Reference / Steel grades
Steel and Aluminium Grade Cross Reference
Weldment drawings cross borders and grade designations do not. This is the rough map between ASTM and EN designations for the materials that actually turn up on weldments, plus what each one does to the job after you have chosen it.
Read this before using the table
These are role equivalents, not substitutes. Two grades in the same row fill the same job in their own standard. They do not have identical chemistry, identical mechanical minimums or identical impact requirements, and a drawing that calls for one is not automatically satisfied by the other. Swapping a grade is an engineering decision with a signature on it, not a purchasing convenience.
The map
| ASTM / North America | EN / Europe | Role | Strength, relative | What it changes for the shop |
|---|---|---|---|---|
| A36 | S235JR | Mild structural plate | Lowest of the structural grades | Forgiving. No preheat on normal sections. Loose as-rolled flatness, so leave machining stock. |
| A572 Gr 50 | S355J2 | Higher strength structural plate | Roughly 50 per cent above mild steel | Same processes with tighter heat control on thick sections. The J2 suffix carries a low temperature impact requirement. |
| A514 | S690QL | Quenched and tempered, weight critical | Roughly three times mild steel | Preheat and interpass control mandatory, matched low hydrogen consumables, heat input limited both ways. Stress relief can affect the temper. |
| A588 | S355J0WP | Weathering steel | Similar to A572 Gr 50 | Matching weathering consumables needed or the weld corrodes differently from the plate and shows. |
| A240 304L | 1.4307 | Austenitic stainless | Lower than structural steel, work hardens | Moves about one and a half times as much as carbon steel. Back purge closed sections, then pickle and passivate. |
| A240 316L | 1.4404 | Austenitic stainless, chloride resistant | Similar to 304L | As 304L. Chosen where chlorides or process chemistry rule out 304L. |
| B209 6061-T6 | EN AW-6061 | Heat treatable aluminium | Strong as plate, much weaker beside a weld | The heat affected zone loses a large part of its strength and does not recover without re-treatment. Design to the reduced allowables. |
| B209 5083 | EN AW-5083 | Non heat treatable aluminium | Lower than 6061-T6 as plate, better across a weld | Loses proportionally less at the joint, which is why welded structures often specify it over 6061. |
Grade suffixes carry real requirements. The J2 in S355J2 is a low temperature impact test, the L in 316L is a carbon limit that protects the heat affected zone, and the T6 in 6061-T6 is a temper that welding partly destroys. Carry the full designation onto the drawing, not just the number.
The mistake this table exists to prevent
Strength and stiffness are not the same property, and only one of them changes when you move up a grade.
Strength driven part
The part fails by yielding or breaking. Lifting structures, booms, load bearing members.
- Going to a higher grade
- Lets you use thinner plate. Saves weight, weld metal, machining and freight.
- Watch
- Preheat, interpass control and consumable cost all rise with the grade.
Stiffness driven part
The part fails by deflecting too much. Machine bases, gantries, anything holding accuracy under load.
- Going to a higher grade
- Buys you nothing. All structural steels have essentially the same elastic modulus, about 200 GPa.
- What works instead
- Section depth and geometry. Thinner high strength plate deflects more, not less.
Wear driven part
The part fails by abrasion. Chutes, liners, buckets, crusher structures.
- What to specify
- Abrasion resistant plate as a wear face on a mild steel structure, not for the whole part.
- Watch
- Plate maker heat input and preheat limits. Exceed them and the hardness at the joint is gone.
The longer version of this argument, with the cost consequences, is in choosing the steel for a machined weldment. Material specific behaviour is covered in stainless weldments and aluminium weldments and the heat affected zone.
Grade chosen. Now who makes it?
Not every shop is qualified to weld every grade. Send the drawing and we will match it with shops whose procedures cover it. Reply within 24 business hours.