Acidur 4122 QT750

Automotive industry, Pump shafts, Food and Beverage industry, Mechanical engineering, Cutting Tools, Building industry

Good - As a result of its higher chromium content, 17 %, 1.4122 is more corrosion resistant than 1.4006 and other 13 % chromium stainless steels. Good corrosion resistance is displayed in moderately corrosive media/environments with low chloride ion concentrations. Although the addition of molybdenum increases the resistance of this steel to chloride containing environments, it is not suited for use in sea water applications unless it is provided with cathodic protection. Optimal corrosion resistance is attained when the surface is finely ground or polished. PRE = 18.47 – 20.46

With Care - The machinability of this grade of stainless steel is directly related to its hardness and as such the optimal machining parameters vary considerably. Once the hardness is known, the machining parameters can be estimated since 1.4122 machines similar to carbon steels of the same hardness. Although it must be realised that the machining parameters will vary depending on the structure/hardness of the steel.

1.4122 can be soft annealed by holding at a temperature in the range 750 °C to 850 °C followed by slow cooling in air or in a furnace. 1.4122 can be hardened by holding at a temperature between 980 °C – 1060°C followed by cooling in oil or polymer. The tempering temperature is dependent on the desired strength. The heat treated condition usually specified is the QT750 condition and is obtained by tempering in the temperature range 650 °C to 750 °C.

Quenched and tempered QT 750

With Care - This grade of steel is not usually welded, but if absolutely no alternative exists, then the workpiece is to be pre-heated to a temperature within the range 300 °C – 400 °C prior to welding. Since a large amount of untempered martensite will form in the heat affected zone, a subsequent tempering treatment will be required. Since this tempering treatment will over temper the already tempered martensite in the rest of the work piece, it would be preferable if the entire component were hardened and tempered, as described above. Once again, the time lapse between welding and heat treatment must be as short as possible to reduce the possibility of cracking. When the application of a filler metal is required, then Novonit® 4576 can be used.