Method for smelting steel for laser welding welding wire of aluminum-based or aluminum-silicon-based coated hot stamping steel

Abstract

The present invention belongs to the technical field of welding materials, and provides a smelting method for aluminum-based or aluminum-silicon-based coated hot stamping steel laser welding wire. The welding wire steel is composed of the following chemical components in weight percentage: C: 0.01%~0.30%, Si: 0.6%~1.3%, Mn: 1.6%~2.8%, S: 0.008%~0.018%; Cr: 0.4%~3.0%, Mo: 0.5%~2.0%, Ni: 1.6%~4.0%, Zr+Ti+Nb: 0.05%~0.1%, RE: 0~0.02%, P≤0.010%, Al≤0.005%, and the remainder is Fe and unavoidable impurities. The smelting method includes an electric furnace smelting process, an LF furnace refining process, a vacuum treatment process, and a billet continuous casting process. The welding wire steel can effectively overcome the problem of brittle fracture caused by the high content of Al element dissolving into the weld during laser welding.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and relates to a method for smelting steel for aluminum-based or aluminum-silicon-based coated hot stamping steel laser welding wire. Background Art

[0002] Ultra-high strength and toughness automotive steel is one of the most economical and effective solutions for lightweighting vehicles, and is of great significance in alleviating the dual carbon reduction pressure from the manufacturing and application ends. Among them, aluminum-silicon coated hot stamping steel is gaining more and more attention because it has higher strength after die quenching.

[0003] The integrated forming technology of hot stamping steel with multi-part integration has developed rapidly, and the laser welding of hot stamping steel with aluminum-silicon coating of different thicknesses and strength grades has become the key. As a common welding method, laser welding is widely used in car body manufacturing. Its advantages are: improving collision performance, achieving smoother force conduction through continuous butt welding; reducing car body weight, using advanced hot forming materials to improve material strength and reduce structural thickness; saving costs, laser welding optimizes material utilization and reduces waste. The use of unequal thickness laser welded plates in car body manufacturing can reduce car body weight, reduce the number of parts, improve safety and reliability, and reduce costs. With the rapid development of integrated forming technology of hot stamping steel with multi-part integration, the laser welding of hot stamping steel with aluminum-silicon coating of different thicknesses and strength grades has become the key. However, the aluminum-silicon coating contains a high content of Al elements, which easily enters the weld during laser welding and causes brittle fracture. In the existing laser welding scheme for hot stamped steel with aluminum-based or aluminum-silicon-based coatings, laser ablation of the aluminum-silicon coating and then laser welding can be used. This method has complicated procedures and high costs. Alternatively, a large amount of welding wire can be filled by controlling the gap between the sheets. The disadvantage of this method is that the alloy content of the filled welding wire is extremely high, which increases the cost. At the same time, the composition of the weld formed in the gap between the sheets is different from that of the sheets on both sides, which greatly increases the probability of weld failure and reduces the yield rate.

[0004] At present, it is necessary to develop a special welding wire steel for laser welding of aluminum-based or aluminum-silicon-based coated hot stamping steel to overcome the problem of brittle fracture caused by the high content of Al element dissolving into the weld during laser welding. Therefore, developing a welding wire steel suitable for laser welding of aluminum-based or aluminum-silicon-based coated hot stamping steel has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] In view of this, the present invention proposes a method for smelting steel for laser welding welding wire of aluminum-based or aluminum-silicon-based coated hot stamping steel.

[0006] In order to solve at least one of the above technical problems, the present invention adopts the following technical solution:

[0007] According to the present invention, a smelting method for aluminum-based or aluminum-silicon-based coated hot stamping steel laser welding wire is provided. The welding wire steel is composed of the following chemical components in weight percentage: C: 0.01%~0.30%, Si: 0.6%~1.3%, Mn: 1.6%~2.8%, S: 0.008%~0.018%; Cr: 0.4%~3.0%, Mo: 0.5%~2.0%, Ni: 1.6%~4.0%, Zr+Ti+Nb: 0.05%~0.1%, RE: 0~0.02%, P≤0.010%, Al≤0.005%, and the balance is Fe and unavoidable impurities. The smelting method comprises the following steps: an electric furnace smelting process: smelting is performed using clean scrap steel as a charge, and alloying of Ni is completed in the electric furnace, wherein P≤0.030%, S≤0.020% in the clean scrap steel, and the remaining alloy contents meet the limitations of the chemical composition of steel for welding wire; an LF furnace refining process: desulfurizing the molten steel, alloying the non-easy-to-burn elements, and controlling the composition of the ladle slag; a vacuum treatment process: alloying the molten steel with rare earths and easy-to-burn elements, degassing, and removing inclusions; and a billet continuous casting process: full-process protection casting.

