Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Durehete Hardness in Q+T Condition — Brinell, Vickers, Rockwell C
Hardness in the quenched-and-tempered condition is the production-floor proxy for tensile strength. EN 10269 acceptance specifies Brinell HBW indentation; Vickers HV30 and Rockwell HRC correlations follow the standard conversion tables.
Brinell Hardness Range
| Grade | Q+T condition | Brinell HBW | Tempering temperature window |
|---|---|---|---|
| Durehete 1055 (T41) | Standard Q+T | 250 to 320 HBW | 660 to 730°C / minimum 2 hours |
| Durehete 950 (T31) | Standard Q+T | 240 to 300 HBW | 650 to 720°C / minimum 2 hours |
| Durehete 900 (T22) | Standard Q+T | 230 to 280 HBW | 640 to 710°C / minimum 2 hours |
Vickers and Rockwell C Conversions
| Brinell HBW | Vickers HV30 | Rockwell C HRC |
|---|---|---|
| 230 | 240 | 22 |
| 250 | 262 | 25 |
| 270 | 284 | 28 |
| 290 | 305 | 30 |
| 310 | 327 | 33 |
| 320 | 337 | 34 |
Conversions are approximate; ISO 18265 governs the formal lookup for Cr-Mo-V steels.
Hardness vs Tempering Temperature
Hardness drops approximately 8 to 12 HBW for every 25°C increase in tempering temperature within the EN 10269 window. The tempering temperature is the production lever that targets a hardness in the middle of the acceptance band; mill heat-treatment records the chosen temperature on the EN 10204 type 3.1 inspection certificate.
Test Method
10-mm ball, 3000 kgf load, 10-15 second dwell. Three indentations per bar; average reported. Surface preparation removes any decarburised layer before measurement.
Frequently Asked Questions
What hardness should I expect on Durehete 1055 bolting in Q+T condition?
250 to 320 HBW with the tempering temperature targeting the middle of the band; 280 HBW is a typical mill aim.
How do I convert Brinell to Rockwell C for Durehete grades?
Use the ISO 18265 conversion table for Cr-Mo-V steels. For example: 280 HBW corresponds to approximately 295 HV30 and 29 HRC.
Is Vickers acceptable for EN 10269 acceptance?
EN 10269 specifies Brinell as the primary acceptance method. Vickers HV30 is acceptable as a correlated check on small components such as washers and bolt heads.
Where on the bolt is hardness measured?
On the head bearing face after machining and after the final Q+T cycle. Three indentations are taken; the average is reported on the inspection certificate.
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