Stainless Steel 316L 1.4404

This data sheet applies to stainless steel 316L / 1.4404 hot and cold-rolled sheets/plates and strip, semi-finished products, rods, rolled wire and profiles as well as seamless and welded tubes for pressure purposes.

Application

Construction encasement, doors, windows and armatures, offshore modules, cisterns and pipes for chemical tankers, production, warehousing and overland transportation of chemicals, food and beverages, pharmacy, synthetic fibre, paper and textile plants and pressure vessels. Due to the low C-content, the resistance to intergranular corrosion is also guaranteed in the welded condition.

Processing / Welding

Standard welding processes for this steel grade are:

• TIG-Welding
• MAG-Welding Solid Wire
• Arc Welding (E)
• Submerged Arc Welding (SAW)
• Laser Beam Welding

When choosing the filler metal, the corrosion stress has to be regarded, as well. The use of a higher alloyed filler metal can be necessary due to the cast structure of the weld metal. A preheating is not necessary for this steel. A heat treatment after welding is normally is normally not usual. Austenitic steels only have 30% of the thermal conductivity of non-alloyed steels. Their fusion point is lower than that of non-alloyed steel therefore austenitic steels have to be welded with lower heat input than non-alloyed steels. To avoid overheating or burn-though of thinner sheets, higher welding speed has to be applied. Copper back-up plates for faster heat rejection conductivity a greater distortion has to be expected. When welding 1.4404 all procedures, which work against this distrotion (eg. back-step sequence welding, welding alternately on opposite sides with double-V butt weld, assignment of two welders when the components are accordingly large) have to be respected notably. For produc thicknesses over 12mm the double-V butt weld has to be preferred instead of a single-V butt weld. The included angle should be 60° - 70°, when using MIG-welding about 50° are enough. An accumulation of weld seams should be avoided. Tack welds have to be afficed with relatively shorter distances from each other (significantly shorter than those of on-alloyed steels), in order to prevent strong deformation, shrinking, or flaking tak welds. the tacks shoudl be subsequently grinded or at least be free from crater cracks. 1.4404 in connection with austenitic weld metal and too high heat input the addiction to form heat cracks exists. the addiction to heat cracks can be confined, if the weld metal features a low content of ferrite (delta ferrite). Contents of ferrite up to 10% have a favourable effect and do not affect the corrosion resistance generally. The thinnest layer as possible have to be welded (stringer bead technique) because a higher cooling speed decreases the addition to hot cracks. A preferably fast cooling has to be aspired while welding as well, to avoid the vulnerability to intergranular corrosion and embrittlement. 1.4404 is very suitable for laser beam welding (weldability A in accordance with DVS bulletin 3203, part 3) Witha welding groove width smaller 0.3mm respectively 0.1mm product thickness the use of filler metals is not necessary. With larger welding grooves a similar filler metal can be used. With avoiding oxidation within the seam surface during laser beam welding by applicble backhand welding, eg. helium as inert gas, the welding seam is as corrosion resistant as the base metal. A hot crack hazard for the welding seam does not exist, when choosing an applicable process. 1.4404 is also suitable for laser beam fusion cutting with nitrogen or flame cutting with oxygen. The cut edges only have small heat affected zones and are generally free of micro cracks and thus are well formable. While choosing an applicable process the fusion cut edges can be converted directly. Especially, they can be welded without any further preparation. While processing only stainless tools like steel brushes, pnematic picks and so on are allowed, in order to not endanger the passivation. It should be neglected to mark within the welding seam zone with oleigerous bolts or temperature indicating crayons. The high corrosion resistance of this stainless steel is based on the formation of a homogeneous, compact passive layer on the surface. Annealing colours, scales, slag residues, tramp iron, spatter and such like have to be removed in order to not destroy the passive later. For cleaning the surface the processes brushing, grinding, pickling or blasting (iron-free silica sand or glas spheres) can be applied. For brushing only stainless steel brushes can be used. Pickling of the previously brushed seam area is carried out by dipping and spraying, however, often pickling pastes or solutions are used. After pickling, carefully flushin with water must be done.

Remark

In quenched condition the material can be slightly magnetizable. With increasing cold forming the magnetizability increases.

Editor

thyssenkrupp Materials (UK) Ltd
Cox’s Lane
Cradley Heath
West Midlands
B64 5QU

Important Note

Information given in this data sheet about the condition or usability of materials respectively products are no warranty for their properties, but act as a description. The information, we give on for advice, comply to the experiences of the manufacturer as well as our own. We cannot give warranty for the results of processing and application of the products.