[0008] According to one embodiment of the present invention, Zr+Ti+Nb is any one of Zr+Ti+Nb, Zr+Nb, Zr+Ti, Ti, and Ti+Nb; RE is one or more of La, Ce, and Y elements.

[0009] According to one embodiment of the present invention, in the electric furnace smelting process, the endpoint carbon is controlled to be ≤0.05%, the endpoint phosphorus is controlled to be ≤0.008%, and the endpoint temperature is controlled to be ≥1660°C.

[0010] According to one embodiment of the present invention, in the electric furnace smelting process, argon is blown throughout the steel tapping process, and a calcium-based slag modifier is added to the slag surface after the steel tapping is completed.

[0011] According to one embodiment of the present invention, in the electric furnace smelting process, lime is mixed and added at a ratio of 4-6 kg / ton of steel after 2 / 3 of the steel is tapped.

[0012] According to one embodiment of the present invention, when smelting steel for welding wire with C>0.06%, low aluminum silicon calcium barium deoxidation is adopted after 1 / 3 of the steel is tapped, and the oxygen is fixed to an oxygen activity of ≤20ppm after the furnace; after the steel is tapped, a calcium-based steel slag modifier is added to the slag surface at a ratio of 3-5kg / ton of steel.

[0013] According to one embodiment of the present invention, when smelting steel for welding wire with C ≤ 0.06%, a calcium-based steel slag modifier is added to the slag surface at a ratio of 1-3 kg / ton of steel after steel tapping is completed; the C content is reduced to less than 0.002% through a vacuum decarburization process; after decarburization, a calcium-based steel slag modifier is added to the slag surface at a ratio of 1-3 kg / ton of steel; after argon blowing and stirring, the slag enters the LF furnace, and low-aluminum silicon calcium barium deoxidation is used to adjust the oxygen to an oxygen activity of ≤ 20 ppm.

[0014] According to one embodiment of the present invention, in the LF furnace refining process, the ladle slag composition is controlled to meet the following requirements: in weight ratio, CaO / SiO2=1.1~1.6; in weight percentage, (FeO+MnO)≤1.0%, Al2O3: 3%~6%, MgO: 4%~7%.

[0015] According to one embodiment of the present invention, in the vacuum treatment process, the vacuum degree is controlled to be ≤3mbar, the treatment time is 20-25min, the circulation time after alloying of the easily burnt elements is ≥10min, and the station is exited after soft argon blowing for 25-35min after breaking the air.

[0016] According to one embodiment of the present invention, for a 200 mm×200 mm billet, the superheat is controlled to be 20-25° C., and the reduction is controlled to be 3-5 mm.

[0017] By adopting the above technical solution, the present invention has at least one of the following advantages compared with the prior art:

[0018] (1) The present invention smelts welding wire steel suitable for laser welding of aluminum-based or aluminum-silicon-based coated hot stamping steel by means of raw material control, electric furnace smelting process control, refining slag making system, vacuum degassing, continuous casting protection pouring and other measures. The welding wire steel support welding wire prepared by the method of the present invention is used to fill the laser welding weld, which can make the maximum strength of the weld higher than 2200MPa, thereby effectively ensuring that the tensile failure position of the welded part of the 2200MPa strength aluminum-silicon coated hot stamping steel is the base material area.

[0019] (2) The present invention improves the cleanliness of molten steel by controlling the composition of ladle slag and the corresponding refining process, reduces wire breakage caused by inclusions in the subsequent drawing process of welding wire, and improves the quality of the weld.

[0020] (3) The present invention adopts a continuous casting process, which can significantly improve the yield rate and reduce the cost compared with the die casting process generally used for high alloy content welding wire steel.

[0021] (4) The present invention uses different process flows for welding wire steels with different carbon contents: welding wire steels with a carbon content of ≤0.06% adopt a process flow of electric furnace-vacuum-electric heating (LF)-vacuum-continuous casting; welding wire steels with a higher carbon content of >0.06% adopt a process flow of electric furnace-electric heating (LF)-vacuum-continuous casting, thereby ensuring that welding wire steels with different compositions have good comprehensive properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A flow chart of a method for smelting steel for laser welding wire of aluminum-based or aluminum-silicon-based coated hot stamping steel provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0025] It should be understood that the embodiments of the present invention shown in the exemplary embodiments are only illustrative. Although only a few embodiments are described in detail in the present invention, it is easy for those skilled in the art to appreciate that multiple modifications are feasible without actually departing from the teaching of the subject matter of the present invention. Accordingly, all such modifications should be included within the scope of the present invention. Without departing from the gist of the present invention, other replacements, modifications, changes and deletions may be made to the design, operating conditions and parameters of the following exemplary embodiments.

