A steel comprising 0.07 to 0.14 wt. % of carbon, 13 to 15 wt. % of chromium, 1.3 to 1.7 wt. % of molybdenum, 1.5 to 2.0 wt. % of nickel and 1.0 to 1.5 wt. % of manganese and use of the steel for producing screws is provided.

A steel comprising 0.07 to 0.14 wt. % of carbon, 13 to 15 wt. % of chromium, 1.3 to 1.7 wt. % of molybdenum, 1.5 to 2.0 wt. % of nickel and 1.0 to 1.5 wt. % of manganese and use of the steel for producing screws is provided.

A quench and temper steel alloy is disclosed having the following composition in weight percent.

TABLE-US-00001 C 0.1-0.4 Mn 0.1-1.0 Si 0.1-1.2 Cr 9.0-12.5 Ni 3.0-4.3 Mo 1-2 Cu 0.1-1.0 Co 1-4 W 0.2 max. V 0.1-0.6 Ti 0.1 max. Nb up to 0.01 Ta up to 0.01 Al 0-0.25 N 0.1-0.35 Ce 0.006 max. La 0.006 max.
The balance of the alloy is iron and the usual impurities found in similar grades of quench and temper steels intended for similar use or service, including not more than about 0.01% phosphorus and not more than about 0.010% sulfur. A quenched and tempered steel article made from this alloy is also disclosed. Further disclosed is a method of making the alloy.

A martensitic stainless steel containing, by mass %, C: 0.20% to 0.40%, N: 0.1% or less, Mo: 3% or less, and Cr: 12.0% to 16.0%, such that 0.3%C+N0.4% and a PI value (=Cr+3.3Mo+16N) is 18 or more, with the remainder being substantially Fe and unavoidable impurities is quenched from a temperature of 1,030 C. to 1,140 C. and subjected to a subzero treatment and tempering so as to obtain a prior austenite crystal grain size of a surface layer of 30 m to 100 m and a surface hardness of 58 HRc to 62 HRc.

A martensitic stainless steel containing, by mass %, C: 0.20% to 0.40%, N: 0.1% or less, Mo: 3% or less, and Cr: 12.0% to 16.0%, such that 0.3%C+N0.4% and a PI value (=Cr+3.3Mo+16N) is 18 or more, with the remainder being substantially Fe and unavoidable impurities is quenched from a temperature of 1,030 C. to 1,140 C. and subjected to a subzero treatment and tempering so as to obtain a prior austenite crystal grain size of a surface layer of 30 m to 100 m and a surface hardness of 58 HRc to 62 HRc.

A method for manufacturing a golf club head includes providing a club head body produced by electric smelting an alloy base material including 0.04-0.07 wt % of carbon, 0.5-1.0 wt % of manganese, 0.5-1.0 wt % of silicon, less than 0.04 wt % of phosphorus, less than 0.03 wt % of sulfur, 15-17.7 wt % of chromium, 3.6-5.1 wt % of nickel, 2.8-3.5 wt % of copper, with the rest being iron and inevitable impurities. A solid solution treatment is proceeded at 1020-1080 C. for 80-100 minutes to form austenite and martensite in the club head body. A deep cooling treatment is proceeded between 120 C. and 80 C. for 7-9 hours to turn the austenite in the club head body into martensite. An aging treatment is proceeded on the club head body at 460-500 C. for 210-270 minutes to provide a hardness of HRC 36-46. A hosel is heated with high frequency waves at 900-1000 C. to posses a hardness lower than HRC 20.

A method for manufacturing a golf club head includes providing a club head body produced by electric smelting an alloy base material including 0.04-0.07 wt % of carbon, 0.5-1.0 wt % of manganese, 0.5-1.0 wt % of silicon, less than 0.04 wt % of phosphorus, less than 0.03 wt % of sulfur, 15-17.7 wt % of chromium, 3.6-5.1 wt % of nickel, 2.8-3.5 wt % of copper, with the rest being iron and inevitable impurities. A solid solution treatment is proceeded at 1020-1080 C. for 80-100 minutes to form austenite and martensite in the club head body. A deep cooling treatment is proceeded between 120 C. and 80 C. for 7-9 hours to turn the austenite in the club head body into martensite. An aging treatment is proceeded on the club head body at 460-500 C. for 210-270 minutes to provide a hardness of HRC 36-46. A hosel is heated with high frequency waves at 900-1000 C. to posses a hardness lower than HRC 20.

According to the invention, a metal workpiece made by additive manufacturing is subjected, following the additive manufacturing process, to a cold treatment in which the workpiece is cooled to a lower target temperature of less than minus 30? C. in a cooling phase and is then heated up to an upper target temperature in a heating phase. The cold treatment significantly improves the properties of the workpiece in respect of the mechanical quality thereof.

According to the invention, a metal workpiece made by additive manufacturing is subjected, following the additive manufacturing process, to a cold treatment in which the workpiece is cooled to a lower target temperature of less than minus 30? C. in a cooling phase and is then heated up to an upper target temperature in a heating phase. The cold treatment significantly improves the properties of the workpiece in respect of the mechanical quality thereof.

A quench and temper steel alloy is disclosed having the following composition in weight percent. TABLE-US-00001 C 0.2-0.5 Mn 0.1-1.0 Si 0.1-1.2 Cr 9-14.5 Ni 2.0-5.5 Mo 1-2 Cu 0-1.0 Co 1-4 W 0.2 max. V 0.1-1.0 Ti up to 0.5 Nb 0-0.5 Ta 0-0.5 Al 0-0.25 Ce 0-0.01 La 0-0.01
The balance of the alloy is iron and the usual impurities including not more than about 0.01% phosphorus, not more than about 0.010% sulful, and not more than about 0.10% nitrogen. A quenched and tempered steel article made from this alloy is also disclosed. The steel article is characterized by a tensile strength of at least about 290 ksi, a fracture toughness (k.sub.Ic) of at least about 65 ksi, good resistance to general corrosion, and good resistance to pitting corrosion.