Processes commonly used for austenitic stainless steels and carbon steels can be used for duplex stainless steel cutting, but some adjustments to the parameters are necessary to accommodate mechanical and thermal properties.
Duplex stainless steel is more difficult to saw than carbon steel due to its high strength, high work hardening rate and lack of inclusions that act as chip breakers. High-powered machines, powerful saw blade straightening systems, rough sawtooth saw blades, slow-to-medium speed cutting speeds, heavy feeds, and adequate coolant flow (preferably a combination of lubrication and cooling) The emulsifier allows the saw blade to transfer the coolant to the workpiece, etc., to give the best results. The cutting speed and feed rate should be similar to those of 316 austenitic stainless steel.
The duplex stainless steel is cut to the same equipment as the 304 and 316 stainless steels, and generally requires no special adjustment. However, due to the high shear strength of duplex stainless steel, it is necessary to increase the shear force or reduce the shear thickness.
For hot rolled and cold rolled sheets, the shear strength of stainless steel is about 58% of the tensile strength. According to the actual shear strength ratio, duplex stainless steel behaves like a thicker 316 stainless steel. Therefore, in a particular shear, the maximum thickness of 2304 and 2205 duplex stainless steels can be sheared to about 75% of the thickness of 304 and 316 stainless steel, while the maximum thickness that super duplex stainless steel can be sheared is ordinary austenitic 65% of the body stainless steel.
Conventional steel coil slitters can be used to cut duplex stainless steel coils and strips. The duplex stainless steel coil is fed from the uncoiler and passed through a circular slitting blade of the lower tool holder on the slit line, and the take-up reel rewinds the sheared steel coil. The position of the slitting blade can be adjusted according to the desired width of the coil product. Since the strength of duplex stainless steel is higher than that of austenitic stainless steel, the wear of the slitting tool and the stability of the edge are difficult to control. Maintaining a good longitudinal edge quality of a duplex stainless steel coil requires the use of tool steel or carbide inserts.
Punching can be seen as a difficult form of shearing. High strength, fast work hardening and tear resistance make duplex stainless steel relatively difficult to punch and wear the tool. A better entry point and guiding principle is to treat duplex stainless steel as a double-thickness austenitic stainless steel. Punching of high alloyed duplex stainless steels with higher nitrogen content is more difficult.
5. Plasma and laser cutting
Duplex stainless steels are typically processed using the same plasma cutting and laser cutting equipment as austenitic stainless steel. The slightly higher thermal conductivity and low sulphur content of duplex stainless steel may have a slight effect on the optimum parameters, but satisfactory results can be obtained without special adjustments. The heat affected zone (HAZ) of the plasma cutting process is generally very narrow, about 0.25 mm (0.010 inch), because the cutting is a single pass, fast operation, and the sheet cools quickly. The machining of the weld bevel and the melting of the metal near the base metal during the welding process remove the heat affected zone of the plasma cut. s difference.