[0026] According to an embodiment of the present invention, a smelting method for aluminum-based or aluminum-silicon-based coated hot stamping steel laser welding wire is provided. The welding wire steel smelted by the method can be composed of the following chemical components in weight percentage: C: 0.01%~0.30%, Si: 0.6%~1.3%, Mn: 1.6%~2.8%, S: 0.008%~0.018%; Cr: 0.4%~3.0%, Mo: 0.5%~2.0%, Ni: 1.6%~4.0%, Zr+Ti+Nb: 0.05%~0.1%, RE: 0~0.02%, P≤0.010%, Al≤0.005%, and the balance is Fe and unavoidable impurities.

[0027] Carbon (C): It is the most economical and effective strengthening element often added to most high-strength steels or ultra-high-strength steels. C stabilizes the austenite phase through interstitial solid solution strengthening, reduces the Ac3 phase transformation point, and reduces the austenitization temperature accordingly. When the C content is higher than 0.3%, the martensitic phase transformation mechanism will change from dislocation martensite to a mixed structure of dislocation and twin martensite, with brittle twin martensite accounting for 5% to 10%, which is extremely unfavorable for toughness. For this reason, the present invention sets the upper limit of the C content of welding wire steel to 0.30% to ensure that the weld has a certain toughness and is not prone to brittle fracture.

[0028] Manganese (Mn): It is an important austenite stabilizing element, which can expand the austenite phase region, reduce the Ac3 temperature, and help reduce the Al content in the weld of the aluminum-silicon plate. Mn can also effectively inhibit the transformation of austenite to ferrite and enhance the hardenability of steel. However, too high a Mn content will have an adverse effect on the plasticity, toughness and welding performance of steel. Therefore, the content of Mn element should be controlled within a relatively reasonable range. Based on the experimental results, the present invention controls the Mn content to 1.6%~2.8%.

[0029] Nickel (Ni): An austenite-forming element that can effectively reduce the Al content in the weld of aluminum-silicon plate tailored welds, expand the austenite phase region, and effectively control the formation of high-temperature delta ferrite. Based on experimental results and cost factors, the Ni content is limited to 1.6%~4.0%.

[0030] Molybdenum (Mo): Adding it to steel can play a good role in strengthening grain boundaries, and at the same time has good wear resistance and corrosion resistance. Furthermore, Mo can also form strengthening phases and precipitates, playing a strengthening role. However, when the Mo element content is higher than 3%, the oxidation resistance will deteriorate. Therefore, the alloy composition of the steel for welding wire of the present invention limits the Mo content to 0.5%~2.0%.

[0031] Chromium (Cr): can improve the hardenability of steel, improve the strength and wear resistance of steel, and enhance the oxidation resistance of steel. The effect is increased when added together with Si element. The Cr content of the steel for welding wire of the present invention is limited to 0.4% to 3.0%.

[0032] Aluminum (Al): When the Al content is too high, Al2O3 inclusions will be generated, which is detrimental to the mechanical properties. Therefore, the Al content in the steel for welding wire of the present invention needs to be controlled within 0.005%.

[0033] Silicon (Si): used as deoxidation in the steelmaking process, and its content depends on the steelmaking process used. In addition, Si can inhibit the formation of cementite, stabilize the precipitation of ε or η transition carbides, and promote the partitioning of C into the residual austenite to increase the stability of austenite. However, too high Si content will deteriorate the plasticity and welding performance of steel. At the same time, the combination of Si and Cr can effectively improve the high-temperature oxidation resistance of the material. The alloy composition of the steel for the welding wire of the present invention limits the Si content to 0.6%~1.3%.

[0034] Niobium (Nb), titanium (Ti), zirconium (Zr): Titanium mainly plays the role of fixing C and N elements. Adding a small amount of niobium, zirconium and other elements has the effect of degassing, purifying and refining grains. In the embodiment of the present invention, Zr+Ti+Nb is one of Zr+Ti+Nb, Zr+Nb, Zr+Ti, Ti, and Ti+Nb. The nitride particles with a size of hundreds of nanometers precipitated during the high-temperature soaking process can effectively inhibit the growth of high-temperature austenite. When the Ti and N contents are high, TiN is easily precipitated in the liquid phase, and its particle size is generally at the level of ten microns, which is extremely unfavorable to the mechanical properties of steel. Therefore, when using Ti microalloying design, the addition amount of Ti and N elements should be strictly controlled to avoid the formation of larger-sized liquid TiN. Niobium can increase the grain coarsening temperature to play a role in refining grains. Zirconium is also a strong carbide-forming element, and has a strong affinity with gases such as oxygen and nitrogen, and can be used as a non-evaporable degassing agent. Adding a small amount of zirconium has the effect of degassing, purifying and refining grains. Niobium, titanium and zirconium work synergistically. Based on the experimental results, the content of Zr+Ti+Nb in the steel composition for the welding wire of the present invention is preferably limited to 0.05% to 0.1%.

