Continuous annealing production method of cold-rolled sheet No.45 steel

Abstract

The invention relates to a continuous annealing production method of cold-rolled sheet No.45 steel. The steel comprises the following components in percentage by weight: 0.47 percent of C, 0.60 percent of Mn, 0.31 percent of Si, less than or equal to 0.035 percent of P, less than or equal to 0.035 percent of S, less than or equal to 0.025 percent of Cr, less than or equal to 0.025 percent of Ni, less than or equal to 0.025 percent of Cu and the balance of Fe. In the method, the heating temperature of a hot rolling process is controlled to be 1,250+ / -30 DEG C, the final rolling temperature is 900+ / -20 DEG C, the reeling temperature is 730+ / -20 DEG C; and the cold rolling down rate of a cold rolling process is controlled to be 50-70 percent. The continuous annealing process comprises the following steps of: putting band steel into a nonoxidative atmosphere consisting of H2 and N2 as a medium in a furnace from room temperature and heating up to 240-260 DEG C through 37-52 seconds; further heating up to 750-770 DEG C through 670-850 seconds; preserving heat for 214-300 seconds; cooling to 590-610 DEG C through 60-85 seconds; cooling to 440-460 DEG C through 13-19 seconds; and cooling to 390-410 DEG C through 789-1,105 seconds, and then cooling to room temperature with water. A continuous annealing steel plate produced by the invention has higher strength and elongation, thus the product quality is improved.

Description

Technical field [0001] The invention relates to a continuous annealing production method for cold-rolled sheet 45 steel, which belongs to the field of metal material processing. Background technique [0002] The 45# steel finished product can be used in the automotive industry and construction fields. The mass fraction of carbon in No. 45 steel is relatively low, and there are fewer undissolved carbonized material spots in austenite during annealing, and spheroidization is more difficult. From the energy point of view, spherical cementite has the smallest interface area per unit volume and is the most stable structure in steel, so it has the lowest interface energy. Due to the above reasons, ordinary continuous annealing is easy to produce a network of cementite structure to separate the ferrite, so the low plasticity leads to stamping deformation and cracking. Attached figure 1 It is a photo of the microstructure of No. 45 steel after cold rolling. The crystal grains are obvio...

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Problems solved by technology

[0003] The object of the present invention is to provide a continuous annealing production method of No. 45 cold-rolled thin plate steel to solve the problem of pearlite dispersion and spheroidization in the continuous annealing production process of No. 45 steel question

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