Manufacturing method of super-thick steel plate

Abstract

The invention discloses a manufacturing method of a super-thick steel plate (thickness is 60 millimeters) and belongs to the steel plate production field of metallurgical industry. The manufacturing method of the super-thick steel plate comprises the following steps: firstly, sending a plate blank which is heated to a certain temperature and removed an oxide scale to cooling space to conduct forced cooling, surface temperature cooling a phase transition temperature of the super-thick plate material above Ar 1, then by short time temperature returning, the surface temperature rising to the range between 780 DEG C and 880 DEG C, and sending the plate bland to a rolling mill to roll as soon as possible; when the surface temperature of the plate blank being higher than 880 DEG C, needing to conduct the forced cooling again, and then conducting the subsequent rolling. A cooling-temperature returning-rolling process can be repeated for many times if needed till rolling to the needed thickness of the super-thick steel plate. The manufacturing method of a super-thick steel plate can increase dependent variable of the central area by increasing temperature difference between a surface layer and the central area and has the advantages of being beneficial to refining central organization and improving impact toughness, beneficial to removing center porosity of the super-thick plate, and capable of reducing double strand shape on lateral sides of the super-thick plates. The manufacturing method of a super-thick steel plate further has the advantages of being saving in investment, and flexible to operate.

Description

technical field [0001] The invention belongs to the field of steel plate production in the metallurgical industry, and relates to a method for manufacturing an extra-thick plate with a thickness ≥ 60mm, aiming at solving the problem of low mechanical properties at the center of the rolled extra-thick plate, and the double-drum shape of the side of the steel plate during the rolling process. Edge folding problem caused by further rolling with double drum type. [0002] Background technique [0003] Under the requirements of large-scale and high-efficiency construction, a large single-weight, extra-wide, and extra-thick steel plate can reduce weld seams. In the construction of offshore platforms, high-strength and large-thickness steels are widely used, especially for structures such as lifting points, which require a thickness of 80mm; the steel used for racks in jack-up platform structures requires a yield strength level of 690MPa and a thickness of 80mm. 110~150mm. High-...

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Problems solved by technology

[0009]4) Continuous casting slab rolling-heat treatment process: Chinese patent application CN 101831526A "A processing method for extra-thick plate" and literature "High-strength low-alloy STE460 special "Thick Plate Production Test Research" ("Wide and Heavy Plate", Issue 05, 1999) introduced the method of producing high-performance extra-thick plate by normalizing after rolling and accelerated cooling after normalizing. This method can effectively improve the quality of extra-thick plate. Low-temperature toughness, but results in reduced strength and high production costs

The remaining area in the thickness direction is not deformed, resulting in a "double drum" shape on the side of the rolled billet, such as Figure 2, if this shape is maintained until the finished product, it will reduce the yield of the blank

At the same time, the uneven deformation in the thickness direction will form compressive stress in the rolling direction in the hc thickness region of the surface layer, and tensile stress in the rolling direction will be generated in the middle, which will deteriorate the stress state in the middle

In some methods, the rolling of the vertical roller mill is used to partially eliminate the "double drum" shape, but the large width-thickness ratio of the extra-thick plate cannot be effectively improved without deformation or small deformation in the central area, so that the thermal deformation can improve the structure and performance. The effect is limited, so in the undeformed or small deformed central area, the deformation recrystallization, elimination of segregation, and reduction of porosity are far worse than those of the surface layer of the billet.

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