Alloy construction nitriding steel

Steels for nitriding - characteristics and specifications

Other advantages of nitriding steel are increased abrasion resistance, higher sliding properties of the hardened surface and increased fatigue resistance.

Steels for nitriding in relation to carbon steels have 2 to 4 times higher hardness and abrasion resistance after imparting properties, and consequently, increased susceptibility to brittleness. The internal structure of the products is exposed to the frequent occurrence of cracks when used inappropriately.

Nitriding steels have also been reported to have increased corrosion resistance in environments where iron chloride, seawater, liquid oils, superheated steam, air vapor, and alkaline solutions are present.

The nitriding steel typically in the softened state is first subjected to a thermal improvement process after pre-machining and cutting of long products into shorter components. Prior to nitriding, the product should be carefully cleaned of rust, grease and oil, sharp edges causing material fragility, decarbonized surface should be cleaned leaving the finished product practically ready.

Other unevenness must be leveled with chip or grinding and stressed by tempering at a temperature above the nitriding temperature. Also note that nitriding components after the process can slightly increase their volume – approx. + 0.02% for the diameter of surface.

Application and heat treatment

The nitriding process is usually carried out at temperatures of 480-570 ℃. The higher the process temperature, the faster the nitrogen atoms enter the steel surface. If the nitriding temperature is too high, there is a risk of inversely proportional decrease in product hardness. Nitriding steels usually contain aluminum – Al, Chrome – Cr, Molybdenum – Mo. There are also steel with the addition of Vanadium and Titanium. Apart from the basic grades - 38HJ, 38HMJ, 33H3MF, materials such as 40H2MF or 35HM are also nitrided.

Nitriding steels are used for components and subassemblies of motors, machines, vehicles such as camshafts, cogwheels, piston pins, crankshafts, engine cylinders, piston rods, nitriding rods and tubes, grinding spindles and milling machines, valve plates, superheated steam valves, crankshafts, diesel fuel pump components, bushings and cylinders in pneumatic machines or push rods.

Bars and forgings of steel for nitriding

Nitriding steel described above is defined by PN-72/H-84034, PN-89/H-84030.03 standards and EN-EN 10085 European Norms; we supply:

• Seamless tubes for nitriding according to PN-72/H-74250
• Rolled sheets for nitriding
• Forgings and forged bars for nitriding according to PN-91/H-94011, EN 10250
• Cold rolled tapes for nitriding according to PN-75/H-92335
• Rolled bars for nitriding according to PN-75/H-93200, PN-55/H-93216, PN-55/H-93217, PN-72/H-93201, PN-EN 10059, PN-55/H-93218, PN-72/H-93202, PN-EN 10058,
• Bars with a bright surface for nitriding PN-72/H-93208, PN-86/H-93209, PN-85/H-93210, PN-EN 10278
• Drawn wire for nitriding PN-72/H-93208, PN-85/H-93210, PN-EN 10278