Martensitic stainless steels are widely used in the steam generators, oil and gas esploration, oversea petroleum platforms, pressure valves, mixer blades, cutting tools, and surgical tools and jigs.
Owing to their excellent mechanical properties. In general, these steels are used in quenched and tempered conditions.
Quenching heat treatment is carried out by cooling in oil or air followed by annealing at 980–1100 °C. Tempering is done at the interval of 200 and 700 °C .
The annealed Martensitic stainless steels have a microstructure containing spherical carbides in the ferritic matrix.
Since the material is metallurgical complex, the heat treatment must be accurately controlled in order to create a complete martensite structure without forming δ-ferrite and residual austenite.
Stainless steel 1.4021 is a martensitic machining bar with machinability improved with the addition of Sulphur. The Sulphur also lowers weldability, corrosion resistance, and formability to below that of its non-free machining equivalent Grade 410.
Stainless Steel – Martensitic – 1.4021 Bar Properties, Applications and Fabrication
Martensitic stainless steels are designed for high hardness, and other properties are compromised to an extent. Their functional operating temperature range is restricted by their loss of ductility at sub-zero temperatures, and loss of strength by over-tempering at high temperatures.
Alloy designations of 1.4021 is similar, but it may not be a direct equivalent to: 420, UNS42000, 1.4021, 1.4024, 1.4028, 1.4029, 1.4030, and 1.4034. It is supplied in the form of a bar.
Corrosion resistance is lower than the common austenitic grades. It offers resistance to fresh water, dry atmospheres, and mild alkalies and acids; however, the resistant is lower than equivalent non-free-machining grades. High Sulphur content free machining grades – such as 416 – are not suitable for chloride exposure or in marine condition.
Maximum corrosion resistance can be achieved in the hardened condition with a smooth surface finish. The steel has a fair heat resistance to scaling in intermittent service up to 760°C, and up to 675°C in continuous service. It is not recommended for use in temperatures exceeding the relevant tempering temperature.
|1.4021 Steel||EN 10088-3:2005|
|Chemical Element||% Present|
|Carbon (C)||0.16 – 0.25|
|Chromium (Cr)||12.00 – 14.00|
|Manganese (Mn)||0.0 – 1.50|
|Silicon (Si)||0.0 – 1.00|
|Phosphorous (P)||0.0 – 0.04|
|Sulphur (S)||0.0 – 0.03|
|Thermal Expansion||10.3 x10^-6 /K|
|Modulus of Elasticity||200 GPa|
|Thermal Conductivity||24.9 W/m.K|
|Electrical Resistivity||0.055 x10^-6 Ω .m|
|Bar – Up to 160mm Dia/Thickness||EN 10088-3:2005|
|Proof Stress||500 – 600 MPa|
|Tensile Strength||700 – 950 MPa|
|Elongation A||12 – 13 %|
Fabrication must be carried out by methods that allow for poor weldability, as well as for a final harden and temper heat treatment.
Cold working – It is not recommended, It is only suitable for minor deformation. Cracking will occur due to severe deformation.
Hot working – Hot working processes should be carried out after uniform heating to 2100-2250°F (1149-1232°C). Hot working below 1700°F (927°C) could result in cracking.
Machinability – Grade 420 offers very good machinability, the highest of any of the commonly available stainless steels. It is achieved best in sub-critical annealed condition.
Weldability – Grade 420 has poor weldability. It can be pre-heated to 150-320°C and post-heated at 610-760°C. Grade 420 coated welding rods can be used for high strength joints, where a post-weld hardening and tempering heat treatment can be carried out. If parts need to used in the “as welded” condition, a ductile joint can be made using Grade 309 filler rod or electrodes.
The main areas of applications include:
- Automatic screw machined parts
- Valve parts
- Pump shafts
- Motor shafts
- Bolts and nuts
- Shear blades
- Cutlery blades
- Surgical Instruments
- Washing machine parts
- Deutsche Edelstahlwerke