Ferritic stainless steel and method for manufacturing same

Abstract

The invention relates to a ferritic stainless steel which comprises the following chemical components in percent by weight: 0.001-0.025% of C, less than1.0% of Si, less than 1.0% of Mn, less than 0.03% of P, less than 0.010% of S, 17-20% of Cr, 1.70-2.00% of Mo, less than 0.02% of Al, 0.005-0.025% of N, less than 0.0100% of O, less than 0.2% of Nb, 0.10-0.15% of V, less than 0.5% of Ni and the balance of Fe and inevitable impurities. A method for manufacturing the ferritic stainless steel comprises the following steps: smelting by using a vacuum induction furnace, or by using an electric arc furnace through external refining or by using a converter through external refining; continuously casting, wherein the degree of superheat is controlled at 30-50 DEG C, and the slab pulling speed is controlled at 0.8-2m / min; pouring at 1,580-1,600 DEG C; heating the continuously-cast billet to 1,050-1,100 DEG C, and hot rolling, wherein the finish rolling temperature is 800-900 DEG C, and the hot rolling reduction is more that 90%; cooling in air; continuously annealing the hot-rolled strip steel, and pickling, wherein the annealing temperature is 950-1,050 DEG C, the temperature is preserved for 1-1.5t min, and the t represents the thickness (mm) of the strip steel. The ferritic stainless steel has excellent impact toughness, corrosion resistance and mechanical properties.

Description

technical field [0001] The invention relates to a method capable of improving the impact toughness of ferritic stainless steel and its manufacturing technology, and simultaneously has excellent corrosion resistance and mechanical properties. Background technique [0002] Ultra-pure ferritic stainless steel 444 (18Cr-2Mo) stainless steel has excellent corrosion resistance, crevice corrosion, stress corrosion resistance, intergranular corrosion resistance and high temperature oxidation resistance, and its corrosion resistance is even better than that in some fields. 304 and 316 are currently widely used in heat exchange equipment resistant to weak medium pitting corrosion and fermentation equipment resistant to weak acids such as acetic acid, such as hot water tanks, solar water heaters, water tanks, fermentation and storage tanks, etc. 444 has replaced part of the market volume of 304 in the stainless steel water tank industry. About 90% of 444 has replaced 304 austenitic st...

AI Technical Summary

Problems solved by technology

However, 444 ferritic stainless steel still has some disadvantages, such as poor impact toughness at room temperature and low temperature, resulting in high requirements for cold and hot processing and high temperature requirements for processing and use environments.

Especially when the thickness of the material is greater than 3mm, the brittleness tendency of stainless steel increases significantly, so the application range of this steel is still relatively small

[0003] The impact toughness of 444 ferritic stainless steel is generally low

[0007] CN101168822A discloses a high-toughness nickel-free ferritic stainless steel and its manufacturing method, the patent contains 0.02-0.1 mass fraction of rare earth, the manufacturing process is difficult, and it is not easy to realize at the production site

[0013] CN101285152A discloses a magnetic stainless steel wire rod or steel wire with excellent corrosion resistance, cold workability and toughness. The content of noble metal Nb in this patent is relatively high (0.2-0.8%), and the cost is relatively high

[0014] CN1104686A discloses a ferritic stainless steel with good atmospheric corrosion resistance and crevice corrosion resistance. This patent contains high P, with a mass fraction of 0.04% to 0.2%. Performance, the patent is difficult to produce, the application field is relatively special, and the scope is narrow

[0015] EP1408132B1 discloses a stainless steel plate with excellent deep drawing properties, tensile properties, high-temperature strength, high-temperature oxidation resistance and low-temperature toughness. The chemical composition of this invention contains B and rare earth elements, and the metallurgy is difficult

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