C - Chemistry – Metallurgy – 21 – C
Patent
C - Chemistry, Metallurgy
21
C
C21C 7/064 (2006.01) C21C 7/00 (2006.01) C21C 7/04 (2006.01) C21C 7/06 (2006.01) C21C 7/10 (2006.01) C22C 38/00 (2006.01) C22C 38/14 (2006.01) C22C 38/58 (2006.01)
Patent
CA 2689522
The steel for steel pipes of the present invention is the one for steel pipes excellent in sour-resistance performance including C, Mn, Si, P, S, Ti, Al, Ca, N and O, and optionally including a predetermined amount of one or more of Cr, Ni, Cu, Mo, V, B and Nb, in which inclusions in the steel have Ca, Al, O and S as main components, the CaO content in the inclusions is 30 to 80%, the ratio of the N content in the steel (ppm) to the CaO content in the inclusions (%) is from 0.28 to 2.0, and the CaS content in the inclusions is 25% or less. In addition, the method of producing steel for steel pipes of the present invention is to produce steel for steel pipes in which Ca is added so that the ratio of the N content in the steel to the amount of Ca addition (kg/t) into the molten steel is from 200 to 857. According to the production method of the present invention, a slag composition, temperature-raising heating of molten steel, stirring treatment of molten steel and slag, and the Ca addition are optimized, whereby high-strength HIC resistant steel for steel pipes that exhibit excellent sour-resistance performance and cleanliness can be stably manufactured.
L'invention concerne un acier, destiné à des tuyaux en acier qui présentent une excellente résistance à l'acidité, contenant C, Mn, Si, P, S, Ti, Al, Ca, N, O et, si nécessaire, un ou plusieurs éléments parmi Cr, Ni, Cu, Mo, V, B et Nb dans des quantités prescrites, l'inclusion de l'acier comprenant Ca, Al, O et S en tant que composants principaux, et la teneur en CaO de l'inclusion étant de 30 à 80%, le rapport entre la teneur en N (ppm) de l'acier et la teneur en CaO (%) de l'inclusion étant de l'ordre de 0,28 à 2,0 et la teneur en CaS de l'inclusion étant de 25% ou moins. L'invention concerne également un procédé de fabrication de l'acier destiné à des tuyaux en acier qui comprend l'ajout de Ca afin que le rapport entre la teneur en N (ppm) de l'acier et la quantité (kg/t) de Ca ajoutée à l'acier liquide soit de l'ordre de 200 à 857. Le procédé peut optimiser la composition du laitier, l'augmentation de température de l'acier liquide, le mélange de l'acier liquide et du laitier, et l'ajout de Ca, et permettre ainsi une production stable d'acier à haute résistance et qui résiste aux HIC pour des tuyaux en acier qui présentent une excellente résistance à l'acidité et une excellente pureté.
Numata Mitsuhiro
Omura Tomohiko
Takeuchi Shingo
Gowling Lafleur Henderson Llp
Sumitomo Metal Industries Ltd.
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