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[MW:25667] S 690 QL Heat Straightening

By Materials & Welding
Dear All,
 
Please find my quary as below regarding Heat Straightening and Hardness of S 690QL material
 
We are doing fabrication and welding of S690 QL as per EN 1090-2 and to rectify welding distortion we performed and heat straighten for S690 material at 550°C as per the following codes.
 

EN 10025-6

:

Technical delivery conditions for flat products of high yield strength structural steels in the quenched and tempered condition

CEN/TR 10347

:

Guidance for forming of structural steels in processing

 
Unfortunately out fabrication team performed Heat straightening at 700°C and we have verified Hardness and we obtained 180 HV10 to 250HV10(Lowed Hardness values), But En 1090-2

Table 10 — Permitted maximum hardness values (HV 10) specifies max 450 HV10. Since EN 1090-2 does not specifies the min Hardness, is 180 HV10 to 250HV10 are acceptable? if yes what would be the minimum acceptable Hardness value? is there any code or specification specifies the minimum Hardness values?

 

So final out put is S 690 QL material is becoming soft instead of hard.

 

Heat straightening parameters are as following

Fuel: Oxygen and Acetylene

Heating Method: Manuel

Heating Measuring Technique: Digital Thermometer   

 

Thank You,

Best Regards,

Hema santosh

 

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