Corrodur 4028 QT850 – High‑Carbon Martensitic Steel for Construction & Fasteners

Automotive industry, Decorative applications, Kitchen utensils, Electronic equipment, Mechanical engineering, Pump and Valve components, Cutlery and Blades

Good corrosion resistance in moderately corrosive environments that are free of chlorides, such as soaps, detergents and organic acids. Good resistance in oxidising atmospheres up to temperatures of about 600 °C. 1.4028 is not resistant to intergranular corrosion in the asdelivered or as-welded conditions. Optimal corrosion resistance is obtained in the hardened condition with a polished surface finish. From a corrosion point of view, 1.4028 displays the same or slightly reduced resistance to corrosion than 1.4021. This is due to the higher carbon content resulting in the removal of more chromium from solution and the development of a more highly stressed microstructure in 1.4028. PRE = 12.0 – 14.0

The machinability of this grade of stainless steel is directly related to its hardness. 1.4028 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.

1.4028 can be soft annealed by holding at a temperature in the range 745 °C to 825 °C followed by slow cooling in air. 1.4021 can be hardened by holding at a temperature between 950 °C – 1050 °C followed by cooling in air or oil. Care must be taken to ensure that the time at the hardening temperature is sufficient to take any carbides that might be present into solution. After hardening and stress relieving at 200 °C, the hardness should not exceed 48 HRC, (460 HB). The tempering temperature is dependent on the desired strength. Due to the precipitation of undesirable phases, the temperature range 400° C to 600 °C should be avoided. In most cases the QT850 condition is specified and may be obtained by tempering in the temperature range 625 °C to 675°C

It is formable at 800-1100°C

Quenched and tempered QT 850 and stress relieved before peeling

1.4028 is generally not welded, but if welding is unavoidable, then the following precautions should be taken: Pre-heating of the work piece to a temperature within the range 300 °C – 400 °C is required as well as a post weld tempering treatment to restore some of the ductility in the weld zone. Generally, Novonit® 4551 is recommended when a filler material is required. When using an inert or protective shielding gas during welding, care must be taken to avoid use of any hydrogen or nitrogen containing gases since contamination of the weld with nitrogen or hydrogen will adversely affect the mechanical properties. After welding the work piece must be cooled to below the martensite start (MS), temperature of approximately 120 °C before being tempered.