High-toughness hot-rolled pickled steel plate for saw back of double-metal band saw and manufacturing method of high-toughness hot-rolled pickled steel plate

Abstract

The invention discloses a high-toughness hot-rolled pickled steel plate for a bimetal band saw back and a manufacturing method of the high-toughness hot-rolled pickled steel plate. The technical problems that an existing steel plate for the bimetal band saw back is low in toughness and high in manufacturing cost are mainly solved. According to the technical scheme, the high-toughness hot-rolled pickled steel plate for the saw back of the double-metal band saw comprises the following chemical components in percentage by weight: 0.28%-0.33% of C, 0.20%-0.40% of Si, 0.90%-1.10% of Mn, less than or equal to 0.015% of P, less than or equal to 0.003% of S, 3.8%-4.0% of Cr, 1.2%-1.4% of Mo, 0.6%-0.8% of Ni, 0.3%-0.4% of V, 0.05%-0.08% of Al, 0.01%-0.03% of Nb, less than or equal to 0.0060% of N, less than or equal to 0.0002% of H, less than or equal to 0.0012% of O and the balance of Fe and inevitable impurities.

Description

Technical Field

[0001] The invention relates to a back material for making a metal cutting band saw, in particular to a high-strength and tough hot-rolled pickled steel plate for a bimetallic band saw back and a manufacturing method thereof, belonging to the technical field of iron-based alloys. Background Art

[0002] Bimetallic band saws are mainly used to cut various metal substrates, such as copper, aluminum, steel billets, etc. The band saw itself consists of two composite materials, the saw back and the saw teeth, which is an advanced cutting material with the characteristics of high efficiency and low consumption. The saw teeth are usually made of high-speed steel, such as M42, which has high hardness, high wear resistance, and high red hardness. The saw back, as the carrier of the saw teeth, needs to withstand a certain amount of tension and fatigue deformation in different directions, and needs to have the characteristics of high strength, high toughness, and high fatigue resistance.

[0003] Bimetal band saws are heat treated together with the back material and tooth material after composite welding. Therefore, the development and research of saw back materials has always been the focus of industry development.

[0004] Due to the high alloy content of the saw back material, the early production mainly adopted the "electric furnace + square billet + narrow strip" method, which had low material utilization and high cost; the toughness was low: the hot coil needed to be annealed before it could be uncoiled and pickled, otherwise it would easily break.

[0005] The patent application with application publication number CN104451421A discloses a bimetallic band saw steel and its preparation method, the weight percentage of the main chemical composition of which is: C: 0.34-0.45%, Si: 0.2-0.4%, Mn: 0.7-0.9%, Cr: 3.3-3.6%, Ni: 0.5-0.7%, Mo: 0.9-1.2%, V: 0.3-0.4%, Nb: 0.08-0.20%, Al: 0.015-0.05%, and the rest is Fe and inevitable impurities. First of all, the two are completely different in composition, the carbon and alloy element composition of the material is different, and the harmful elements P, S, H, O, etc. are not required; secondly, the tensile strength of the material is only 1700MPa, the elongation is only about 9%, and the toughness is low; the invention adopts the EAF electric furnace + narrow belt method for production, and the production cost is high.

[0006] The patent with publication number CN102337474A discloses a saw blade backing steel and its application in bimetallic band saw blades. In the patent, the C component exceeds 0.5%, the content of Cr and Mo alloy elements is very low, the toughness is low, and the welding performance is poor. In addition, it is also produced by the conventional EAF electric furnace + narrow belt method, which has high production costs.

[0007] The existing hot-rolled pickled steel plate used for the saw back of the bimetallic band saw has low toughness, the steel plate needs to be annealed before pickling, and the manufacturing cost is high. Summary of the invention

[0008] The purpose of the present invention is to provide a high-strength and toughness hot-rolled pickled steel plate for bimetallic band saw back and a manufacturing method thereof, mainly to solve the technical problems of low strength and toughness of the existing hot-rolled pickled steel plate for bimetallic band saw back, the need for annealing before pickling, and high manufacturing cost.

