Heat-resistant steel for steel pipes and castings

Abstract

The present invention provides an element composition and use of a heat-resistant steel for steel pipes and castings. The present invention further provides a preparation method and use of a steel pipe and a casting. The heat-resistant steel for steel pipes and castings provided by the present invention according to preferred element composition can be used to prepare the heat-resistant steel pipe and the casting with excellent properties through the preparation steps thereof. The steel pipe and the casting prepared from this heat-resistant steel have excellent creep rupture strength, and can satisfy the use requirements of pressure vessels or parts of power machinery with a working temperature of 650° C. and below 650° C.

1 - 12 . (canceled) 
     
     
         13 . A heat-resistant steel, comprising the following elements in mass percentage:
 0.08-0.14 wt % of C, 0.20-0.40 wt % of Si, 0.30-0.60 wt % of Mn, <0.020 wt % of P, <0.010 wt % of S, 9.00-10.00 wt % of Cr, 2.80-3.30 wt % of Co, 1.65-1.90 wt % of W, 0.55-0.80 wt % of Mo, 0.15-0.25 wt % of V, 0.03-0.08 wt % of Nb, 0.006-0.015 wt % of N, 0.009-0.015 wt % of B, <0.20 wt % of Ni, <0.02 wt % of Al, <0.02 wt % of Ti, <0.02 wt % of Zr, <0.15 wt % of Cu, <0.02 wt % of Sn, <0.02 wt % of As, <0.005 wt % of Sb and the balance of Fe   wherein a Cr equivalent is <8.5% based on Cr+6Si+4Mo+1.5W+11V+5Nb-40C-2Mn-4Ni-2Co-30N, and a mass ratio of B to N is 0.65-2.40:1.   
     
     
         14 . The heat-resistant steel according to  claim 13 , wherein the heat-resistant steel comprises the following elements in mass percentage:
 0.08-0.13 wt % of C, 0.20-0.30 wt % of Si, 0.40-0.50 wt % of Mn, <0.020 wt % of P, <0.005 wt % of S, 9.00-9.60 wt % of Cr, 2.90-3.20 wt % of Co, 1.70-1.85 wt % of W, 0.60-0.75 wt % of Mo, 0.18-0.25 wt % of V, 0.04-0.07 wt % of Nb, 0.007-0.014 wt % of N, 0.010-0.015 wt % of B, <0.10 wt % of Ni, <0.01 wt % of Al, <0.01 wt % of Ti, <0.01 wt % of Zr, <0.10 wt % of Cu, <0.01 wt % of Sn, <0.01 wt % of As, <0.003 wt % of Sb and the balance of Fe,   wherein a Cr equivalent is <8.0% based on Cr+6Si+4Mo+1.5W+11V+5Nb-40C-2Mn-4Ni-2Co-30N, and a mass ratio of B to N is 0.75-2.10:1.   
     
     
         15 . A method of preparing a steel pipe, comprising:
 mixing raw materials according to mass percentage element proportioning of heat-resistant steel as follows:
 0.08-0.14 wt % of C, 0.20-0.40 wt % of Si, 0.30-0.60 wt % of Mn, <0.020 wt % of P, <0.010 wt % of S, 9.00-10.00 wt % of Cr, 2.80-3.30 wt % of Co, 1.65-1.90 wt % of W, 0.55-0.80wt % of Mo, 0.15-0.25 wt % of V, 0.03-0.08 wt % of Nb, 0.006-0.015 wt % of N, 0.009-0.015 wt % of B, <0.20 wt % of Ni, <0.02 wt % of Al, <0.02 wt % of Ti, <0.02 wt % of Zr, <0.15 wt % of Cu, <0.02 wt % of Sn, <0.02 wt % of As, <0.005 wt % of Sb and the balance of Fe 
 wherein a Cr equivalent is <8.5% based on Cr+6Si+4Mo+1.5W+11V+5Nb-40C-2Mn-4Ni-2Co-30N, and a mass ratio of B to N is 0.65-2.40:1; 
 smelting the mixed raw materials; 
 making a pipe blank by any one of continuous casting, die casting, hot rolling or hot forging of the smelted mixed raw materials; 
 making the pipe blank into a steel pipe by any one of hot rolling, hot extrusion, hot expansion, cold drawing, cold rolling, or forging and boring of the pipe blank; 
 normalizing or quenching the steel pipe; and 
 tempering the steel pipe, 
 wherein the normalizing or quenching is carried out at a temperature of 1070-1160° C.; and the tempering is carried out at least one time, and the tempering is carried out at a temperature of 740-790° C. 
   
     
     
         16 . A method of preparing a casting, comprising:
 mixing raw materials according to mass percentage element proportioning of heat-resistant steel as follows:
 0.08-0.14 wt % of C, 0.20-0.40 wt % of Si, 0.30-0.60 wt % of Mn, <0.020 wt % of P, <0.010 wt % of S, 9.00-10.00 wt % of Cr, 2.80-3.30 wt % of Co, 1.65-1.90 wt % of W, 0.55-0.80 wt % of Mo, 0.15-0.25 wt % of V, 0.03-0.08 wt % of Nb, 0.006-0.015 wt % of N, 0.009-0.015 wt % of B, <0.20 wt % of Ni, <0.02 wt % of Al, <0.02 wt % of Ti, <0.02 wt % of Zr, <0.15 wt % of Cu, <0.02 wt % of Sn, <0.02 wt % of As, <0.005 wt % of Sb and the balance of Fe 
 wherein a Cr equivalent is <8.5% based on Cr+6Si+4Mo+1.5W+11V+5Nb-40C-2Mn-4Ni-2Co-30N, and a mass ratio of B to N is 0.65-2.40:1; 
 smelting and pouring the mixed raw materials to obtain a casting; 
 normalizing or quenching the casting, and 
 tempering the casting, 
 wherein the normalizing or quenching is carried out at a temperature of 1070-1160° C.; and the tempering is carried out at least one time, and the tempering is carried out at a temperature of 730-780° C. 
   
     
     
         17 . Use of the heat-resistant steel according to  claim 13  in a pressure vessel. 
     
     
         18 . Use of the steel pipe prepared in accordance with  claim 15  in a pressure vessel. 
     
     
         19 . Use of the heat-resistant steel according to  claim 13  in power machinery. 
     
     
         20 . Use of the casting prepared in accordance with  claim 16  in a pressure vessel.