Rolling process of Ti-containing low alloy steel

Abstract

The invention relates to a rolling process of Ti-containing low alloy steel. The steel comprises the following components in percent by mass: 0.13-0.15% of C, 0.20-0.40% of Si, 0.70-0.90% of Mn, lessthan or equal to 0.020% of P, less than or equal to 0.020% of S, 0.003-0.020% of Al, 0.045-0.065% of Ti, less than or equal to 0.30% of CEV and the balance Fe and inevitable impurity elements. The rolling process comprises the following steps of S1, producing a proper slab in a steelmaking step; S2, directly heating the slab in the step 1 at a high temperature; S3, roughly rolling the slab heatedat the high temperature in the step 2; S4, carrying out finish rolling on the roughly rolled slab in the step 3; S5, carrying out ultra fast cooling on the slab after finish rolling in the step 4; andS6, cooling the slab to 800-820 DEG C in the step 5 and carrying out air cooling on the slab. The rolling process overcomes the defects in the prior art and meets the demand of steel rolling production of a low cost low alloy steel plate.

Description

technical field [0001] The invention relates to a rolling process of Ti-containing low-alloy steel, which belongs to the technical field of steelmaking. Background technique [0002] Q355 and Q235 series steels are currently the most used in actual use, especially the low-alloy steel Q355 series (Q345 series in the original GB / T1591-2008) steel mills use Ti and Nb microalloying supplemented by suitable rolling in production. The manufacturing process produces qualified products, which greatly reduces the production cost. [0003] The main process of rolling Ti-containing steel is heating-rough rolling-finish rolling-controlled cooling and other basic processes. [0004] Ti exists in two forms in steel: TiN and TiC. TiN is formed in the solidification stage of molten steel and is actually insoluble in austenite. TiN does not decompose and precipitate during the heating and cooling process of steel, so it can control the crystallization in the heating process of steel and in...

AI Technical Summary

Problems solved by technology

[0010] The main defects of the Ti-containing low-alloy medium and thick plate produced by the TMCP process in the prior art are: the finishing rolling temperature of the thin steel plate is low, resulting in low yield strength of the steel plate; Production of waste products; temperature control of the intermediate billet, low hourly output of the rolling mill; high ACC cooling rate and low reddening temperature, the steel plate produces granular bainite structure, resulting in a large number of unqualified elongation of the steel plate, and a large number of cracks in the cold bending of the steel plate; the steel plate is straightened by ACC Finally, the bainite phase transformation on the surface of the steel plate deforms and drifts when the cooling bed is in progress; the high dislocation density of the steel plate and the large thermal stress cause large internal stress, warpage occurs after cutting, and the steel plate bends and brittle fractures; Poor shape, warpage after cutting, bending cracking and brittle fracture, and tube coil cracking cause a lot of quality objections; after the steel plate is produced by TMCP process, uneven cooling causes unstable performance, especially unstable impact value

Therefore, due to the above defects, the production steel plants basically do not produce low-cost Ti-containing low-alloy medium and heavy plates.

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