Production method of high-strength steel plate for engineering machinery

Abstract

The invention discloses a production method of a high-strength steel plate for engineering machinery. The steel comprises the following components of, in percentage by weight, 0.10%-0.25% of C, less than or equal to 0.80% of Si, 0.80%-1.20% of Mn, less than or equal to 0.010% of P, less than or equal to 0.0015% of S, 0.005%-0.015% of Al, less than or equal to 1.0% of Cr, less than or equal to 1.0% of Mo, 0.30%-2.0% of Ni, less than or equal to 0.30% of Cu, less than or equal to 0.015% of Ti, less than or equal to 0.020% of Nb, less than or equal to 0.080% of V, less than or equal to 0.0040% of B, less than or equal to 0.0040% of N, less than or equal to 0.0010% of O, less than or equal to 0.00015% of H, more than or equal to 95% of Fe and inevitable impurities; the process of the steel plate comprises the steps of smelting, refining, continuous casting, rolling and heat treatment; and the structure of the steel plate comprises a lath martensite matrix and a small amount of retained austenite, 5%-10% of the retained austenite is arranged on the upper surface of the steel plate, and 2%-5% of the retained austenite is arranged on the lower surface of the steel plate. The steel plate has good comprehensive mechanical properties, pure steel quality, uniform performance in transverse and longitudinal structures and rolling direction, good plate shape and surface quality and low residual stress, and shows excellent whole plate bending capacity in the rolling direction. The steel plate can be used for manufacturing large engineering machinery such as cranes and pump trucks.

Description

technical field [0001] The invention belongs to the technical field of metallurgy and relates to a production method of high-strength low-alloy steel wide and thick steel plates for engineering machinery. Background technique [0002] Construction machinery refers to the general term for the mechanical equipment required for the construction of national defense, transportation, construction, water conservancy, mining, energy industry and other projects. Since the main components of construction machinery often bear complex and variable heavy loads, the quality requirements for their materials are extremely strict. Low-alloy high-strength steel has good strength and toughness, weldability, crack resistance, fatigue resistance and formability, and is widely used in the field of construction machinery steel. [0003] With the advancement of modern equipment manufacturing technology and the increasing requirements of large-scale engineering projects to improve construction effi...

AI Technical Summary

Problems solved by technology

Therefore, especially for Q1100 steel and Q1300 steel with higher strength levels, it is difficult to achieve such a high elongation requirement by traditional tempering process

Chinese patent CN102226248B adopts the Q+P process, which can obtain more than 10% retained austenite in the martensite matrix, but the strength of the steel is low. When the elongation is 15%, the yield strength only reaches 870MPa

Chinese patent CN102925802B also adopts the Q+P process, which adds higher Mn and more microalloying elements Nb, V, and Ti to compensate for the strength loss caused by the reduction of martensite, but Mn and Nb are prone to central segregation , is especially harmful to high-strength steel, and adding excessive Ti (0.035%~0.045%) will form undeformable large-sized TiN and TiC particles with sharp edges and corners, which is not only unfavorable to uniform elongation, but also seriously affects the fatigue properties of high-strength steel

Chinese patent CN107557548B adopts Q+P+T process in the laboratory to obtain Cr-Ni-Mo low-alloy ultra-high-strength steel with yield strength ≥ 1200MPa and elongation ≥ 15%, but it adds 0.20%~0.40% carbon and relatively Too much Cr, Ni, Mo and other alloying elements will obviously deteriorate the weldability of steel

Chinese patent CN104046908B adopts DQST process (that is, DQ+P process), which can obtain ultra-high strength, good low-temperature ductility, delayed crack resistance and weldability with less alloying elements, but compared with offline quenching, online quenching steel plate It is more difficult to control the shape, and there is inevitably a certain difference in the quenching temperature of the head, middle and tail of the steel plate, resulting in poor performance uniformity in the rolling direction, especially for wide and thick plates with a thickness below 16mm, there are still certain limitations in practical application

Chinese patent CN106191673B, in order to preserve the retained austenite, adopts Q+ strong straightening process to produce a quenched ultra-high strength steel plate, and uses strong cold straightening instead of low temperature tempering to remove quenching residual stress, but strong cold Straightening equipment, and the plate thickness is limited to 4~20mm due to the straightening ability

[0007] Therefore, the main problem of the prior art is: for quenched martensitic steel, if the traditional tempering process is adopted, the plasticity is low, and if the thermal stabilization or mechanical stabilization of austenite is used to improve the plasticity, the strength is reduced; or At the cost of sacrificing welding performance, fatigue performance, plate shape accuracy, surface quality, performance uniformity, etc.; or it will cause problems such as high residual stress, especially micro stress

In addition, most of the existing technologies focus on improving the plasticity of the steel plate to improve the bending performance of the steel plate. The bending ability also has an impact that cannot be ignored; and when the steel plate is bent, how to match the impact of strong plasticity on improving the springback of the steel plate has never been involved

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