TH59984A - Welded steel pipes with excellent hydrogen transformation capabilities and the methods for manufacturing them. - Google Patents

Abstract

DC60 (24/06/45) welded steel pipes are manufactured by heating or immersing untreated welded steel pipes containing, on the basis of mass percentages: approximately 0.05% to approximately 0.2% carbon, approximately 0.2% or less of silicon, approximately 1.5% or less of manganese, approximately 0.1% or less of phosphorus, approximately 0.01% or less of sulfur, approximately 0.1% or less of aluminum, and approximately 0.01% or less of nitrogen, and by reduction rolling of treated steel pipes at a cumulative reduction rate of at least 35% and a final rolling temperature of approximately 500°C to approximately 900°C. Welded steel pipes are capable of hydrogenation. Excellent, for example, having a tensile strength of at least approximately 400 MPa and a product n x r of at least approximately 0.22, treated steel pipes are suitable for reduction rolling at a cumulative reduction rate of at least approximately 20% below the transition point Ar3. Welded steel pipes are suitable for fabricating structural components. Welded steel pipes are fabricated by heating or immersing untreated welded steel pipes containing steel alloys, based on mass percentages: approximately 0.05% to approximately 0.2% of carbon, approximately 0.2% or less of silicon, approximately 1.5% or less of manganese, approximately 0.1% or less of phosphorus, approximately 0.01% or less of sulfur, approximately 0.1% or less of aluminum, and approximately 0.01% or less of nitrogen, and by reduction rolling the treated steel pipes at a reduction rate of at least approximately 20% below the transition point Ar3. With a minimum accumulation of 35% and a final rolling temperature of approximately 500°C to 900°C, welded steel pipes exhibit excellent hydrogen deformation capabilities, such as tensile strength of at least approximately 400 MPa and a product n x r of at least approximately 0.22. Steel pipes treated with this process are suitable for reduction rolling at a minimum accumulation reduction rate of approximately 20% below the Ar3 transition point. Welded steel pipes are suitable for fabricating structural components.

Claims (11)

1. Welded steel pipes with excellent hydrogenation capability are composed of, on a mass percentage basis, approximately 0.05% to 0.2% carbon, approximately 0.01% to 0.2% silicon, approximately 0.2% to 1.5% manganese, approximately 0.01% to 0.1% phosphorus, approximately 0.01% or less of sulfur, approximately 0.01% to 0.1% aluminum, approximately 0.001% to 0.01% nitrogen, and the remainder being iron and impurities. These welded steel pipes possess exceptional tensile strength and toughness. The minimum is approximately 400 MPa, and the product n x r of the values of n and r is at least approximately 0.22. 2. Welded steel pipes pursuant to claim 1, where n is at least approximately 0.15 or r is at least approximately 1.5. 3. The welded steel pipes under claim 1 also contain at least one element selected from the Group A and Group B elements where Group A contains at least one element of approximately 0.1% or less of chromium, approximately 0.05% or less of niobium, approximately 0.05% or less of titanium, approximately 1.0% or less of copper, approximately 1.0% or less of nickel, approximately 1.0% or less of molybdenum, and approximately 0.01% or less of boron, and Group B contains at least one element of approximately 0.02% or less of calcium and approximately 0.02% or less of rare earth metals. 4. The welded steel pipes under claim 2 also contain at least one element selected from groups A and B, whereby group A contains at least one element of approximately 0.1% or less of chromium, approximately 0.05% or less of niobium, approximately 0.05% or less of titanium, approximately 1.0% or less of copper, approximately 1.0% or less of nickel, approximately 1.0% or less of molybdenum, and approximately 0.01% or less of boron, and group B contains at least one element of approximately 0.02% or less of calcium and approximately 0.02% or less of rare earth metals. 5. Welded steel pipes according to claim 1, where the tensile strength is between approximately 400 MPa and approximately 590 MPa. 6. The method for making welded steel pipes with excellent hydrogen deformation capabilities involves heating or immersing untreated welded steel pipes containing, based on mass percentages: approximately 0.05% to approximately 0.2% carbon, approximately 0.2% or less silicon, approximately 1.5% or less manganese, approximately 0.01% or less phosphorus, approximately 0.01% or less sulfur, approximately 0.1% or less aluminum, and approximately 0.01% or less nitrogen. The treated steel pipes are then rolled at a cumulative reduction rate of at least approximately 35% and a final rolling temperature of approximately 500°C to approximately 900°C, in such a way that the welded steel pipes exhibit excellent hydrogen deformation capabilities. The material has a tensile strength of at least approximately 400 MPa, and the product's n and r values are at least approximately 0.22. 7. Method for the production of welded steel pipes according to claim 6, in which the treated steel pipes are subjected to reduction rolling at a cumulative reduction rate of at least approximately 20% at a temperature below the transition point Ar3. 8. The method for producing welded steel pipes under claim 6 also includes at least one element selected from groups A and B, where group A contains at least one element of approximately 0.1% or less of chromium, approximately 0.05% or less of niobium, approximately 0.05% or less of titanium, approximately 1.0% or less of copper, approximately 1.0% or less of nickel, approximately 1.0% or less of molybdenum, and approximately 0.01% or less of boron, and group B contains at least one element of approximately 0.02% or less of calcium and approximately 0.02% or less of rare earth metals. 9. The method for producing welded steel pipes according to claim 7 also includes at least one element selected from groups A and B, where group A contains at least one element of approximately 0.1% or less of chromium, approximately 0.05% or less of niobium, approximately 0.05% or less of titanium, approximately 1.0% or less of copper, approximately 1.0% or less of nickel, approximately 1.0% or less of molybdenum, and approximately 0.01% or less of boron, and group B contains at least one element of approximately 0.02% or less of calcium and approximately 0.02% or less of rare earth metals. 10. Method for manufacturing welded steel pipes according to claim 6, where heating is done at approximately 700°C to approximately 1100°C. 11. Method for fabricating welded steel pipes according to claim 6 where the cumulative reduction rate reaches 90%.