[0009] The technical idea of ​​the present invention is to control the C element matrix content in the steel, add a certain amount of alloy elements such as Cr, Mo, V, Nb, etc., adopt LF furnace + RH furnace double refining, strictly control the composition of harmful elements P, S, N, H, O in the steel, improve the strength, toughness and fatigue performance of the material, and coordinate the hot rolling process to regulate the microstructure of the material, so as to obtain a bimetallic band saw back material steel with good toughness and uniform structure that can be used for direct uncoiling and pickling without annealing first.

[0010] The technical solution of the present invention is a high-strength and tough hot-rolled pickled steel plate for a bimetallic band saw back, wherein the chemical composition by weight is as follows: C: 0.28% to 0.33%, Si: 0.20% to 0.40%, Mn: 0.90% to 1.10%, P≤0.015%, S≤0.003%, Cr: 3.8% to 4.0%, Mo: 1.2%-1.4%, Ni: 0.6%-0.8%, V: 0.3%-0.4%, Al: 0.05% to 0.08%, Nb: 0.01% to 0.03%, N≤0.0060%, H≤0.0002%, O≤0.0012%, and the rest is Fe and unavoidable impurities.

[0011] The metallographic structure of the hot-rolled pickled steel plate of the present invention is bainite + a small amount of martensite, and the yield strength R of the hot-rolled pickled steel plate with a thickness of 2.5 to 4.5 mm is P0.2 1200~1400MPa, tensile strength R m 1800~2000MPa, elongation after fracture A 50mm The strength-ductility product is 11% to 16%, and the strength-ductility product is 22 to 29 GPa·%. The banded structure level of the hot-rolled pickled steel plate is ≤3.0B. According to the American Society for Testing and Materials "ASTM E45-13 Standard Test Method for Determination of Inclusion Content in Steel", method A is used for inspection, and the level of non-metallic inclusions in the hot-rolled pickled steel plate is ≤1.5.

[0012] The hardness of the saw back of the bimetallic band saw made of the hot-rolled pickled steel plate of the present invention after conventional quenching + tempering heat treatment is 52-56HRC.

[0013] The reasons why the chemical composition of the hot-rolled pickled steel sheet of the present invention is limited to the above range are as follows:

[0014] Carbon: It is the main alloying element in steel and the main element for the transformation of bainite and martensite. It directly affects the strength, plasticity, toughness and welding performance of steel. Although a higher C content is beneficial to strength and hardness, it is very detrimental to the plasticity and toughness of the band saw. With a lower C content, it is easy to obtain low-carbon lath martensite after heat treatment, which has better plasticity and toughness. The reduction in hardness caused by the reduction in carbon content can be achieved by adding a certain amount of alloying elements. After comprehensive consideration, the present invention sets the carbon content to 0.28% to 0.33%.

[0015] Silicon: As a solid solution strengthening element, it has a certain strengthening effect when dissolved in the steel coil matrix. At the same time, it acts as a deoxidizer during smelting, playing a role in deoxidation and desulfurization. However, when it is contained in large quantities, it will harden the material and significantly reduce the processing performance. In addition, Si promotes the formation of iron oxide scale on the surface of the steel coil during the hot rolling process, affecting the appearance of the finished product. After comprehensive consideration, the present invention sets the Si content to 0.20% to 0.40%.

[0016] Manganese: It is a good deoxidizer and desulfurizer. A certain amount of manganese in steel can eliminate or improve the hot working performance of steel, and at the same time can significantly improve the hardenability. However, when the content is too much, it will cause component segregation, resulting in uneven organization and large heat treatment deformation. After comprehensive consideration, the present invention sets the Mn content to 0.90% to 1.10%.

[0017] Chromium: It can significantly improve the hardenability of steel, and the effect is better when used in combination with manganese. It is also a strong carbide-forming element and can form a variety of alloy carbides. It also inhibits the grain size of the structure during the cooling process after hot rolling, and improves the strength and hardness of the material. Chromium can also improve the wear resistance of tool steel and has good tempering stability. However, too much content will increase the alloy cost. After comprehensive consideration, the present invention sets the Cr content to 3.8% to 4.0%.

