Low-temperature engineering steel with yield strength not lower than 550MPa and production method of engineering steel

Abstract

The invention discloses low-temperature engineering steel with yield strength not lower than 550MPa. The low-temperature engineering steel with yield strength not lower than 550MPa comprises the following components in percentage by weight: 0.04%-0.18% of C, 0.15%-0.50% of Si, 1.63%-2.00% of Mn, not more than 0..015% of P, not more than 0.008% of S, 0.05%-0.12% of Nb+Ti, 0.20%-0.4% of Mo+Cr, and 0.015%-0.05% of Als; the production steps are as follows: smelting and continuously casting to form blank, heating up the casting blank; rolling in a segmented manner by adopting a TMCP (Thermo-Mechanical Control Process); cooling; and straightening for the future use. The low-temperature engineering steel with yield strength not lower than 550MPa disclosed by the invention is not only capable of producing a steel plate with the thickness bigger than 80mm; the steel plate is uniform in tissue performance in the thickness direction, better in low-temperature impact toughness, i.e., impact power being not less than 100J at (-)60 DEG C, suitable for manufacturing engineering machinery that works in an extremely cold environment. The casting blank has center segregation C lower than 1.5 level and center porosity lower than 0.5 level; the low-temperature engineering steel is free of Ni and relatively low in content of Cr, Mo and other micro alloys, so that the cost is greatly lowered; the TMCP is adopted for producing without the processes including thermal treatment, PRC (Pre-stressed Reinforced Concrete), stacking slow-cooling and the like, and any other equipment is not needed to be added, so that the production process is simple and the production efficiency is high.

Description

Technical field [0001] The invention relates to steel for engineering machinery and a production method thereof, in particular to low-temperature engineering steel with a yield strength ≥550MPa and a production method thereof. Background technique [0002] High-strength engineering machinery steel is mainly used to manufacture engineering machinery structural parts. Due to the limitation of service conditions and welding process, steel plates for this type of use not only require the material to have sufficient strength, plasticity and welding performance, but also require excellent low-temperature impact Toughness to adapt to field operations in extreme harsh environments. With the development of large-scale and light-weight construction machinery, the market demand for extra-thick steel plates for high-strength construction machinery is on the rise. [0003] Traditional high-strength, high-toughness and extra-thick steel plates are mainly produced by quenching and tempering proc...

AI Technical Summary

Problems solved by technology

[0003] The traditional high-strength and high-toughness extra-thick steel plate is mainly produced by quenching and tempering process to obtain martensitic tempered structure with excellent strength and toughness. Cracks and surface defects appear, reducing the yield

Its advantage is that the addition of alloy elements is low and the proportion is free, and the thickness reaches more than 120mm. Its disadvantages are: the use of die casting casting reduces the production efficiency compared with the continuous casting process; the use of normalizing heat treatment process increases the production cycle ; In terms of performance, the strength and low-temperature impact toughness are not enough to meet the long-term use of large-scale construction machinery in low-temperature environments, and the service life and construction capacity of the whole machine will not be greatly improved

However, the strength and low-temperature impact toughness are too low, so it is not suitable for manufacturing large-scale construction machinery used in low-temperature environments

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