TH59983A - Welded steel pipes with excellent hydrogen transformation capabilities and manufacturing methods. - Google Patents

Abstract

DC60 (24/06/45) welded steel pipes are manufactured by hot or immersion welding of untreated welded steel pipes containing, on the basis of mass percentages: approximately 0.03% to approximately 0.2% carbon, approximately 2.0% or less of silicon, not less than approximately 1.0% to approximately 1.5% of manganese, approximately 0.1% or less of phosphorus, approximately 0.01% or less of sulfur, approximately 1.0% or less of chromium, approximately 0.1% or less of aluminum, approximately 0.1% or less of niobium, approximately 0.1% or less of titanium, approximately 0.1% or less of vanadium, and approximately 0.01% or less of nitrogen, and by rolling or reducing the treated steel pipes. At a minimum cumulative reduction rate of approximately 35% and a final rolling temperature of approximately 500°C to approximately 900°C, welded steel pipes exhibit excellent hydrogen deformation capabilities, i.e., tensile strength of at least approximately 590 MPa and an n x r product 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 Ar3 transition point. Welded steel pipes are also formed by hot-dip or immersion welding untreated welded steel pipes containing steel alloys with, based on mass percentages, approximately 0.03% to approximately 0.2% carbon and approximately 2.0% or less of... Silicon, not less than approximately 1.0% to approximately 1.5% manganese, approximately 0.1% or less of phosphorus, approximately 0.01% or less of sulfur, approximately 1.0% or less of chromium, approximately 0.1% or less of aluminum, approximately 0.1% or less of niobium, approximately 0.1% or less of nitrogen, and by rolling reduction, the steel pipes are processed at a cumulative reduction rate of at least approximately 35% and a final rolling temperature of approximately 500°C to approximately 900°C. The welded steel pipes have excellent hydrogen deformation capabilities, such as a tensile strength of at least approximately approximately 590 MPa and an n x r product of at least approximately approximately 0.22. The processed steel pipes are suitable for reduction rolling at a cumulative reduction rate of at least approximately approximately 20% below the Ar3 transition point.

Claims (11)

1. Welded steel pipes with excellent hydrogenation capability, composed of, based on mass percentages, approximately 0.03% to 0.2% carbon, approximately 0.01% to 2.0% silicon, approximately 1.0% to 1.5% manganese, approximately 0.01% to 0.01% phosphorus, approximately 0.01% or less sulfur, approximately 0.01% to 1.0% chromium, approximately 0.01% to 0.1% aluminum, approximately 0.01% to 0.1% niopium, approximately 0.01% to 0.1% titanium, approximately 0.01% to 0.1% vanadium, approximately 0.001% to 0.01% nitrogen, and the remainder being iron and any other impurities. Where welded steel pipes have a tensile strength of at least approximately 590 MPa and the n x r product of n and r values 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 group of Group A and Group B where Group A contains at least one element of 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 elements. 4. The welded steel pipes under claim 2 also contain at least one group of Group A and Group B where Group A contains at least one element of 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 approximately 780 Mpa. 6. A method for making weldable steel pipes with excellent hydrogen deformation capabilities involves heating or immersing the untreated weldable steel pipe containing a steel component, on a basis... The percentage by mass of carbon is approximately 0.03% to 0.2%, silicon approximately 0.2% or less, manganese approximately 1.0% to 1.5%, phosphorus approximately 0.1% or less, sulfur approximately 0.01% or less, niobium approximately 1.0% or less, titanium approximately 0.1% or less, vanadium approximately 0.01% or less, and nitrogen approximately 0.01% or less. The steel pipes are then rolled at a reduction rate of at least 35% and a final rolling temperature of approximately 500°C to 900°C, in such a way that the welded steel pipes have a tensile strength of at least 590 MPa and an n x r product of at least 0.22. 7. Method for the production of welded steel pipes according to claim 6, where the treated steel pipes are subjected to a 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 group of Group A and Group B, where Group A contains at least one element of 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 elements. 9. The method for making welded steel pipes according to claim 7 also includes at least one element of Group A and Group B, where Group A contains at least one element of 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 elements. 10. Method for fabricating 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 approximately 90%.