[0018] Molybdenum: It can improve the hardenability and high temperature strength of steel and prevent temper brittleness. Molybdenum can also reduce the tendency of carbides to form a continuous network on the grain boundary in the carburized layer, reduce the residual austenite in the carburized layer, and relatively increase the wear resistance of the surface layer. Molybdenum itself is a precious metal. Too much content will greatly increase the cost. It is generally above 1.0% in tool steel. After comprehensive consideration, the present invention sets the Mo content to 1.2% to 1.4%.

[0019] Nickel: It is very close to the iron lattice and can form a continuous solid solution. It is beneficial to improve the hardenability and hardenability of steel. Nickel can stabilize austenite, increase the content of residual austenite during quenching, and improve quenching toughness. Nickel combined with chromium and molybdenum has better hardenability and a very high fatigue limit. Nickel itself is a precious metal, and excessive content will greatly increase the cost. After comprehensive consideration, the present invention sets the Ni content to 0.6% to 0.8%.

[0020] Vanadium: It exists in the form of carbides in steel, mainly to refine the structure and grain of steel and improve the welding performance of steel. Vanadium also increases tempering stability and wear resistance, thereby extending the service life of tools. However, vanadium itself is also a precious metal, and excessive content will greatly increase the cost, generally not more than 0.5%. After comprehensive consideration, the present invention sets the V content to 0.3% to 0.4%.

[0021] Aluminum: It mainly plays the role of deoxidation and binding free nitrogen in steel. Aluminum is a strong oxidizing element. It forms Al2O3 with oxygen in steel and is removed during steelmaking. At the same time, aluminum also has the effect of refining grains and preventing the coarsening of austenite grains. The presence of Al in chromium-molybdenum steel and chromium steel can increase its wear resistance. However, the disadvantage of aluminum is that it affects the welding performance and cutting performance of steel; at the same time, too much aluminum will form too many Al2O3 inclusions, which are easy to block the pouring nozzle during continuous casting. After comprehensive consideration, the present invention sets the Al content to 0.05% to 0.08%.

[0022] Niobium: solid solution in steel can significantly improve the hardenability of steel. Niobium has the effect of refining grains and significantly improves the strength of materials. Trace amounts of niobium can improve the strength without affecting the plasticity and toughness of steel, and can also improve the impact toughness and fatigue properties of steel and avoid temper brittleness. The present invention sets the Nb content to 0.01% to 0.03%.

[0023] Phosphorus: It is an impurity element. It segregates at the grain boundary, which reduces the processing performance, impact toughness, fatigue performance, and welding performance. It is hoped that its content can be reduced as much as possible, but considering the controllability of process equipment and dephosphorization cost, the present invention limits P to ≤ 0.015%.

[0024] Sulfur: It is an impurity element and exists in the form of FeS, MnS, etc. in steel to form low melting point compounds. When cutting at high speed with a band saw, it is easy to cause high temperature brittleness and cracks, so it is hoped to reduce its content as much as possible; considering the actual control ability and desulfurization cost, the present invention limits S to ≤ 0.003%.

[0025] Nitrogen: It is a strengthening element. As the nitrogen content in steel increases, the strength increases significantly, but the plasticity, especially the toughness, decreases significantly, the weldability deteriorates, and the hot brittleness of the material increases. Therefore, the present invention limits N≤0.0060%, which is also the advantage of the converter smelting process over the electric furnace smelting process.

[0026] Hydrogen: It has very low solubility in solid steel. It dissolves into the molten steel at high temperature and does not have time to escape when cooling. It accumulates in the structure to form high-pressure fine pores, which sharply reduce the plasticity, toughness and fatigue strength of the steel. In severe cases, it will cause cracks and brittle fractures in the slab. It is hoped that its content can be reduced as much as possible. At present, under the refining conditions of RH treatment, H is limited to 0.0002%.

[0027] Oxygen: It is a harmful element in steel. It mainly exists in the form of FeO, MnO, SiO2, Al2O3, CaO and other inclusions in steel, which reduces the strength and plasticity of steel; especially has a serious impact on fatigue strength and impact toughness. Therefore, it is hoped to reduce it as much as possible, but it is impossible to eliminate it completely, which will lead to a significant increase in manufacturing costs. Considering the actual control ability of the refining process, the present invention limits O to ≤ 0.0012%.

