Abstract: The present invention relates to a heat-resistant cast steel that comprises, on a weight basis, 0.06-0.20% C, 0.01-0.10% N, 0.4-2.0% Si, 0.3-1.0% Mn, not more than 0.04% P, not more than 0.04% S, 15-22% Cr, 0.01-2.0% Nb, with the balance being Fe and incidental impurities, and further preferably that is retained at a temperature not higher than the temperature of two-phase mixed region for a certain time and then is gradually cooled, after casting;a heat-resistant cast steel that comprises, on a weight basis, 0.06-0.20% C, 0.01-0.10% N, 0.4-2.0% Si, 0.3-1.0% Mn, not more than 0.04% P, not more than 0.04% S, 15-22% Cr, 0.01-2.0% Nb, 0.2-1.0% Mo, with the balance being Fe and incidental impurities, and further preferably that is retained at a temperature not higher than the temperature of two-phase mixed region for a certain time and then is gradually cooled, after casting;a heat-resistant cast steel that comprises on a weight basis, 0.06-0.20% C, 0.01-0.10% N, 0.4-2.0% Si, 0.3-1.0% Mn, not more than 0.

Abstract: The present invention relates to a heat-resistant cast steel that comprises, on a weight basis, 0.06-0.20% C, 0.01-0.10% N, 0.4-2.0% Si, 0.3-1.0% Mn, not more that 0.04% P, not more than 0.04% S, 15-22% Cr, 0.01-2.0% Nb, with the balance being Fe and incidental impuriites, and further preferably that is retained at a temperature not higher than the temperature of two-phase mixed region for a cerain time and then is gradually cooled, after casting;A heat-resistant cast steel that comprises, on a weight basis, 0.06-0.20% C, 0.01-0.10% N, 0.4-2.0% Si, 0.3-1.0% Mn, not more than 0.04% P, not more than 0.04% S, 15-22% Cr, 0.01-2.0% Nb, 0.2-1.0% Mo, with the balance being Fe and incidental impurities, and further preferably that is retained at a temperature not higher than the temperature of two-phase mixed region for a certain time and then is gradually cooled, after casting;A heat-resistant cast steel that comprises, on a weight basis, 0.06-0.20% C, 0.01-0.10% N, 0.4-2.0% Si, 0.3-1.0% Mn, not more than 0.

Abstract: An exhaust manifold is, which includes a plurality of steel members having the same metallic crystal structure in a range of working temperature, which are jointed with each other by permanent welding and spot welding at different places, wherein material for the spot welding is a material having a different metallic crystal structure than that of the steel members.

Abstract: A case hardening steel which consists essentially of 0.03-0.2 wt % of C, 1.0-3.0 wt % of Si, 0.2-2.0 wt % of Mn, 0.05-0.5 wt % of V and the balance of Fe. The primary advantage of this steel is fineness of grain size after carburizing at relatively high temperatures. Even when carburizeed at or above 950.degree. C., the grain size number is not smaller than 6 in both the hardened case and the core. Optionally the steel may contain up to 2.0 wt % of Ni, up to 2.0 wt % of Cr and/or up to 0.5 wt % of Mo for the reinforcing purpose, and/or up to 0.1 wt % of Al, up to 0.3 wt % of Ti, up to 0.1 wt % of Zr, up to 0.03 wt % of N and/or up to 0.5 wt % of Nb+Ta for the purpose of depressing the grain growth.

Abstract: Gears are formed from annular blanks in a gear-forming apparatus including a die block formed with an axial bore and teeth radially projecting into the bore, a cylindrical punch sleeve axially movable toward and away from the bore in the die block, a mandrel movable with the punch sleeve into and out of the bore in the die block, and a backup sleeve axially movable into and out of the bore in the die block in opposite directions to the directions of movement of the sleeve punch and mandrel, wherein gears are formed by preliminarily forcing at least one of the blanks into the bore in the die block until the blank is partially deformed by the teeth of the die block; placing another blank on the preceding blank so that the subsequent blank is received on the preceding blank; causing the mandrel to extend through the respective center holes in the preceding and subsequent blanks; pressing the preceding and subsequent blanks between the end faces of the punch and backup sleeve and forcing the two blanks through th