[0035] Rare earth (RE): one or more elements such as La, Ce, and Y. The purification effect of rare earth in steel is mainly manifested in deeply reducing the harmful effects of low-melting-point elements such as sulfur, phosphorus, hydrogen, arsenic, tin, antimony, bismuth, and lead. At the same time, trace amounts of rare earth elements can also improve the high-temperature oxidation resistance of the material. The rare earth RE content is too high, the cost is high, and too high an addition amount will cause the water nozzle to be blocked during the continuous casting process. In the invention, rare earth is an optional element, and its content in the steel composition for welding wire is preferably limited to 0~0.02% to play a purifying role and improve the high-temperature oxidation resistance of the material.

[0036] Phosphorus (P) is considered a harmful element in steel. P tends to form microsegregation when the molten steel solidifies, which significantly increases the brittleness of the steel and greatly reduces the sensitivity to hydrogen-induced cracking. Therefore, it is preferred to control the P content to less than 0.010%.

[0037] like Figure 1 As shown, the smelting method of the above-mentioned aluminum-based or aluminum-silicon-based coated hot stamping steel welding wire may specifically include the following steps:

[0038] Step S101: an electric furnace smelting process, using clean scrap steel as a charge for smelting, and completing the alloying of Ni in the electric furnace, wherein P≤0.030%, S≤0.020% in the clean scrap steel, and the remaining alloy contents meet the chemical composition requirements of steel for welding wire;

[0039] Step S102: LF furnace refining process, desulfurizing the molten steel, alloying the non-burnable elements, and controlling the ladle slag composition;

[0040] Step S103: vacuum treatment process, alloying the molten steel with rare earth and easily burnable elements, degassing and removing inclusions;

[0041] Step S104: billet continuous casting process, with full protection of the casting.

[0042] Clean scrap steel refers to a product that separates impurities such as slag, soil, rubber and other non-metallic impurities and non-ferrous metals mixed in ordinary scrap steel, and cleans the oil stains attached to the surface of the scrap steel. Using clean scrap steel as a charge for smelting can not only solve the problem of scrap steel treatment and realize resource recycling; compared with directly using ordinary scrap steel as raw material, it can also achieve stable recovery and high recovery rate of metals, avoid bringing impurities in scrap steel into the steelmaking furnace to reduce the difficulty of steelmaking slag, and have better cost performance. In the embodiment of the present invention, P≤0.030%, S≤0.020% in the clean scrap steel, and the remaining alloy content meets the chemical composition of steel for welding wire. The specific yield is considered to be 98%, and is controlled according to the composition limit.

[0043] In the steelmaking process, end point carbon, end point phosphorus and end point temperature are important control parameters. Control of the end point carbon content is crucial to the structure and properties of steel. The end point phosphorus content needs to be controlled at a low level because phosphorus reduces the toughness and plasticity of steel and increases the cold brittleness of steel. The end point temperature also needs to be precisely controlled to ensure the quality of the molten steel and the subsequent smooth casting process. Too high a temperature may cause problems such as molten steel aspiration and aggravate element burnout; too low a temperature may deteriorate the fluidity of the molten steel and affect casting. In the electric furnace smelting process of step S101, it is preferably controlled to control the end point carbon ≤0.05%, the end point phosphorus ≤0.008%, and the end point temperature ≥1660℃.

[0044] During the steel-making process, lime can be mixed and added to the molten steel. Lime reacts with impurities such as phosphorus and sulfur in the molten steel at high temperature to form corresponding compounds, thereby reducing the content of these impurities in the molten steel and improving the quality of the steel. However, the amount of lime added to the steel-making process needs to be precisely controlled, and excessive or insufficient amounts may affect the smelting effect. In an embodiment of the present invention, lime is preferably mixed and added to the molten steel at a ratio of 4 to 6 kg / ton of steel after 2 / 3 of the steel is tapped. Furthermore, the electric furnace smelting process is argon-blown throughout the steel-making process, and a calcium-based slag modifier is added to the slag surface after the steel-making process is completed. The calcium-based slag modifier can be used to improve the performance of the slag, and it may contain the following components in weight percentage: CaC2: 40% to 70%, SiO2: 10% to 30%, CaO: 10% to 30%, CaF2: 8% to 15%, S≤0.2%, P≤0.1%, and the rest are unavoidable impurities. During the process of adding the modifier, argon is blown throughout the process, and the molten steel is not overturned, so that the modifier and the original ladle slag fully react and spread to the entire surface of the molten steel. In this way, the oxidizability of the ladle slag can be effectively reduced, the composition of the ladle slag can be optimized, and its inclusion adsorption capacity can be improved, while reducing production costs. The use of CaC2 as a deoxidizer will not only cause a certain degree of carbon increase, but also improve the foaming conditions due to the presence of CO products, which is beneficial to submerged arc operation, reduce equipment damage, reduce molten steel exposure, and reduce molten steel nitrogen absorption; at the same time, the calcium-based ladle top slag modifier is formulated with a certain amount of SiO2 to generate dicalcium silicate and tricalcium silicate with stable performance and gelling activity, thereby improving the stability of the modified steel slag.