[0028] A method for manufacturing a high-strength and tough hot-rolled pickled steel plate for a bimetallic band saw back, the method comprising:

[0029] After the molten steel is refined in the LF ladle furnace and vacuum degassed in the RH furnace, it is continuously poured to obtain the continuous casting slab. During continuous casting, the superheat of the molten steel in the tundish is controlled to be ≤20℃; the slab solidification end is controlled by light pressure reduction; the inclusion level in the continuous casting slab is controlled according to the American Society for Testing and Materials (ASTM E45-13 Standard Test Method for Determination of Inclusion Content in Steel", Method A is used for inspection, and the non-metallic inclusion level in the continuous casting slab is ≤1.5 level; the chemical composition weight percentage of the continuous casting slab is: C: 0.28%~0.33%, Si: 0.20%~0.40%, Mn: 0.90%~1.10%, P≤0.015%, S≤0.003%, Cr: 3.8%~4.0%, Mo: 1.2%-1.4%, Ni: 0.6%-0.8%, V: 0.3%-0.4%, Al: 0.05%~0.08%, Nb: 0.01%~0.03%, N≤0.0060%, H≤0.0002%, O≤0.0012%, and the rest is Fe and unavoidable impurities;

[0030] The continuous casting slab is heated in a heating furnace and then hot rolled. The continuous casting slab is fed into the heating furnace by hot charging and hot delivery. The temperature of the continuous casting slab into the heating furnace is ≥400°C. The heating temperature of the continuous casting slab is 1220-1260°C, and the heating time is 210-270min. The hot rolling is a two-stage rolling process. The rough rolling is 6 passes of continuous rolling, which is rolled above the austenite recrystallization temperature. The rough rolling end temperature is 1040-1080°C. The finishing rolling is 7 passes of continuous rolling, the finishing temperature of the finishing rolling is 900-940°C, and the finishing rolling reduction rate is 88%-93%. After finishing rolling, the thickness of the steel plate is controlled to be 2.5-4.5mm. The laminar cooling adopts the rear cooling, the cooling rate is <15°C / S, and the coiling temperature is 660-700°C to obtain the hot-rolled steel coil.

[0031] The hot rolled steel coil is slowly cooled after coiling, and the cooling rate of the hot rolled steel coil to 100°C is 5-8°C / h;

[0032] After the hot rolled steel coil is unrolled, it is subjected to push-pull pickling, rinsing and coiling to obtain the finished hot rolled pickled steel plate. The push-pull pickling adopts hydrochloric acid pickling solution, the pickling temperature is 75-90°C, and the pickling time is 150-270s.

[0033] The hot rolling process and the hot rolled coil structure control are one of the key technical points to realize the present invention. Through calculation, the composition system A3 of the present invention is 788.9℃, and A1 is 773.3℃; the hot rolling processes adopted are all based on the composition system of the present invention and the calculated phase transition point.

[0034] The reasons for the production process system adopted by the present invention are as follows:

[0035] 1. The molten steel adopts the LF ladle furnace refining + RH furnace double refining process and the setting of continuous casting process

[0036] Controlling non-metallic inclusions in molten steel is a key technology for realizing the present invention, because the oxygen content in steel and the size and shape of non-metallic inclusions have a great influence on the fatigue performance of the bimetallic band saw during use. Excessive size and excessive number of inclusions will cause microcracks or even cracks in the band saw, resulting in product failure.

[0037] Therefore, the molten steel of the present invention adopts a double refining process of LF ladle furnace refining + RH furnace vacuum degassing to ensure that the non-metallic inclusion level in the finished steel coil is controlled below level 1.5, and [N]≤0.0060%, [O]≤0.0012%, [H]≤0.0002%, meeting the toughness and fatigue performance requirements of the bimetallic band saw. At the same time, too high H content will also cause longitudinal cracks in the slab and micro cracks in the steel coil.

[0038] During continuous casting, the superheat of molten steel in the tundish is controlled to be ≤20℃; light pressure is used to control the end of slab solidification to improve the uniformity of slab structure; the level of non-metallic inclusions in the continuous casting slab is controlled to be ≤1.5.

