Product Specification

Welding Stainless Steel Wire: Grade, Heat Input and What Comes After

Welding wire is usually discussed as a filler question. On stainless wire it is three decisions instead: the carbon level of the wire, the heat input at the joint, and what happens to the surface after the arc stops. Get the grade right and skip the last step, and the weld can still rust before the rest of the part does.

This wire is supplied annealed at 550-750 N/mm2 or in spring temper, from 0.15 mm to 12 mm, in 304, 304L and 316L. The low-carbon L grades are the ones specified for welded assemblies, because carbon is what precipitates at the grain boundaries in the 450-850 C band.

Two limits belong in the same conversation. Heat tint left by welding is a chromium-depleted oxide that has to be removed rather than polished over, and carbon steel tooling transfers free iron onto stainless that will show as pitting within weeks of delivery.

Product Specifications

Grade Choice Comes First

Carbon level sets the weld zone

Standard 304 holds roughly 0.08% carbon. Held in the 450-850 C range during welding, that carbon combines with chromium at the grain boundaries and leaves the adjacent metal short of chromium. 304L and 316L at 0.03% max limit that precipitation, which is why they are specified where the joint stays in service.

316L where chlorides follow the weld

Welding leaves a heat-tinted surface that is less protective than the base metal. In a chloride environment that is where pitting starts. 316L with molybdenum gives the joint more margin, and the tint still has to be removed.

Ferritic grades are a separate case

430 welds, but the grain coarsens at the joint and toughness drops, and prolonged service near 475 C embrittles the grade. Where a welded part must be ferritic, the joint location and heat input need designing rather than assuming.

Heat Input and Joint Design

Short arc, fast travel

On wire sections the whole cross-section heats quickly, so the goal is to finish the joint before the surrounding metal soaks. Low amperage, short arc time and a heat sink behind the joint all reduce the width of the affected zone.

Gas coverage and the tint

Loss of shielding shows up as a straw or blue tint rather than a visible defect. Good coverage, and a trailing shield on heavier sections, keeps the oxide thin enough to passivate afterwards.

Where the joint sits relative to the bend

A weld in a bend zone is a stress riser in the least ductile part of the wire. Moving the joint outside the bend radius, or welding before the final form where possible, is cheaper than changing the grade.

What Comes After the Weld

Passivation restores the oxide layer

Passivation removes free iron from the surface and lets the chromium oxide layer re-form evenly. It is the step that most often separates a part that lasts from one that shows rust spots in the first season.

Pickling where the tint is heavy

Passivation will not remove a thick heat tint, because the depleted layer sits beneath the oxide. Pickling or a pickling paste removes it, followed by passivation to finish.

Tool contamination

Brushes, clamps and cutting tools previously used on carbon steel transfer free iron that pits in a chloride environment. Keeping stainless tooling separate is a discipline, not a purchase.

Applications

Welded mesh panels and guards

Panels and machine guards welded from 1-4 mm wire, where a clean joint and an even surface matter as much as strength.

Baskets and frames for wet service

Food and process baskets in 316L, where the weld is inside a washdown environment and cannot be recoated.

Railings, grilles and architectural infill

Visible welded assemblies where heat tint would be seen, so pickling and passivation are part of the finish specification.

Product Advantages

• Low-carbon L grades available - 304L and 316L at 0.03% max limit chromium carbide precipitation at the weld.
• One tensile basis per order - the annealed or spring temper band is fixed at order stage, so welding behaviour does not shift between coils.
• Clean surface on supply - free of embedded iron and drawing residue, so pitting starts at the weld if it starts at all.
• Grade scope stated plainly - 304 for dry and general service, 316L where chlorides follow the weld, and a warning that 430 coarsens at the joint.
• Post-weld guidance included - passivation and pickling are described as part of the process, not left as an assumption.
• Full size range - 0.15-12 mm, so mesh wire and frame wire are welded on the same documented basis.

Quality Control

Rod grade is verified by chemical or PMI check before drawing. Diameter is measured inline and at coil ends, tensile and elongation are tested per heat per ISO 6892-1, and surface is inspected for scale, die lines and iron contamination. Carbon content is confirmed on the mill test report for L grades.

Selection and Ordering Notes

1. State whether the part is welded, and whether the joint stays in service or is cosmetic.
2. Name the cleaning regime after welding: passivation, pickling, or neither.
3. Confirm the temper, since spring temper changes how the joint behaves under heat.
4. Give the joint position relative to any bend, so the heat-affected zone can be placed.
5. Provide sizes and annual volume for a tolerance and packing review.

Send the grade, diameter, welding process and post-weld requirement for technical confirmation and quotation.