[0045] In an embodiment of the present invention, in order to accurately control the final C content, different process flows are used for welding wire steels with different carbon contents: when smelting welding wire steel with C>0.06%, low aluminum silicon calcium barium deoxidation is adopted after 1 / 3 of the steel is tapped, and the oxygen is set to an oxygen activity of ≤20ppm after the furnace, and a calcium-based steel slag modifier is added to the slag surface at a ratio of 3-5kg / ton of steel after the steel is tapped; when smelting welding wire steel with C≤0.06%, a calcium-based steel slag modifier is added to the slag surface at a ratio of 1-3kg / ton of steel after the steel is tapped; the C content is reduced to less than 0.002% through a vacuum decarburization process; after decarburization, a calcium-based steel slag modifier is added to the slag surface at a ratio of 1-3kg / ton of steel; after argon blowing and stirring, it enters the LF furnace, and low aluminum silicon calcium barium deoxidation is adopted, and the oxygen activity is set to ≤20ppm.

[0046] In the LF furnace refining process of step S102, the molten steel is mainly desulfurized, the non-easy-to-burn elements are alloyed, and the ladle slag composition is controlled. Among them, the alloying treatment of non-easy-to-burn elements includes the alloying treatment of Nb, Cr, and Mo. LF furnace refining (LADLE FURNACE) is a ladle refining furnace, which is the main off-furnace refining equipment in steel production. It is connected to an electric furnace, which can speed up the production cycle of the electric furnace and improve the quality of electric furnace steel. In an embodiment of the present invention, this process does not require the addition of metallic aluminum-containing materials for deoxidation, and adopts low-aluminum silicon calcium barium deoxidation, which is beneficial to the control of Al2O3 brittle inclusions, and ultimately prevents the problem of wire breakage during the welding wire processing process. The alloy composition of the present invention can effectively overcome the problem of brittle fracture caused by the high content of Al elements dissolving into the weld during laser welding. Preferably, the ladle slag composition is controlled to achieve the following goals: in weight ratio, CaO / SiO2=1.1~1.6; in weight percentage, (FeO+MnO)≤1.0%, Al2O3: 3%~6%, MgO: 4%~7%.

[0047] After the LF furnace refining process is completed, the vacuum treatment process of step S103 is entered to carry out rare earth and easily burnable elements alloying, degassing and inclusion removal treatment. Among them, easily burnable elements include Zr and Ti. In this process, it is preferred to control the vacuum degree ≤3mbar, the processing time is 20~25min, and the circulation time after alloying the easily burnable elements is ≥10min, and the argon is soft-blown for 25~35min after breaking the air before leaving the station.

[0048] The billet continuous casting process of step S104 needs to be fully protected during the casting process. The continuous casting parameters are reasonably controlled according to the size of the billet. In the embodiment of the present invention, for a 200mm×200mm billet, the superheat is controlled to be 20-25°C, and the reduction is controlled to be 3-5mm.

[0049] The following is a specific embodiment of the method for preparing steel for welding wire for hot stamping steel with aluminum-based or aluminum-silicon-based coating according to the present invention and its specific process parameters.

[0050] The specific chemical composition of the steel for welding wire prepared in Examples 1-5 is shown in Table 1:

[0051] Table 1 Chemical composition of steel materials for welding wire (wt.%)

[0052]

[0053] Example 1

[0054] This embodiment aims to smelt aluminum-based or aluminum-silicon-based coated hot stamping steel laser welding wire with C>0.06%, and specifically includes the following steps:

[0055] Step S101: Electric furnace smelting process, using clean scrap steel (P: 0.012%, S: 0.008%, other alloy contents do not exceed the upper limit of steel grade design requirements), argon is blown at the bottom during the whole smelting process, and Ni is alloyed in the electric furnace. Among them, the following smelting parameters are controlled:

[0056] End point carbon 0.05%, end point phosphorus 0.008%, end point temperature 1662℃;

[0057] Argon is blown throughout the steel production process, and lime is added at a ratio of 5 kg per ton of steel after 2 / 3 of the steel is produced;

[0058] After 1 / 3 of the steel is tapped, low aluminum silicon calcium barium is used for deoxidation, and the oxygen level after the furnace is set at 15ppm;

[0059] After steel tapping is completed, calcium-based slag modifier is added at a ratio of 4 kg / ton of steel.

