Low-cost thick-gauge low-alloy structural steel and production method thereof

Abstract

The invention discloses low alloy structural steel with low cost and thick specification. The low alloy structural steel comprises the following components by weight percent: 0.17%-0.20% of C, 0.15%-0.30% of Si, 0.35%-0.55% of Mn, less than or equal to 0.025% of P, less than or equal to 0.01% of S, less than or equal to 0.008% of N, and the rest of Fe and inevitable impurities. A production method of the structural steel comprises the following steps: (1) continuous casting to obtain billet; (2) soaking the cast billet; (3) high-pressure descaling, and finish rolling, wherein the sum of reduction rates of F1 and F2 is greater than or equal to 98% and is less than or equal to 105%, and F1 and F2 cooling water amount is 70%-80% of normal water amount, F3 or F4 is nominal, and the outlet temperature is 840-870 DEG C; (4) setting the laminar flow cooling speed to be 40-83 DEG C / s, the coiling temperature to be 540-570 DEG C, and the head coiling temperature to be 580-600 DEG C; (5) cooling. The production method disclosed by the invention basically eliminates phenomena such as mixed crystal and cold bending cracking, has good coiling shape, and is suitable for being widely applied to the field of steel production.

Description

technical field [0001] The invention relates to the technical field of iron and steel production, in particular to a low-cost thick-gauge low-alloy structural steel and a production method thereof. Background technique [0002] At present, the thin slab continuous casting and rolling production of domestic large-scale iron and steel enterprises mostly adopts the CSP (Compact Strip Production, compact strip production line) production line, which generally includes two 150-ton converters, two LF (Ladle Refining Furnace, ladle refining furnace) refining furnaces, One RH refining furnace, two-strand thin slab continuous casting line, tunnel heating furnace and seven-stand hot continuous rolling mill. The maximum slab width produced by the casting machine is 1680mm, and the thickness is 70mm and 90mm. The casting machine has the function of casting and rolling with a liquid core. The designed working speed of the machine can reach 5-6m / min. The latest domestic CSP production l...

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Problems solved by technology

[0006] 2) The problem of mixed crystal phenomenon and cold bending cracking, due to the use of low temperature furnace and low temperature rolling, F3 (FinishMill, English free translation of finish rolling, where F3 refers to the third hot rolling mill, F4 refers to the fourth hot rolling mill) or The lower temperature and reduction rate of the F4 pass lead to the occurrence of mixed crystal phenomenon in the finished strip steel, which affects the control of the structure and ultimately affects the customer's cold-formation performance

[0007] 3) The coil shape problem mainly refers to the problem of the overflow edge of the head tower and the head. There are two reasons: ① Due to the low-temperature final rolling and low-temperature coiling, the cooling rate is large and uneven, and the shape of the head is poorly controlled, so it is easy to The head tower shape is generated; ②The shape of the strip head is irregular and the temperature is low at the same time, which affects the detection of the strip head tracking signal, affects the action of the head side guide plate and the action of the pinch roller, resulting in a head tower shape and the head overflow edge; such problems can easily lead to damage and cutting of steel coils during hoisting, serious scrapping of the entire coil, affecting the yield of products, not only increasing labor costs, but also affecting logistics delivery and contract fulfillment, which is not conducive to products Increased competitiveness, see figure 2 Roll-shaped schematic diagram of the Q345B comparative example

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