[0039] 2. Setting of heating temperature and heating time for continuous casting slab

[0040] The steel alloy content of the saw back of the bimetallic band saw is high. Rapid heating from a cold state will produce certain thermal stresses, causing the slab to deform or crack. Therefore, it is usually required that the continuous casting slab be cut and then put into the furnace in a hot state. The continuous casting slab is put into the heating furnace by hot charging and hot delivery. The temperature of the continuous casting slab entering the heating furnace is ≥400℃. The setting of the heating temperature and time of the continuous casting slab is to ensure that the alloy elements such as C, Mn, Cr, Mo, Ni, and V in the continuous casting slab are fully diffused and dissolved, and the coarse carbide particles are dissolved and evenly distributed in the steel. Too low temperature and too short heating time cannot achieve the above purpose. The present invention should adopt a higher slab heating temperature, with a target temperature of 1240℃. If the temperature is too high and the heating time is too long, the slab surface will be severely oxidized, which is not conducive to the final performance and surface quality of the steel coil, and also consumes energy. Therefore, the present invention sets the continuous casting slab heating temperature to 1220℃~1260℃ and the heating time to 210~270min.

[0041] 3. Setting of finishing temperature

[0042] The finishing temperature setting of the present invention has two effects. On the one hand, by rolling the material in the austenite non-recrystallization zone, flat austenite grains with deformation bands inside are obtained, which are transformed into fine grains in the subsequent laminar cooling process, which plays a role in refining the structure and reducing band segregation; on the other hand, if the final rolling temperature is too low, it will cause excessive rolling load and affect rolling stability. Therefore, the present invention sets the finishing temperature of 900-940°C.

[0043] 4. Setting of laminar cooling mode and cooling speed

[0044] The laminar cooling after finishing rolling of the present invention adopts a different post-cooling process from the conventional one, so as to prevent the austenite structure in the material after finishing rolling from cooling too fast and reduce the occurrence of martensite structure transformation, so the cooling rate is set to be less than 15°C / S.

[0045] 5. Setting of hot rolling coiling temperature

[0046] The hot rolling coiling temperature mainly affects the structure, performance and subsequent spheroidizing annealing effect of the material. Under certain conditions, the grains should be as fine and uniform as possible, which is conducive to the subsequent unwinding process. If the coiling temperature is too high, the grains will be coarse and the structure will be uneven. If the coiling temperature is too low, the strength of the hot rolled material will increase significantly, the brittleness of the steel coil will increase, and it will be unfavorable for further unwinding and pickling. Therefore, the present invention sets the hot rolling coiling temperature to 660-700°C.

[0047] 6. Setting of slow cooling speed of hot rolled steel coil

[0048] The hot-rolled steel coil needs to be cooled slowly after coiling, mainly to prevent local air cooling of the steel coil after coiling. Too fast cooling rate will cause more martensitic transformation, which will significantly increase the brittleness of the material, cause local cracking and broken strip problems, and affect the subsequent opening and pickling processing; the cooling rate of the hot-rolled steel coil to 100°C is set at 5-8°C / h.

[0049] 7. Pickling process setting

[0050] Since this product has a high Cr content and uses a high furnace temperature, there is a thick chromium-containing alloy oxide layer below the surface iron oxide scale, and the oxide layer is dense, making pickling very difficult. In addition, this type of oxide gathers on the grain boundaries and penetrates into the internal tissue, affecting the subsequent heat treatment effect of the material. Therefore, a reasonable pickling process can not only efficiently clean the surface iron oxide scale and alloy oxides, but also reduce the internal oxidation of the surface tissue, improve the surface quality of the material and ensure the subsequent heat treatment performance. Through experimental optimization, a longer pickling time and a higher temperature are required. The present invention sets the push-pull pickling hydrochloric acid pickling temperature to 75-90°C and the pickling time to 150-270s.

