and the thickness of the low-alloy steel layer is 1.5-14% of the total thickness of the clad strip.

10. The coated sheet of claim 3 wherein, The clad strip has a yield strength of ≥1200 MPa, a tensile strength of ≥1400 MPa, and an elongation of ≥12%, and meets the requirement of D=6a and 90° bending.

11. The coated sheet strip of claim 4 wherein, The clad strip has a yield strength of ≥1100 MPa, a tensile strength of ≥1250 MPa, and an elongation of ≥10%, and meets the requirement of D=3a and 90° bending.

12. The coated sheet strip of claim 5 wherein, The clad strip has a yield strength of ≥1300 MPa, a tensile strength of ≥1450 MPa, and an elongation of ≥6%, and meets the requirement of D=4a and 90° bending.

13. A method of manufacturing a coated sheet strip as claimed in any one of claims 1 to 12, characterized in that, The method comprises the following steps performed in sequence: 1) smelting and casting to obtain a slab of steel base plate; 2) heating the slab; 3) rough rolling to obtain an intermediate slab, and the cumulative deformation in the rough rolling stage is ≥80%; 4) surface treatment The surface of the intermediate slab is polished and stains on the surface of the cladding are removed; 5) finish rolling The cladding is attached to the intermediate slab, and the head of the cladding is welded to the intermediate slab, and then finish rolling is performed to obtain a clad steel strip; 6) cooling and coiling; 7) heat treatment Quenching and tempering are performed.

14. The method of claim 13, wherein, In step 5), the welding method for welding the low-alloy steel strip to the intermediate slab is laser welding or resistance welding.

15. The method of claim 13 wherein, In step 7), uncoiling, straightening and cutting are performed in sequence before quenching.

16. The method of claim 13, wherein, The surface treatment, cladding attachment and welding are all performed under the protection of a protective atmosphere, which is one or both of N2 and CO2.

17. The method of claim 13, wherein, In step 2), the heating temperature is 1100-1240℃, and the heating time is ≥2 h.

18. The method of claim 13, wherein, In step 6), the finish-rolled clad steel strip is water-cooled or air-cooled to 550-750℃ before coiling.

19. The method of claim 13, wherein, In step 5), the start temperature of finish rolling is ≥950℃, the finish rolling temperature is 850-925℃, and the deformation in the finish rolling stage is ≥65%, preferably ≥80%.

20. The method of claim 13, wherein, When the cladding is a copper strip, the temperature of the intermediate slab is additionally controlled to be 980-1080℃ in step 5).

21. The method of claim 13, wherein, When the coating is a low alloy steel, in step 7), the quenching conditions are: quenching temperature ≥ (steel base plate A c3 +5~30 ℃), quenching holding time ≥ 2.5 x coating plate strip thickness, the unit of coating plate strip thickness is mm, the unit of quenching holding time is min, after the end of quenching holding, cooling to room temperature at a speed of ≥ 50 ℃ / s, the tempering conditions are: tempering temperature is 180~260 ℃, tempering holding time is 15~60 min.

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