Tensile strength-700MPa level easy-to-weld low-internal-stress structural steel plate and manufacturing method thereof

Abstract

The invention discloses a tensile strength-700MPa level easy-to-weld and low-internal-stress structural steel plate, prepared from the following chemical components according to mass percent: 0.04 to 0.09 percent of C, 0.20 to 0.48 percent of Si, 1.40 to 1.70 percent of Mn, not more than 0.30 percent of Cr, 0.020 to 0.045 percent of Nb, 0.012 to 0.020 percent of Ti, 0.005 to 0.030 percent of V, 0.020 to 0.038 percent of Als, 0.0012 to 0.0028 percent of B, less than 0.015 percent of P, less than 0.006 percent of S, not more than 0.0060 percent of [N], and the balance of Fe and inevitable impurities. The invention also provides a manufacturing method of the tensile strength-700MPa level easy-to-weld and low-internal-stress structural steel plate. The steel plate is simple in chemical component, and has excellent low-temperature toughness and a Pcm not more than 0.20 percent; the expensive alloying elements such as Mo, Cu and Ni are not added, and adding new equipment is also not needed, and the performance of the steel plate produced by controlled rolling and controlled cooling as well as stress removal processing can completely meet the relevant requirements of national standards.

Description

technical field [0001] The invention relates to the field of low-alloy high-strength steel production, in particular to an easy-to-weld low internal stress structural steel plate with a tensile strength of 700 MPa and a manufacturing method thereof. Background technique [0002] With the rapid development of energy, chemical industry, construction and other fields, the market demand for low-alloy high-strength structural steel is increasing day by day, and in order to meet the development trend of reducing the self-weight of engineering structures and improving loading capacity in the above industries, steel plates with a tensile strength of 700MPa (brand Q550) is used more and more. Steel plates of this strength level were produced in the way of quenching + tempering (quenching and tempering) after rolling in the early days. This production method not only leads to poor welding performance due to high carbon content and carbon equivalent, but also has a long production cycl...

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Problems solved by technology

According to GB / T1591-2008, the welding crack sensitivity index Pcm[Pcm=C+Mn / 6+(Cr+Mo+V) / 5+(Ni+Cu) / 15] can be used to evaluate the weldability of steel, The lower the Pcm value, the better the welding performance of the steel plate. After welding, cold cracks are less likely to appear at the welded joints. Large cooling rate, which is often said "replace gold with water", but during the rapid cooling process, there is a large internal stress inside the steel plate. During the subsequent use of the user, especially when cutting, the steel plate is prone to deformation. On the one hand, the size of the steel plate If it is out of tolerance, it will affect the use; on the other hand, the deformed steel plate will damage the cutting equipment and cause accidents

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