[0051] The metallographic structure of the hot-rolled pickled steel plate obtained by the present invention is bainite + a small amount of martensite, and the yield strength R of the hot-rolled pickled steel plate with a thickness of 2.5 to 4.5 mm is P0.2 1200~1400MPa, tensile strength R m 1800~2000MPa, elongation after fracture A 50mm The strength-ductility product is 11% to 16%, and the strength-ductility product is 22 to 29 GPa·%; the banded structure level of the hot-rolled pickled steel plate is ≤3.0B; the level of non-metallic inclusions in the hot-rolled pickled steel plate is ≤1.5.

[0052] The hardness of the saw back of the bimetallic band saw made of the hot-rolled pickled steel plate produced by the method of the present invention after conventional quenching + tempering heat treatment is 52-56HRC.

[0053] Compared with the prior art, the present invention has the following positive effects: 1. The hot-rolled pickled steel plate of the present invention adopts a composition design method of appropriately reducing the carbon content, effectively adding a certain amount of alloy elements such as Cr, Mo, V, Nb, etc., adopting LF+RH double refining, and strictly controlling the harmful elements P, S, N, O, and H in the steel to reduce non-metallic inclusions, improve the purity of steel, and improve the quenching hardness and fatigue performance of the finished material. 2. The production process of the hot-rolled pickled steel plate continuous casting slab of the present invention improves the organization of the material by controlling the superheat of the molten steel, the light pressing process of the slab, and combining the hot rolling process to regulate the microstructure of the material, so that the banded structure level of the hot-rolled pickled steel plate is controlled below 3.0B; the processing toughness of the hot-rolled pickled steel plate is improved. 3. The method of the present invention maintains high strength and high toughness while refining the structure through matching process design of slab heating process, hot rolling process temperature and slow cooling process, so that high-strength hot-rolled steel coil can be directly unrolled and pickled without annealing; and the surface quality after pickling is higher than that of annealed steel coil, and there is no strip breakage during the pickling process; compared with the existing technology, the softening annealing process before pickling is reduced, and the manufacturing cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a photograph of the internal metallographic structure of the hot-rolled pickled steel plate in Example 3 of the present invention, and its magnification is 500 times.

[0055] Figure 2 This is a scanning electron microscope (SEM) photograph of the surface microstructure of the hot-rolled pickled steel plate of Example 3 of the present invention, and the magnification is 1000 times. DETAILED DESCRIPTION

[0056] The present invention is further described below in conjunction with Examples 1 to 6, as shown in Tables 1 to 5.

[0057] Table 1 shows the chemical composition (by weight percentage) of the steel according to the embodiment of the present invention, with the remainder being Fe and unavoidable impurities.

[0058] Table 1 Chemical composition of steel according to the embodiment of the present invention, unit: weight percentage, %.

[0059]

[0060]

[0061] Table 1 Chemical composition of the steel of the embodiment of the present invention, unit: weight percentage, %.

[0062] element Al Nb N H O The present invention 0.05-0.08 0.01-0.03 ≤0.0060 ≤0.0002 ≤0.0012 Example 1 0.053 0.023 0.0053 0.0002 0.0011 Example 2 0.076 0.028 0.0042 0.0002 0.0009 Example 3 0.068 0.014 0.0047 0.0001 0.0011 Example 4 0.056 0.027 0.0055 0.0001 0.0010 Example 5 0.064 0.018 0.0050 0.0002 0.0008 Example 6 0.071 0.021 0.0048 0.0001 0.0007

[0063] Molten steel that meets the chemical composition requirements is obtained through converter smelting, deep desulfurization and alloy composition fine-tuning in LF ladle refining furnace, and then vacuum cycle degassing treatment in RH furnace; finally, continuous casting slabs are cast by continuous casting machine.

[0064] The continuous casting slab is directly sent to the heating furnace for heating. The continuous casting slab is sent to the heating furnace by hot charging and hot delivery. The continuous casting slab is heated in the heating furnace and then hot rolled. The hot rolling is a two-stage rolling process. The rough rolling and finishing rolling units are used to implement controlled rolling. After laminar cooling, the laminar cooling adopts the rear cooling method. After slow cooling in the slow cooling wall, the hot rolled steel coil is produced. The thickness of the hot rolled steel coil is 2.5-4.5 mm. The hot rolling process control parameters are shown in Table 2.

