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CN-122012861-A - Full-flow control method for steel stamping sand hole defects for new energy battery case

CN122012861ACN 122012861 ACN122012861 ACN 122012861ACN-122012861-A

Abstract

The invention discloses a full-flow control method for steel stamping sand hole defects for a new energy battery case, and belongs to the technical field of ferrous metallurgy. The method takes the cooperative control of the whole-flow low temperature and the low oxygen potential as the core, and comprises the steps of desulfurizing and dephosphorizing molten iron pretreatment, low superheat smelting of a converter, tapping temperature 1580-1620 ℃, ladle top slag modification in the tapping process, control of top slag (FeO+MnO) to be less than or equal to 5%, RH vacuum deep refining combined with step calcium treatment, weak stirring and precise temperature adjustment in LF, and continuous casting adopting a six-hole argon blowing composite technology of brick sitting and annular argon blowing on a submerged nozzle and a stopper rod, and an optimized rolling and annealing process. According to the invention, through systematic process route design, large-size inclusions are controlled cooperatively from multiple dimensions of source inhibition, process removal and end anti-blocking, the content of inclusions which are more than or equal to 5 mu m in the battery case steel is reduced to less than or equal to 1/mm < 2 >, the defect rate of punching sand holes is controlled below 0.1%, the purity and the forming reliability of the battery case steel are obviously improved, and the method is suitable for the production of high-end new energy battery cases.

Inventors

  • DI YANJUN
  • ZHAO XIAOLONG
  • QU TIANPENG
  • QIN JUNSHAN
  • LIN XIAOLIANG
  • GUO YUANQIANG
  • ZHANG KAI
  • WANG DEYONG

Assignees

  • 甘肃酒钢集团宏兴钢铁股份有限公司

Dates

Publication Date
20260512
Application Date
20260305

Claims (10)

  1. 1. The full-flow control method for the steel stamping sand hole defect for the new energy battery shell is characterized by adopting a process route of molten iron pretreatment, converter smelting, ladle top slag modification, RH vacuum refining, LF temperature regulation, continuous casting and rolling, and comprising the following steps of: S1, preprocessing molten iron, namely sequentially carrying out desulfurization and dephosphorization preprocessing on the molten iron, and controlling the sulfur content of the molten iron to be less than or equal to 0.005% and the phosphorus content to be less than or equal to 0.008%; s2, converter smelting, namely carrying out converter smelting on the pretreated molten iron, controlling the tapping temperature at the end point to be 1580-1620 ℃, carrying out deoxidization alloying in the tapping process, and controlling the oxygen content of the molten steel to be less than or equal to 20ppm; S3, ladle top slag modification, namely adding a modifier into a ladle in the tapping process of the converter, and controlling the FeO+MnO content in the top slag to be less than or equal to 5% by matching with bottom argon blowing stirring; S4, RH vacuum refining, namely carrying out RH vacuum treatment on molten steel, wherein the vacuum degree is less than or equal to 50Pa, the treatment time is 22-28 min, ca-Si wires are fed step by step, and a soft blowing process is adopted, so that the T [ O ] of the treated molten steel is less than or equal to 12ppm; S5, LF temperature regulation, namely LF refining is carried out on the molten steel subjected to RH treatment, and only temperature regulation is carried out, so that the temperature of the molten steel is accurately regulated and controlled to 1540-1560 ℃; S6, continuous casting, namely casting by adopting a submerged nozzle, annular argon blowing is carried out at a brick-sitting position on the submerged nozzle, and meanwhile, a porous argon blowing is arranged at the head of a stopper rod, the flow of argon is controlled in a compound manner, and the protection and the sectional cooling of a crystallizer are matched; And S7, rolling, namely heating, rough rolling, finish rolling, cold rolling and continuous annealing treatment are carried out on the continuous casting billet.
  2. 2. The method according to claim 1, wherein in the step S2, the final carbon content is controlled to be 0.06-0.09%, si-Mn alloy and Al are used for combined deoxidation, the addition amount of the Si-Mn alloy is 8-10 kg/t steel, and the addition amount of the Al is 0.2-0.3 kg/t steel.
  3. 3. The method of claim 1, wherein in the step S3, the modifier is CaO-Al 2 O 3 -MgO-CaF 2 composite modifier, the mass percentage of which is 55-65% CaO, 5-8% Al 2 O 3 15~20%,MgO 8~12%,CaF 2 and 2-5% metallic Al, the adding amount is 7-10 kg/t steel, the adding is started when the tapping amount reaches 1/3, the adding is divided into 2-3 batches, and the adding is completed before the tapping amount reaches 2/3.
  4. 4. The method according to claim 1, wherein in the step S3, the argon flow is 0.15-0.20 m 3/(t.min) during tapping, and the argon flow is adjusted to 0.10-0.12 m 3/(t.min) after tapping, and stirring is continued for 8-12 min.
  5. 5. The method according to claim 1, wherein in the step S4, the total Ca-Si wire feeding amount is 0.5-0.7 kg/t steel, and the steel is fed in two steps, wherein 60% of the total Ca-Si wire feeding amount is fed in the first step, and after stirring for 5min, the remaining 40% is fed, and the soft argon blowing strength is 0.08-0.12 m 3/(t.min).
  6. 6. The method of claim 1, wherein in the step S5, LF refining adopts low-power heating, the heating power is 300-400 kW, the heating rate is less than or equal to 3 ℃ per minute, weak argon stirring is adopted, the stirring intensity is 0.03-0.05 m < 3 >/(t.min), the stirring time is 5-8 min, and the fluctuation of the temperature of molten steel is controlled to be less than or equal to +/-3 ℃.
  7. 7. The method of claim 1, wherein in the step S6, argon flow rate of annular argon blowing of the brick sitting on the submerged nozzle is 5-8L/min, and 6 argon blowing holes are uniformly formed in the head of the stopper along the circumference, wherein the argon flow rate is 2-3L/min.
  8. 8. The method according to claim 1, wherein in the step S6, the continuous casting drawing speed is 1.2-1.6 m/min, the alkalinity of mold casting powder is 1.2-1.5, the melting temperature is less than or equal to 1300 ℃, the viscosity is 0.8-1.2 Pa.s, the sectional cooling strength of the secondary cooling zone is that one section of steel is 0.8-1.0L/kg, two sections of steel are 0.5-0.7L/kg, and the casting blank straightening section temperature is 900-950 ℃.
  9. 9. The method of claim 1, wherein in the step S7, the heating process is that the preheating section temperature is 800-900 ℃, the heating section is 1150-1200 ℃, the soaking section is 1180-1220 ℃, the total heating time is 2.5-3.5 h, the rough rolling pass reduction is 15-25%, the accumulated reduction is more than or equal to 70%, the finish rolling pass reduction is 5-10%, the finish rolling temperature is 850-900 ℃, the cold rolling total reduction is 70-80%, the continuous annealing temperature is 750-800 ℃, the heat preservation time is 30-40S, and the cooling speed is 15-20 ℃ per second.
  10. 10. The method according to any one of claims 1 to 9, wherein the final product has a large-size inclusion content of not less than 5 μm of not more than 1/mm 2, a punch void defect rate of not more than 0.1%, a yield strength of not less than 300MPa, and an elongation of not less than 35%.