[0060] Step S102: LF furnace refining process, desulfurizing the deoxidized molten steel, alloying Nb, Cr, Mo and regulating the composition of the ladle slag, in terms of weight ratio, CaO / SiO2=1.2; in terms of weight percentage, (FeO+MnO) is 0.8%, Al2O3: 3.6%, MgO: 4.3%.

[0061] Step S103: vacuum treatment process, alloying the molten steel with rare earth, Zr and Ti, degassing and removing inclusions, controlling the vacuum to ≤3mbar and processing time for 20min, including a circulation time of 12min after alloying, and soft blowing of argon for 28min after breaking the air before leaving the station.

[0062] Step S104: 200×200 mm small square billets are continuously cast, with full protection pouring, superheat of 21° C., and light pressure reduction of 5 mm.

[0063] The total oxygen content of the steel ingot for laser welding welding wire of aluminum-based or aluminum-silicon-based hot stamping steel smelted in this implementation is ≤10ppm, and the welding wire yield rate is 99.3%.

[0064] Example 2

[0065] This embodiment aims to smelt aluminum-based or aluminum-silicon-based coated hot stamping steel laser welding wire with C>0.06%, and specifically includes the following steps:

[0066] Step S101: Electric furnace smelting process, using clean scrap steel (P: 0.011%, S: 0.005%, and the other alloy contents do not exceed the upper limit of the steel grade design requirements), argon is blown at the bottom during the smelting process, and Ni is alloyed in the electric furnace. Among them, the following smelting parameters are controlled:

[0067] End point carbon 0.04%, end point phosphorus 0.008%, end point temperature 1671℃;

[0068] The steel is produced by blowing argon throughout the process. After 2 / 3 of the steel is produced, lime is added at a ratio of 6 kg per ton of steel.

[0069] After 1 / 3 of the steel is tapped, low aluminum silicon calcium barium is used for deoxidation, and the oxygen level after the furnace is set at 18ppm;

[0070] After steel tapping is completed, calcium-based slag modifier is added at a ratio of 5kg / ton of steel.

[0071] Step S102: LF furnace refining process, desulfurizing the deoxidized molten steel, alloying Nb, Cr, Mo and regulating the composition of the ladle slag, in terms of weight ratio, CaO / SiO2=1.4; in terms of weight percentage, (FeO+MnO) is 0.7%, Al2O3: 4.1%, MgO: 5.2%.

[0072] Step S103: vacuum treatment process, alloying rare earth, Zr and Ti in molten steel, degassing and removing inclusions, controlling vacuum ≤ 3mbar, processing time 23min, including 14min circulation time after alloying, and 31min soft argon blowing after breaking air before leaving the station.

[0073] Step S104: 200×200 mm small square billets are continuously cast, with full protection pouring, superheat of 23° C., and light pressure reduction of 4 mm.

[0074] The total oxygen content of the steel ingot for laser welding wire of aluminum-based or aluminum-silicon-based hot stamping steel smelted in this embodiment is ≤10ppm, and the welding wire yield rate is 98.7%.

[0075] Example 3

[0076] This embodiment aims to smelt aluminum-based or aluminum-silicon-based coated hot stamping steel laser welding wire with C≤0.06%, and specifically includes the following steps:

[0077] Step S101: Electric furnace smelting process, using clean scrap steel (P: 0.011%, S: 0.005%, and the other alloy contents do not exceed the upper limit of the steel grade design requirements), argon is blown at the bottom during the smelting process, and Ni is alloyed in the electric furnace. Among them, the following smelting parameters are controlled:

[0078] End point carbon 0.03%, end point phosphorus 0.007%, end point temperature 1674℃;

[0079] The whole process of steelmaking is argon blowing, and lime is added to the mixed flushing after 2 / 3 of the steel is out, 4kg per ton of steel;

[0080] Steel is not deoxidized during tapping;

[0081] After steel tapping, add 2kg / ton of steel of calcium-based slag modifier;

[0082] After steel tapping is completed, it enters the vacuum decarburization process. The carbon content after decarburization is 0.0018%. After decarburization, no deoxidation is done. Calcium-based steel slag modifier is added to the slag surface at a ratio of 2kg / ton of steel. Then a small amount of argon is blown and stirred for 5 minutes. After the argon blowing is completed, it enters the LF oxygen determination, and the oxygen activity is 321ppm. According to the oxygen determination result, low aluminum silicon calcium barium is added for deoxidation. The oxygen activity after deoxidation is 14ppm.

