Production method of ultra-low carbon interstitial-free mild steel

Abstract

The invention discloses a production method of ultralow-carbon interstitial free soft steel, which comprises the following steps: hot rolling, cold rolling and cover annealing. The casting blank adopted by the hot rolling comprises the following components in percentage by weight: at most 50 ppm of C, at most 0.15% of Mn, at most 0.010% of S, at most 0.020% of P, greater than or equal to 0.10% and less than or equal to 0.20% of Si, at most 0.070% of Ti, 200-500 ppm of Als, at most 25 ppm of Ca, at most 50 ppm of N and the balance of Fe. In the hot rolling, a forepart cooling process is adopted, the finishing temperature is 900+ / -20 DEG C, and the coiling temperature is 700+ / -20 DEG C. In the cold rolling, the reduction in cold rolling is greater than or equal to 70%. In the cover annealing, an all-hydrogen cover annealing furnace is adopted, the dew point is lower than -50 DEG C, the hot-spot temperature is 740+ / -10 DEG C, the cold-point temperature is 720+ / -10 DEG C, and the holding time is 20-25 hours. By improving the steel grade components, improving the production process by Si alloying and enhancing the processability of the finished product, the method has the advantages of simple technique and no additional increase of cost; the experimental production is performed to obtain the expected effect; and the production process is stable, and the finished product has excellent performance.

Description

technical field [0001] The invention relates to a production method of steel, in particular to a production method of ultra-low carbon interstitial atom-free soft steel. Background technique [0002] In order to meet the weight reduction requirements of steel for auto parts, high-strength steels, especially advanced high-strength steels, are increasingly used in car bodies, but soft steels, such as deep-drawing and ultra-deep-drawing steels, have excellent formability in Automobile panels still play an irreplaceable role in the manufacture of automotive panels, such as the production of engine covers, fenders and other parts, so the proportion of application in the body is relatively fixed, and there are high requirements for the forming properties of materials, such as In the process of use, these steel types are required to have good anti-thinning properties in the stamping or forming process, that is, high plastic strain ratio, and in different orientations (especially 0 ...

AI Technical Summary

Problems solved by technology

For example, the patent of Publication No. CN101880827A provides an IF steel with △r≤0.3 and its production method. In order to obtain IF steel with small difference in isotropic properties, the interstitial-free steel with Δr≤0.3 is obtained by compound alloying with Nb and Ti , but Nb alloying will increase the cost and the plasticity is weaker than Ti alloyed IF steel

[0003] For IF steel (ultra-low carbon interstitial-free soft steel), there are currently two main production routes: 1) Converter steelmaking→RH vacuum degassing treatment→hot rolling→cold rolling→annealing→tempering, etc., during the RH treatment process Among them, including the use of Al final deoxidation, Ti alloying (if it contains Nb, it will be added during the converter tapping process), and occasionally the temperature of aluminum and oxygen is raised to make up for the lack of temperature (not necessary), this method is the most commonly used; because The use of Al deoxidation will increase the difficulty of continuous casting; 2) Other processes are the same as 1, and the refining process adopts double-linking, that is, RH→LF or LF→RH, such as a thin slab continuous casting and rolling production IF disclosed in the publication number CN1974824A The production process of steel, which uses electrode heating in the LF furnace, is difficult to control carbon, resulting in large fluctuations in performance and increased costs

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