Description

Full-flow control method for steel stamping sand hole defects for new energy battery case Technical Field The invention belongs to the technical field of ferrous metallurgy, relates to a production method of a cold-rolled steel sheet for a new energy battery shell, and in particular relates to a method for carrying out full-flow cooperative control on sand hole defects in a stamping forming process, and realizes accurate control of large-size inclusions through full-flow cooperative control of molten iron pretreatment, converter smelting, RH vacuum refining, LF temperature regulation, continuous casting and steel rolling. Background With the rapid development of the new energy automobile industry, extremely high requirements are put on the safety, reliability and service life of the power battery. The battery shell is used as a core structural member of the power battery and is generally manufactured by adopting ultra-deep drawing cold-rolled steel plates through multi-pass stamping. In the stamping process, if nonmetallic inclusions (such as Al 2O3、SiO2、CaO-Al2O3-SiO2 composite inclusions) with large size (usually more than or equal to 5 μm) exist in the steel plate, stress concentration points are formed at deformed parts due to the plasticity difference between the nonmetallic inclusions and the steel matrix, microcracks are induced, and finally 'sand hole' defects are formed on the surface or in the battery shell. Such defects seriously impair the air tightness and structural strength of the battery case, and are one of the key risk sources for causing leakage, short circuit and even thermal runaway of the battery pack. At present, the technology for controlling the steel inclusion of the battery shell has three core problems that a process route lacks a full-flow temperature cooperative control idea, the tapping temperature of a converter is too high to cause the oxidation of molten steel to be increased, the inclusion generation amount is increased from the root, the inclusion control is excessively dependent on LF refining, the deep purification advantage of RH vacuum treatment is not fully exerted, the single-link control is difficult to cope with the evolution of the full-flow inclusion, the oxidizing control of ladle top slag in the tapping process of the converter is ignored, the content of FeO+MnO in the top slag exceeds the standard, oxygen is continuously supplied to the molten steel through slag-metal interface mass transfer after tapping, and Al 2O3 inclusion is secondarily generated. RH treatment is commonly adopted in the prior art, but effective synergy with low tapping temperature of a converter, top slag modification and LF accurate temperature control is not formed, and flocculation problems are easy to occur in the continuous casting process, so that large-size foreign inclusions are further introduced. The unreasonable process layout leads to high defect rate of the battery case steel stamping sand holes, and cannot meet the quality requirement of the high-end battery case. Therefore, the development of a method capable of inhibiting the generation of inclusions from the source and cooperatively controlling the quantity, the size and the shape of the inclusions in the whole process is a key for solving the problem of the sand hole defect of the new energy battery shell steel stamping and improving the product quality. The invention provides a full-process method which takes full-process temperature control as a core, integrates a ladle top slag modification link, optimizes a process route of molten iron pretreatment, converter smelting, ladle top slag modification, RH vacuum refining, LF temperature regulation and control, continuous casting and rolling, highlights RH inclusion control innovation, weakens LF functions, solves the problem of continuous casting nozzle nodulation, fundamentally inhibits inclusion generation, strengthens RH deep purification capability and meets continuous casting requirements through LF accurate temperature control so as to solve the key technical problems in the current battery case steel production field. Disclosure of Invention The invention aims to solve the problems of unreasonable process route, lack of temperature control, dependence on a single link for inclusion control and neglecting the oxidizing property of top slag in the prior art, and provides a full-flow method for controlling the defect of the battery case steel punching sand holes. The method takes the control of the whole process low temperature and low oxygen potential as a core idea, and the physical and chemical conditions of each link are cooperatively controlled by optimizing the whole process route from molten iron to steel rolling, so as to radically inhibit the generation of inclusions, promote the removal of the inclusions and prevent the reintroduction of the inclusions, and finally realize that the content of large-size inclusions which are more than or equal to 5 mu m in t