[0083] Step S102: LF furnace refining process, desulfurizing the deoxidized molten steel, alloying Nb, Cr, Mo and regulating the composition of the ladle slag, in terms of weight ratio, CaO / SiO2=1.5; in terms of weight percentage, (FeO+MnO) is 0.9%, Al2O3: 5.6%, MgO: 6.4%;

[0084] Step S103: vacuum treatment process, alloying rare earth, Zr and Ti in molten steel, degassing and removing inclusions, controlling vacuum ≤ 3mbar and processing time 25min, including 16min of circulation time after alloying, and soft blowing of argon for 35min after breaking air before leaving the station.

[0085] Step S104: 200×200 mm small square billets are continuously cast, with full protection pouring, superheat of 23° C., and light pressure reduction of 3 mm.

[0086] The total oxygen content of the steel ingot for laser tailor-made welding wire of aluminum-based or aluminum-silicon-based hot stamping steel smelted in this implementation is ≤10ppm, and the welding wire yield rate is 99.0%.

[0087] Example 4

[0088] This embodiment aims to smelt aluminum-based or aluminum-silicon-based coated hot stamping steel laser welding wire with C≤0.06%, and specifically includes the following steps:

[0089] Step S101: Electric furnace smelting process, using clean scrap steel (P: 0.011%, S: 0.005%, and the other alloy contents do not exceed the upper limit of the steel grade design requirements), argon is blown at the bottom during the smelting process, and Ni is alloyed in the electric furnace. Among them, the following smelting parameters are controlled:

[0090] End point carbon 0.03%, end point phosphorus 0.007%, end point temperature 1674℃;

[0091] The whole process of steelmaking is argon blowing, and lime is added to the mixed flushing after 2 / 3 of the steel is out, 5kg per ton of steel;

[0092] Steel is not deoxidized during tapping;

[0093] After steel tapping, add 3kg / ton of steel of calcium-based slag modifier;

[0094] After steel tapping is completed, it enters the vacuum decarburization process. The carbon content after decarburization is 0.0018%. After decarburization, no deoxidation is done. Calcium-based steel slag modifier is added to the slag surface at a ratio of 1kg / ton of steel, and then a small amount of argon is blown and stirred for 5 minutes. After the argon blowing is completed, it enters the LF oxygen determination, and the oxygen activity is 350ppm. According to the oxygen determination result, low aluminum silicon calcium barium is added for deoxidation. The oxygen activity after deoxidation is 18ppm.

[0095] Step S102: LF furnace refining process, desulfurizing the deoxidized molten steel, alloying Nb, Cr, Mo and regulating the composition of the ladle slag, in terms of weight ratio, CaO / SiO2=1.1; in terms of weight percentage, (FeO+MnO) is 0.5%, Al2O3: 6%, MgO: 4%;

[0096] Step S103: vacuum treatment process, alloying rare earth, Zr and Ti in molten steel, degassing and removing inclusions, controlling vacuum ≤ 3mbar and processing time 25min, including 16min of circulation time after alloying, and soft blowing of argon for 35min after breaking air before leaving the station.

[0097] Step S104: 200×200 mm small square billets are continuously cast, with full protection pouring, superheat of 20° C., and light pressure reduction of 4 mm.

[0098] The total oxygen content of the steel ingot for laser welding welding wire of aluminum-based or aluminum-silicon-based hot stamping steel smelted in this implementation is ≤10ppm, and the welding wire yield rate is 99.7%.

[0099] Example 5

[0100] This embodiment aims to smelt aluminum-based or aluminum-silicon-based coated hot stamping steel laser welding wire with C>0.06%, and specifically includes the following steps:

[0101] Step S101: Electric furnace smelting process, using clean scrap steel (P: 0.012%, S: 0.008%, other alloy contents do not exceed the upper limit of steel grade design requirements), argon is blown at the bottom during the whole smelting process, and Ni is alloyed in the electric furnace. Among them, the following smelting parameters are controlled:

[0102] End point carbon 0.05%, end point phosphorus 0.008%, end point temperature 1662℃;

[0103] The steel is produced by blowing argon throughout the process. After 2 / 3 of the steel is produced, lime is added at a ratio of 3 kg per ton of steel.

[0104] After 1 / 3 of the steel is tapped, low aluminum silicon calcium barium is used for deoxidation, and the oxygen level after the furnace is set at 15ppm;

[0105] After steel tapping is completed, calcium-based slag modifier is added at a ratio of 6 kg / ton of steel.

[0106] Step S102: LF furnace refining process, desulfurizing the deoxidized molten steel, alloying Nb, Cr, Mo and regulating the composition of the ladle slag, in terms of weight ratio, CaO / SiO2=1.6; in terms of weight percentage, (FeO+MnO) is 0.6%, Al2O3: 3%, MgO: 7%.

