A large-thickness high-strength steel plate with a lamellar tear resistance yield strength of 960mpa and its production method

Abstract

The invention relates to a large-thickness lamellar tearing resistant high-strength steel plate with a yield strength of 960 MPa and a production method thereof. Its chemical composition contains: C: 0.15-0.20%, Si: 0.10-0.40%, Mn: 0.90~1.30%, Nb: 0.010~0.040%, V: 0.010~0.045%, Ti: ≤0.010%, Al: 0.03~0.06%, Ni: 0.50~1.00%, Cu: ≤0.1%, Cr: 0.30~0.80 %, Mo: 0.20~0.70%, B: 0.001~0.005%, Ca: 0.001~0.005%, P: ≤0.010%, S: ≤0.002%, O: ≤0.002%, N: ≤0.004%, H: ≤ 0.00015%, the balance is Fe and unavoidable impurity elements. The process steps are: smelting->external refining->vacuum degassing->Ca treatment->continuous casting->heating->rolling->slow cooling of steel plate->quenching->tempering. The steel plate of the present invention has excellent comprehensive mechanical properties, yield strength ≥ 960MPa, tensile strength ≥ 1000MPa, low-temperature Charpy impact energy ≥ 30J at -40°C, Z-direction tensile section reduction rate ≥ 35%, and lamellar tear resistance good.

Description

technical field [0001] The invention belongs to the field of iron and steel metallurgy, and in particular relates to a large-thickness high-strength steel plate with a lamellar tear resistance yield strength of 960 MPa and a production method thereof. Background technique [0002] High-strength steel plates with a yield strength of 960MPa and above are mainly used in key stress-bearing parts of construction machinery such as booms of construction cranes, pull plates of crawler cranes, and concrete pump trucks. The current dosage is mainly thin-gauge steel plates of 50mm and below. The limit specification of 960MPa high-strength steel in European standard EN10025-6 and national standard GB / T 16270 is also 50mm. With the gradual development of large-scale construction machinery and equipment at home and abroad, the demand for high-strength steel plates with a large thickness (≥50mm) yield strength of 960MPa and above is also increasing. [0003] As the thickness increases to...

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Problems solved by technology

[0003] As the thickness increases to more than 50mm, it will inevitably bring the following problems: (1) Limited by the quenching capacity of the quenching machine, there is a large gap between the mechanical properties of the surface of the steel plate and the core, and the performance of the steel plate in the thickness direction (Z direction) deteriorates. (2) It is difficult to guarantee the low-temperature impact toughness of large-thickness steel plates; (3) In order to ensure the hardenability of steel plates, the alloy content must increase, resulting in a decline in weldability

The steel plate has good strength and toughness, and the sensitivity to welding cold cracking is reduced, but the online TMCP process will inevitably cause differences in the performance of the steel plate head, middle and tail

The uneven performance of the whole board has a great impact on the fatigue life and safety of key stress-bearing parts such as crane booms

Chinese patent CN100494451C adopts the online DQ+tempering process to produce ultra-high-strength steel plates above 960MPa. It also faces the problem of uniformity of the entire plate, and its application will be limited to a certain extent.

These technologies mainly focus on the solution of strength-toughness matching and welding performance of thin steel plates, and do not involve the manufacturing technology of large-thickness steel plates ≥ 50 mm, and the control technology of Z-direction performance of steel plate thickness brought about by large thickness

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