[0065] Table 2 Hot rolling process parameters of the embodiment of the present invention

[0066]

[0067] After the hot rolled steel coil is coiled, it enters the slow cooling hood for slow cooling. The cooling rate of the hot rolled steel coil to 100°C is 5 to 8°C / h.

[0068] The hot rolled steel coil after slow cooling is unrolled on the unwinding machine and then straightened and pickled to obtain the finished hot rolled pickled steel plate. The push-pull pickling adopts hydrochloric acid pickling solution, the pickling temperature is 75-90°C, and the pickling time is 150-270s. The pickling process used in the embodiment of the present invention is shown in Table 3.

[0069] Table 3 Pickling process adopted in the embodiment of the present invention

[0070] Hot rolling parameters Hot rolled pickled steel plate thickness / mm Pickling temperature / ℃ Pickling time / S The present invention 2.8-4.5 75-90 150-270 Example 1 3.0 80 205 Example 2 4.0 85 250 Example 3 4.5 88 195 Example 4 2.8 75 175 Example 5 3.5 85 230 Example 6 2.6 78 170

[0071] The hot-rolled pickled steel sheet obtained by the above method is shown in Figure 1 The metallographic structure of hot-rolled pickled steel plate is bainite + a small amount of martensite. The yield strength R of 2.5-4.5mm thick hot-rolled pickled steel plate is P0.21200~1400MPa, tensile strength R m 1800~2000MPa, elongation after fracture A 50mm The strength-ductility product is 11% to 16%, and the strength-ductility product is 22 to 29 GPa·%; the banded structure level of the hot-rolled pickled steel plate is ≤3.0B; the level of non-metallic inclusions in the hot-rolled pickled steel plate is ≤1.5.

[0072] The hot-rolled pickled steel plate obtained by the present invention is subjected to a tensile test according to "GB / T228.1-2010 Tensile test of metal materials Part 1: Room temperature test method"; the surface hardness of the steel plate is tested according to "GB / T 230-2009 Metal Rockwell hardness test method"; the microstructure and banded structure level are tested according to "GB / T 13299 Steel microstructure evaluation method";

[0073] "ASTM E45-13 Standard Test Method for Determination of Inclusion Content in Steel" adopts Method A for inclusion rating; the performance parameters of hot-rolled pickled steel plates are shown in Table 4; the internal quality indicators of hot-rolled pickled steel plates are shown in Table 5.

[0074] Table 4 Performance indexes of hot-rolled pickled steel coils according to the present invention

[0075]

[0076] Table 5 Internal quality indexes of hot-rolled pickled steel coils according to the present invention

[0077]

[0078] The hot-rolled pickled steel plate obtained by the present invention has a medium carbon content and a large amount of alloy elements, and the carbides are finely and evenly distributed; the material has high strength and high toughness; there is no broken strip during the uncoiling and pickling process; see Figure 2 After pickling, the surface quality is good and there is no iron oxide residue.

[0079] The saw back of the bimetallic band saw made from the hot-rolled pickled steel plate produced by the method of the present invention was subjected to conventional quenching + tempering heat treatment. The hardness of the saw back of the bimetallic band saw made from the hot-rolled pickled steel plate of Examples 1-6 after quenching + tempering heat treatment was 52.5HRC, 53.8HRC, 53.0HRC, 54.5HRC, 54.2HRC, and 55.7HRC, respectively.

[0080] The hot-rolled pickled steel plate of the present invention meets the user's requirements for high hardness and high toughness as a backing material for a bimetallic band saw.

[0081] In addition to the above embodiments, the present invention may also have other implementation modes; any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. A high-strength and tough hot-rolled pickled steel plate for a bimetallic band saw back, the chemical composition weight percentage of which is: C: 0.28% to 0.33%, Si: 0.20% to 0.40%, Mn: 0.90% to 1.10%, P≤0.015%, S≤0.003%, Cr: 3.8% to 4.0%, Mo: 1.2%-1.4%, Ni: 0.6%-0.8%, V: 0.3%-0.4%, Al: 0.05% to 0.08%, Nb: 0.01% to 0.03%, N≤0.00 60%, H≤0.0002%, O≤0.0012%, the rest are Fe and unavoidable impurities; the metallographic structure of hot-rolled pickled steel plate is bainite + a small amount of martensite; the strength-ductility product of 2.5-4.5mm thick hot-rolled pickled steel plate is 22-29GPa·%; the banded structure level of hot-rolled pickled steel plate is ≤3.0B; according to the American Society for Testing and Materials "ASTME45-13 Standard Test Method for Determination of Inclusion Content in Steel", method A is used to inspect inclusions in steel plates, and the level of non-metallic inclusions in hot-rolled pickled steel plates is ≤1.

