High-strength and high-toughness hot-rolled round steel capable of being directly cut and preparation method thereof

Abstract

The invention relates to high-strength and high-toughness hot-rolled round steel capable of being directly cut and a preparation method thereof. Elements of the round steel contain Nb, V and other microalloys, so that grain refinement and strength improvement are facilitated. Two-stage rolling of cogging and continuous rolling is adopted, air cooling temperature holding is carried out before two times of rolling, a steel billet is overturned by 180 degrees through a cogging mill during first-time air cooling temperature holding, and after first-time temperature holding, the steel billet is roughly rolled into an intermediate square billet through the cogging mill; second-time air cooling temperature holding is performed before continuous rolling of the intermediate square billet, the temperature of the intermediate billet is held to the initial temperature of continuous rolling of 800-950 DEG C, the intermediate billet is continuously rolled into the round steel by using a continuous rolling machine after the second-time temperature holding, and the final rolling temperature is 780-900 DEG C; and when the temperature of the round steel subjected to hot rolling is held to be lower than Ar3, the round steel is comprehensively cooled through spraying and air cooling, after being cooled to 600 DEG C, the round steel is subjected to stack cooling to obtain a microstructure of lamellar pearlite and a small amount of ferrite.

Description

technical field [0001] The invention belongs to the technical field of iron-based alloys, and in particular relates to a hot-rolled round steel that can be directly cut without quenching and tempering treatment. Background technique [0002] Hot-rolled round steel for direct cutting is widely used to replace 45, 40Cr, 42CrMo and other quenched and tempered steels to produce injection molding machine tie rods, engineering vehicle cylinder piston rods and other various rod parts. Compared with traditional quenched and tempered steel, because the heat treatment after rolling is omitted in the process, the production cycle is shorter and the production cost is lower, so as to achieve the production goals of energy saving, cost reduction, emission reduction and efficiency increase. However, this type of hot-rolled round steel generally needs to be warmed during rolling to achieve low-temperature rolling; in addition, in order to ensure higher strength and toughness, a higher cont...

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Problems solved by technology

[0007] Patent application CN 201711100874 discloses a non-quenched and tempered steel and its preparation method, the non-quenched and tempered steel of the invention, by weight percentage, C: 0.46-0.55%, Si: 0.20-0.60%, Mn: 1.20-1.60% , Cr: 0.00-0.30%, Al: 0.010-0.030%, Ni: 0.10-0.30%, Cu: 0.00-0.20%, P: 0.000-0.030%, S: 0.020-0.050%, V: 0.050-0.250%, Nb: 0.020-0.050%, Ti: 0.010-0.030%, B: 0.0005-0.0030, N: 0.012-0.020%, the balance is Fe, the patent application product contains higher alloys Mn, V, Nb, Ti, B , the cost of materials is high, and it needs to be finished at 780-850°C for final rolling, and the production efficiency is low

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