Pipe line steel for high linear energy welding and manufacturing method thereof

Abstract

The invention provides pipe line steel for high linear energy welding and a manufacturing method thereof. The pipe line steel for the high linear energy welding comprises the following components in percentage by weight: 0.05 to 0.08 percent of carbon, 0.15 to 0.35 percent of silicon, 1.5 to 1.8 percent of manganese, 0.004 to 0.006 percent of nitrogen, 0.012 to 0.016 percent of titanium, 0.02 to 0.04 percent of aluminum, 0.05 to 0.08 percent of rare earth elements, 0.03 to 0.07 percent of niobium, 0.2 to 0.4 percent of nickel, 0.2 to 0.5 percent of copper, not more than 0.010 percent of phosphorus, not more than 0.005 percent of sulfur, not more than 0.002 percent of oxygen and the balance of Fe and other inevitable impurity elements, wherein the weight ratio of the titanium to the nitrogen is controlled to be between 2 and 4, the weight ratio of the aluminum to the nitrogen is controlled to be between 3 and 10, and the yield strength Rt 0.2 of the pipe line steel for the high linear energy welding is more than 570 MPa. The pipe line steel has a typical needle-like ferritic structure, high comprehensive mechanical properties, high linear energy welding performance and low cost.

Description

Technical field [0001] The invention relates to the technical field of low-alloy high-strength steel, and more specifically, to a pipeline steel for large heat input welding and a manufacturing method thereof. Background technique [0002] X80 pipeline steel is a high-strength pipeline steel. Among them, X80 is an American classification model of high-strength pipeline steel, which means that the minimum yield strength of pipeline steel is 80,000 psi (approximately 552 MPa). [0003] With the continuous increase in the consumption of energy such as oil and natural gas, technological innovation of pipeline steel is also developing rapidly. Because of its high strength and high toughness, X80 pipeline steel has been used in the “West-East Gas Pipeline Second” gas pipeline project under construction and the backbone of the Sino-Russian oil pipeline project. Although there are many large and medium-sized steel mills that can manufacture X80 pipeline steel, although the traditional X80...

AI Technical Summary

Problems solved by technology

However, under the condition of large input energy welding, the traditional high-strength and high-toughness X80 pipeline steel has problems such as severe coarsening of grains in the coarse-grained heat-affected zone and changes in the structure during welding, which will lead to the formation of welded heat-affected zone. The performance does not match the performance of the pipeline steel parent material seriously, and the coarse-grained heat-affected zone of the welded joint no longer has many excellent properties of the pipeline steel

[0005] At present, in order to improve the performance of X80 grade pipeline steel under the condition of large input energy welding, and to improve the defect that the low-temperature impact toughness of the welded coarse-grained heat-affected zone is significantly reduced, some scholars believe that TiN precipitation is formed by adding Ti and N elements to molten steel. material to improve the toughness of the welded coarse-grained heat-affected zone, but the heating temperature of the welded coarse-grained heat-affected zone is very high (usually, higher than 1370°C) under the condition of large input energy welding, so TiN will dissolve