5.

2. The high-strength and toughness hot-rolled pickled steel plate for the saw back of a bimetallic band saw as claimed in claim 1, characterized in that: Yield strength R of 2.5-4.5mm thick hot-rolled pickled steel plate P0.2 1200~1400MPa, tensile strength R m 1800~2000MPa, elongation after fracture A 50mm It is 11% to 16%.

3. The high-strength and toughness hot-rolled pickled steel plate for the saw back of a bimetallic band saw as claimed in claim 1, characterized in that: The hardness of the saw back of the bimetallic band saw made of the hot-rolled pickled steel plate after quenching and tempering heat treatment is 52-56HRC.

4. The method for manufacturing a high-strength and tough hot-rolled pickled steel plate for a bimetallic band saw back according to claim 1, characterized in that: The following steps are involved: After the molten steel is refined in the LF ladle furnace and vacuum degassing is carried out in the RH furnace, it is continuously poured to obtain the continuous casting slab. During continuous casting, the superheat of the molten steel in the tundish is controlled to be ≤20°C; the slab solidification end is controlled by light pressure reduction; the inclusion level in the continuous casting slab is controlled, and the non-metallic inclusion level in the continuous casting slab is ≤1.5 according to the American Society for Testing and Materials "ASTME45-13 Standard Test Method for Determining the Content of Inclusions in Steel", and the method A is used for inspection. The chemical composition weight percentage of the continuous casting slab is: C: 0.28% to 0.33% , Si: 0.20% ~ 0.40%, Mn: 0.90% ~ 1.10%, P ≤ 0.015%, S ≤ 0.003%, Cr: 3.8% ~ 4.0%, Mo: 1.2% -1.4%, Ni: 0.6% -0.8%, V: 0.3% -0.4%, Al: 0.05% ~ 0.08%, Nb: 0.01% ~ 0.03%, N ≤ 0.0060%, H ≤ 0.0002%, O ≤ 0.0012%, the rest is Fe and unavoidable impurities; The continuous casting slab is heated in a heating furnace and then hot rolled. The continuous casting slab is fed into the heating furnace by hot charging and hot delivery. The temperature of the continuous casting slab into the heating furnace is ≥400°C. The heating temperature of the continuous casting slab is 1220-1260°C, and the heating time is 210-270min. The hot rolling is a two-stage rolling process. The rough rolling is 6 passes of continuous rolling, which is rolled above the austenite recrystallization temperature. The rough rolling end temperature is 1040-1080°C. The finishing rolling is 7 passes of continuous rolling, the finishing temperature of the finishing rolling is 900-940°C, and the finishing rolling reduction rate is 88%-93%. After finishing rolling, the thickness of the steel plate is controlled to be 2.5-4.5mm. The laminar cooling adopts the rear cooling, the cooling rate is <15°C / S, and the coiling temperature is 660-700°C to obtain the hot-rolled steel coil. The hot rolled steel coil is slowly cooled after coiling, and the cooling rate of the hot rolled steel coil to 100°C is 5-8°C / h; After the hot-rolled steel coil is unrolled, it is subjected to push-pull pickling, rinsing, and coiling to obtain a finished hot-rolled pickled steel plate. The push-pull pickling uses hydrochloric acid pickling solution, the pickling temperature is 75-90° C., and the pickling time is 150-270s.

5. The manufacturing method according to claim 4, characterized in that: Yield strength R of 2.5-4.5mm thick hot-rolled pickled steel plate P0.2 1200~1400MPa, tensile strength R m 1800~2000MPa, elongation after fracture A 50mm It is 11% to 16%.

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