Steel with good property and ultra-high strength for engineering machinery and manufacturing method thereof

Abstract

The invention discloses steel with good property and ultra-high strength for engineering machinery and a manufacturing method thereof. The steel comprises the following components by weight percent: 0.15 to 0.20 percent of C, 0.35 to 0.55 percent of Si, 0.95 to 1.35 percent of Mn, at most 0.013 percent of P, at most 0.0030 percent of S, 0.75 to 1.25 percent of Cr, 0.45 to 0.65 percent of Mo, 0.0010 to 0.0020 percent of B, 0.005 to 0.013 percent of Ti, 0.010 to 0.030 percent of Nb, 0.030 to 0.070 percent of Al, at most 0.0060 percent of N, at most 0.0030 percent of O, 0.001 to 0.004 percent of Ca, and Fe and inevitable impurities in balance. The invention optimizes the DQ and offline tempering process, adopts the ausforming process, ensures that the microscopic structure of finished steel plates becomes fine low-carbon tempered martensite and the average colony size is smaller than 20 micrometers, obtains ultra-high strength steel plates with good low-temperature flexibility, weldability and anti-delay cracks, solves the problem of overquenching of superficial layers of the ultra-high strength steel plates, and is particularly applicable to equipment manufacturing industries of large-scale engineering machinery and the like.

Description

technical field [0001] The present invention relates to a thick steel plate for engineering machinery, in particular to an ultra-high-strength steel for engineering machinery with excellent performance and a manufacturing method thereof. ≥34J, elongation at break δ 5 ≥10%, and has excellent welding performance. Background technique [0002] As we all know, low-carbon (high-strength) low-alloy steel is one of the most important engineering structural materials, widely used in oil and gas pipelines, offshore platforms, shipbuilding, bridge structures, boiler containers, building structures, automobile industry, railway transportation and engineering machinery manufacturing Among them; the properties of low-carbon (high-strength) low-alloy steel depend on its chemical composition and manufacturing process, among which strength, toughness, plasticity and weldability are the most important properties of low-carbon (high-strength) low-alloy steel, which are ultimately determined ...

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Problems solved by technology

[0006] In addition, the high sensitivity to environmental brittleness and low temperature toughness have a great influence on the fatigue resistance, stress concentration resistance, delayed crack resistance, crack resistance and structural stability of the steel plate. When used on large engineering machinery structures, there are Therefore, when ultra-high-strength steel is used for large-scale fatigue and heavy-duty steel structures, it is generally expected that high-strength steel above 1000 MPa not only has excellent strength, toughness, strong plasticity matching, and weldability, but also has excellent delayed crack resistance. Ensure the safety and reliability of large construction machinery during operation

A large number of existing patents and technical documents only explain how to realize the strength and low-temperature toughness of the base steel plate, improve the weldability of the steel plate, and obtain excellent welding heat-affected zone HAZ low-temperature toughness. At the same time, it improves the delayed crack resistance of the steel plate, and does not point out how to prevent the surface (sub) surface layer of the ultra-high-strength steel plate from being over-quenched. Patent US Patent5798004, European Patent EP 0288054A2, "Xishan Memorial Technology Lecture" No. 159-160, P79~P80, etc.

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