[0107] Step S103: vacuum treatment process, alloying the molten steel with rare earth, Zr and Ti, degassing and removing inclusions, controlling the vacuum to ≤3mbar and processing time for 20min, including a circulation time of 12min after alloying, and soft blowing of argon for 28min after breaking the air before leaving the station.

[0108] Step S104: 200×200 mm small square billets are continuously cast, with full protection pouring, superheat of 25° C., and light reduction of 5 mm.

[0109] The total oxygen content of the steel ingot for laser welding welding wire of the aluminum-based or aluminum-silicon-based coated hot stamping steel smelted in this embodiment is ≤10ppm, and the welding wire yield is 98.5%. According to the alloy composition and continuous casting process of the present invention, more than 10 furnaces can be continuously cast. Through the control of refined slag optimization + protective casting, the total oxygen content of the steel ingot for welding wire can be ≤10ppm, and the welding wire yield is as high as more than 98%. Its yield is more than 10% higher than that of conventional Al-containing alloys.

[0110] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for smelting steel for aluminum-based or aluminum-silicon-based coated hot stamping steel laser welding wire, characterized in that: The welding wire steel is composed of the following chemical components in weight percentage: C: 0.01%~0.30%, Si: 0.6%~1.3%, Mn: 1.6%~2.8%, S: 0.008%~0.018%; Cr: 0.4%~3.0%, Mo: 0.5%~2.0%, Ni: 1.6%~4.0%, Zr+Ti+Nb: 0.05%~0.1%, RE: 0~0.02%, P≤0.010%, Al≤0.005%, and the balance is Fe and unavoidable impurities. The smelting method comprises the following steps: Electric furnace smelting process: clean scrap steel is used as the charge for smelting, and Ni alloying is completed in the electric furnace, wherein P≤0.030%, S≤0.020% in the clean scrap steel, and the remaining alloy content meets the chemical composition of steel for welding wire, wherein, When smelting welding wire steel with C>0.06%, low aluminum silicon calcium barium deoxidation is used after 1 / 3 of the steel is tapped, and the oxygen is set to an oxygen activity of ≤20ppm after the furnace. After the steel is tapped, a calcium-based slag modifier is added to the slag surface at a ratio of 3~5kg / ton of steel; When smelting steel for welding wire with C≤0.06%, add calcium-based steel slag modifier to the slag surface at a ratio of 1~3kg / ton of steel after steel tapping, reduce the C content to less than 0.002% through vacuum decarburization process, add calcium-based steel slag modifier to the slag surface at a ratio of 1~3kg / ton of steel after decarburization, blow argon and stir, then enter the LF furnace, use low aluminum silicon calcium barium deoxidation, and set the oxygen to an oxygen activity of ≤20ppm; LF furnace refining process: desulfurization of molten steel, alloying of non-burnable elements, and control of ladle slag composition; Vacuum treatment process: alloying rare earth and easily burnt elements in molten steel, degassing and removing inclusions; Billet continuous casting process: full protection of pouring.

2. The smelting method according to claim 1, characterized in that: Zr+Ti+Nb is any one of Zr+Ti+Nb, Zr+Nb, Zr+Ti, Ti, and Ti+Nb; RE is one or more of La, Ce, and Y elements.

3. The smelting method according to claim 1, characterized in that: In the electric furnace smelting process, the end point carbon is controlled to be ≤0.05%, the end point phosphorus is controlled to be ≤0.008%, and the end point temperature is controlled to be ≥1660°C.

4. The smelting method according to claim 3, characterized in that: In the electric furnace smelting process, argon is blown throughout the steel-making process.

5. The smelting method according to claim 4, characterized in that: In the electric furnace smelting process, After 2 / 3 of the steel is discharged, lime is added into the mixture at a ratio of 4-6 kg / ton of steel.

6. The smelting method according to claim 1, characterized in that: In the LF furnace refining process, the ladle slag composition is controlled to meet the following requirements: In terms of weight ratio, CaO / SiO2=1.1~1.6; In terms of weight percentage, (FeO+MnO) ≤1.0%, Al2O3: 3%~6%, MgO: 4%~7%.

7. The smelting method according to claim 1, characterized in that: In the vacuum treatment process, the vacuum degree is controlled to be ≤3mbar, and the treatment time is 20-25min. The circulation time after alloying of the easily burnt elements is ≥10min, and the station is exited after soft blowing of argon for 25-35min after breaking the air.

8. The smelting method according to claim 1, characterized in that: For 200mm×200mm small square billets, the superheat is controlled at 20~25℃ and the reduction is controlled at 3~5mm.

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