HARDOX is the commercial name of the wear-resistant (abrasion-resistant) steel series produced by SSAB. Its high hardness (typically 370–640 HBW) makes it the material of choice for excavator buckets, conveyor bodies and wear plate applications on various machines.
Welding HARDOX steels requires special procedures due to their high hardness values. Incorrect parameter selection can lead to cold cracking, loss of hardness or HAZ embrittlement.
HARDOX Series Comparison Table
| Grade | Hardness (HBW) | Min. Yield (MPa) | CEV (typical, t=20mm) | Typical Application |
|---|---|---|---|---|
| HARDOX 400 | 370–430 | 1000 | ≤ 0.47 | Conveyor liners, general wear |
| HARDOX 450 | 425–475 | 1250 | ≤ 0.54 | Bucket teeth, crusher jaw plate |
| HARDOX 500 | 470–530 | 1400 | ≤ 0.61 | Rock crusher, bucket bottom plate |
| HARDOX 600 | 570–640 | 1650 | ≤ 0.77 | Extreme wear; special WPS mandatory |
Welding Challenges and Precautions
The main challenges when welding HARDOX steels:
- Cold Cracking Risk: The high CEV value makes the weld zone susceptible to hydrogen-induced cold cracking. H5 or H4 class low-hydrogen filler material is mandatory.
- HAZ Hardness Loss: Excessive heat input reduces hardness in the heat-affected zone (HAZ) and decreases wear resistance.
- Interpass Temperature Control: Not exceeding 200°C maximum is critical; otherwise the tempering effect permanently reduces hardness.
Note for HARDOX 600: This grade falls outside the scope of standard MIG/MAG WPS. A special procedure must be developed with a separate WPQR and manufacturer technical support.
CEV Calculation and Preheat
Preheat temperature is calculated according to EN ISO 1011-2 Method B. HARDOX 450 at 20 mm thickness typically requires 75–100°C preheat; for HARDOX 500 this value can reach 100–150°C. Parameters used in the calculation: carbon equivalent (CEV), diffusible hydrogen content (HD), combined thickness and heat input. Preheat must be applied at least 75 mm from the weld line and maintained throughout welding. When ambient temperature is below +5°C, the calculated preheat value is automatically increased.
HARDOX Applications at ArmaWeld
ArmaWeld holds approved WPS documents under EN ISO 15614-1 for HARDOX 400, 450 and 500. H5 class low-hydrogen wire (MAG) and basic coated electrode (SMAW) are used as filler materials. In bucket and wear plate production, MAG welding is predominant and a controlled pass strategy is applied to fillet welds. Interpass temperature is measured with a thermocouple for every job and recorded in the weld log. This discipline has eliminated early-wear complaints in the field.
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