Low-temperature steel for engineering machinery and production method thereof

Abstract

The invention relates to low-temperature steel for engineering machinery and a production method thereof. The steel is suitable for higher heat input welding and comprises the following chemical components by weight percent: 0.06-0.08% of C, 0.15-0.25% of Si, 1.6-1.9% of Mn, 0.05-0.07% of Nb, 0-0.30% of Mo, 0-0.0020% of B, 0.08-0.14% of Ti, 0.01-0.06% of Al, not more than 0.02% of P, not more than 0.010% of S, not more than 0.008% of N and the balance of Fe and inevitable impurities. The production method is characterized by controlling the heating temperature, precision rolling inlet temperature, finish rolling temperature, finished cooling temperature and annealing temperature. The material can ensure the transverse universal coiling impact energy at minus 20 DEG C to be more than 47J, and meanwhile, the HAZ (heat affected zone) strength and toughness of the steel plate can meet the mechanical property requirements of the base metal under 20KJ/cm welding property energy.

Description

technical field [0001] The invention belongs to the technical field of steel material production, and relates to steel for low-temperature construction machinery and a production method thereof, in particular to steel for low-temperature construction machinery with a yield strength of 600MPa and 700MPa and a production method thereof. By strictly controlling the rolling process, the base metal has excellent strength and toughness matching, and the material can maintain high strength, low temperature impact toughness and cold bending performance under the condition of large input energy welding. Background technique [0002] 600MPa and 700MPa construction machinery steels have been widely used in the manufacture of automobile crane booms and concrete pump truck arms. More and more stringent requirements have been put forward. For example, the 700MPa D-grade steel plate requires the yield strength of the base metal to be greater than 700MPa, while ensuring that the impact ene...

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Problems solved by technology

[0005] In the prior art, the patented technology related to the production method of 600MPa and 700MPa high-strength steel for construction machinery, such as patent application No. The low temperature impact toughness of the material is not intentionally controlled and elaborated, and it is difficult to guarantee the welding performance of the material

Patent application number 201010237136.6 introduces a production method of 600MPa high-strength steel by hot continuous rolling. The disadvantage is that it is difficult to guarantee the mechanical properties of the hot zone when welding with large input energy

Patent application No. 200910010662.6 introduces a production method of 600MPa high-strength steel based on Ti strengthening. The strength is increased by adding a small amount of B. However, the patent uses a high rolling temperature, which results in poor rolling control and low-temperature impact toughness is difficult to guarantee. , while not testing and describing the welding performance of the material

Among the patents related to the production method of 700MPa high-strength steel, for example, patent application number 200910083635.1 introduces a method of producing high-strength steel with a yield strength of 700MPa by Nb-Ti-V microalloying. Low temperature impact toughness and weldability

[0007] (1) The welding performance of the material is ignored in the chemical composition design and production process design, especially under the condition of large input energy welding, it is difficult to guarantee the performance of the material to meet the standard requirements of the base metal, resulting in potential safety hazards;

[0008] (2) The low-temperature impact toughness of the material is not strictly controlled from the perspective of controlling the production process, such as the transverse low-temperature impact toughness of the material is difficult to meet the requirements of D-grade steel plates;

[0009] (3) The shape quality of the high-strength steel flat plate is not controlled by technological means, and it is difficult for the steel plate to guarantee the shape requirements of the user after blanking during use

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