YXYSteel information
Steel Plate Welding — GMAW, SMAW & SAW
Wear-resistant plate welds well when the heat is planned: carbon-equivalent matched consumables, preheat sized to thickness, heat input capped, interpass measured with a contact probe.
Why wear plate is difficult to weld
The alloy that makes the plate resist abrasion also makes the heat-affected zone harden. Three things follow: the zone can crack if it cools too fast, it can soften if it is held too hot, and the joint is usually stronger than it needs to be — which is exactly what you do not want next to a hard plate.
| Grade | CEQ (max) |
|---|---|
| NM360 | 0.56 |
| NM400 | 0.65 |
| NM450 | 0.68 |
| NM500 | 0.75 |
Above CEQ 0.60 the preheat and the interpass are no longer optional.
Preparing the joint
- Groove 30–50°, machined or gouged then ground — a burned groove with a hard rim is where cracks start.
- Clean 50 mm either side: scale, rust, paint and moisture all feed hydrogen into the weld.
- Dry the consumables: 300–350 °C for 2 hours for basic-coated electrodes; keep them in a holding oven, not on the bench.
- Check the fit-up before the first arc — root gap, root face and alignment decide the rest of the pass sequence.
Preheat
Preheat removes the fast quench that cracks the heat-affected zone. Heat the whole joint area, not just the groove, and measure it 75 mm from the weld, not at the arc.
| Grade | <10 mm | 10–40 mm | >40 mm |
|---|---|---|---|
| NM360 | room temp. | 20–75 °C | 75–200 °C |
| NM400 | room temp. | 50–100 °C | 100–200 °C |
| NM450 | room temp. | 75–125 °C | 125–200 °C |
| NM500 | 50 °C | 75–150 °C | 150–180 °C |
Choosing consumables
Match the parent metal’s strength only where the joint has to carry load; elsewhere a lower-strength, tougher filler gives the heat-affected zone somewhere to relieve itself.
| Grade | GMAW / SAW wire | SMAW electrode |
|---|---|---|
| NM360 | ER69-G-3 · ER50-6 · ER50-3 | E7015-X · E7016-X · E5016 |
| NM400 | ER69-G-3 · ER50-6 · ER50-3 | E7015-X · E7016-X · E5016 |
| NM450 | ER69-G-3 · ER50-6 · ER50-3 | E7015-X · E7016-X · E5016 |
| NM500 | ER69-G-3 · ER50-6 · ER50-3 | E7015-X · E7016-X · E5016 |
Welding methods
GMAW is the default: 80% Ar / 20% CO₂, 15–25 L/min, 1.2 mm wire. It covers root, fill and cover on plate from 6 mm up and keeps the heat input predictable.
SMAW suits site work and repairs where the gas line does not reach; basic-coated electrodes only, straight from the holding oven.
SAW is used for long straight seams on thicker plate, where the higher deposition rate pays for the handling.
| Pass | Current (A) | Voltage (V) |
|---|---|---|
| Root | 150–240 | 22–26 |
| Fill | 260–300 | 28–31 |
| Cover | 260–300 | 28–31 |
Heat input, interpass and cooling
- Heat input ≤15 kJ/cm below 10 mm, ≤25 kJ/cm at 10 mm and above.
- Interpass never below the minimum preheat, never above 200 °C — measured with a contact probe, not estimated.
- Slow cooling: cover or blanket sections over 50 mm so the joint cools in air, not in a draught.
- No post-weld heat treatment, and no flame straightening — both take the hardness out of the plate you paid for.
Questions we get before the PO
Can you weld NM500 without cracking?
Yes, with 50 °C minimum preheat below 10 mm, 150–180 °C above 40 mm, capped heat input and no flame straightening afterwards.
Do you supply WPS and PQR?
Welding procedure and qualification documents travel with the order where the project requires them; tell us the standard at enquiry stage.
Can the weld prep be cut and beveled by you?
Yes — the groove is milled after cutting, so the bevel matches the WPS instead of the torch.
Can you weld after priming?
No. Primer has to be removed 50 mm either side of the joint, or the plate is welded before priming. We plan the sequence at order stage.
Need a plate solution?
Cut, machined, welded and surface-prepared under one roof in Rizhao.