A precipitation hardenable, martensitic stainless steel is disclosed. The alloy has the following broad composition in weight percent. TABLE-US-00001 Ni 10.5-12.5 Co 1.0-6.0 Mo 1.0-4.0 Ti 1.5-2.0 Cr  8.5-11.5 Al Up to 0.5 Mn  1.0 max. Si 0.75 max. B 0.01 max.
The balance of the alloy is iron and the usual impurities found in commercial grades of precipitation hardenable martensitic stainless steels as known to those skilled in the state of the art in melting practice for such steels. A method of making parts from the alloy and an article of manufacture made from the alloy are also described.

A method of making a forged, martensitic, stainless steel alloy is provided. The alloy is a forged preform of martensitic, pitting corrosion resistant stainless steel alloy comprising, by weight: 12.0 to 16.0 percent chromium; greater than 16.0 to 20.0 percent cobalt, 6.0 to 8.0 percent molybdenum, 1.0 to 3.0 percent nickel, 0.02 to 0.04 percent carbon; and the balance iron and incidental impurities. The alloy has a microstructure that comprises a retained austenite phase less than or equal to 2 percent by volume of the microstructure. The method heats the preform to a solutionizing temperature to form a solutionized microstructure. The preform is cooled with a liquid to room temperature. The preform is immersed in a cryo-liquid to transform the retained austenite phase in the microstructure to martensite. The preform is heated to a temperature of less than 600° F. for a time sufficient to form a tempered forged preform.

In a cryogenic workbench, a cryogenic laser peening system and a control method, a tapered surface gap d is adjusted, based on the electromagnetic principle, to control the gasification volume of liquid nitrogen, then the temperatures of the copious cooling workbench and the surface of a sample are precisely controlled by means of the adjustment of the heat absorption amount of liquid nitrogen gasification, the temperature adjustment range and the temperature rising/lowering rate of the cryogenic laser peening system are effectively extended, and the precision of the control of the surface temperature of the sample is increased in combination with a closed-loop control. Additionally, an intelligent control of a cryogenic laser peening process is realized by means of a computer and a PLC control unit, whereby the usage amount of liquid nitrogen in the experiment process is reduced and the processing efficiency is improved.

In a cryogenic workbench, a cryogenic laser peening system and a control method, a tapered surface gap d is adjusted, based on the electromagnetic principle, to control the gasification volume of liquid nitrogen, then the temperatures of the copious cooling workbench and the surface of a sample are precisely controlled by means of the adjustment of the heat absorption amount of liquid nitrogen gasification, the temperature adjustment range and the temperature rising/lowering rate of the cryogenic laser peening system are effectively extended, and the precision of the control of the surface temperature of the sample is increased in combination with a closed-loop control. Additionally, an intelligent control of a cryogenic laser peening process is realized by means of a computer and a PLC control unit, whereby the usage amount of liquid nitrogen in the experiment process is reduced and the processing efficiency is improved.

A duplex stainless steel and method of manufacturing the same, said steel having an amount of Cr in an extraction residue [Cr] of 0.005 to 0.050% and an amount of Nb in an extraction residue [Nb] of 0.001 to 0.080%, the [Nb]/[Cr] ratio being 0.2 or more. By slow cooling down to 800° C., then fast cooling down to 600° C., it is possible to control the precipitation of chromium nitrides and niobium nitrides, and by making the ratio [Nb]/[Cr] 0.2 or more, it is possible to raise the corrosion resistance. Further, by reducing Mn to less than 2.0% and N to 0.25% or less, then adding a trace amount of Nb, the effect of raising the critical pitting temperature CPT is obtained.

A duplex stainless steel and method of manufacturing the same, said steel having an amount of Cr in an extraction residue [Cr] of 0.005 to 0.050% and an amount of Nb in an extraction residue [Nb] of 0.001 to 0.080%, the [Nb]/[Cr] ratio being 0.2 or more. By slow cooling down to 800° C., then fast cooling down to 600° C., it is possible to control the precipitation of chromium nitrides and niobium nitrides, and by making the ratio [Nb]/[Cr] 0.2 or more, it is possible to raise the corrosion resistance. Further, by reducing Mn to less than 2.0% and N to 0.25% or less, then adding a trace amount of Nb, the effect of raising the critical pitting temperature CPT is obtained.

An example component of a machine includes a core layer and an outer layer encasing the core layer. The outer layer has a greater carbon concentration and hardness than the core layer. The outer layer may also be compressively stressed, while the core layer may have tensile stress. The stress and/or hardness profile of the component may enhance its resistance to cracking, particularly in applications where the component is impacted by other object and/or operates at elevated temperatures. The component, such as parts of a fuel injector, may be formed by rough forming the component, carburizing the component, quenching the component, subzero processing the component, and then performing a tempering process. The components may have relatively sharp transition from the high carbon outer layer to the lower carbon core layer. Additionally, the components have a relatively high tempering resistance when used in relatively high temperature environments.

Provided are: steel for knives, having a higher hardness and better corrosion resistance than conventional steel for knives; a knife; steel for martensitic knives; and a production method for same. The steel for knives comprises a component composition containing, in mass %, 0.45%-1.00% C, 0.1%-1.5% Si, 0.1%-1.5% Mn, 7.5%-11.0% Cr, and 0.5%-3.0% of either Mo or W or a complex of both (Mo+W/2), with the remainder being Fe and unavoidable impurities. Also provided are steel for martensitic knives and a knife. A production method for steel for martensitic knives is also provided that includes a quenching temperature at quenching of 1,050-1,250° C., a processing temperature for subzero processing of no more than −50° C., and a tempering temperature at tempering of 100-400° C., and obtains steel for martensitic knives that has a hardness of at least 700 HV.

An object of the present invention is to provide a low thermal expansion cast steel having a high yield strength at room temperature, a high rigidity, and a low coefficient of thermal expansion. The low thermal expansion cast steel of the present invention is obtained by suitably heat treating a cast steel comprising, by mass %, C: 0 to 0.1%, Si: 0 to 0.5%, Mn: 0 to 0.5%, S: 0 to 0.05%, Ni: 29.0 to 34.0%, Co: 0 to 8%, and a balance of Fe and unavoidable impurities so that the 0.2% proof stress becomes 350 MPa or more, the Young's modulus becomes 130 GPa or more, and the average coefficient of thermal expansion at 18 to 28° C. becomes 2.0×10.sup.−6/° C. or less.

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.