hardness of the welded joints for ASTM A 537 Cl1

[engineeronetwo]

Dear sirs

hi, our project is to supply a missing prefabricated carbon steel shell plates , the grade of the material is ASTM 537 Cl1 with 19 mm thickness , all these prefabricated steel plates are inculding manholes of 24 , 36 inch falnges , of course these flanges are connected to the shell plate and its reinforcing plate through nozzels.

Due to the huge volume of welding and because of the plate thickness (19 mm) , the plates should be PWHT according to the code API 650.

we did the PWHT as following

heating speed : 50-75 C/hr
soaking temperature: 650 C
soaking time: 1 hr
cooling speed: 45-50 C
cooling in the air out of furnace: 350C

we got a deformation in the shape of the strucure , this distortion has concentrated in the area of reinforcing plates and manhole openings.

our questions are:

1- can we get the geometery of the deformed shape by heating by tourch (heating up to 650 C and for less than 15 sec)
2- does it effect the structure of the steel itself
3- does the hardness of the welding joints effected by this process
4- what is the maximum acceptable value for hardness for ASTM 537 Cl1 within the welding joints

waiting for your kind answer please

Regards

 

[metengr]

No. In general applications spot heating can be very effective in countering distortion by introducing localized residual stresses. The problem is that you would need to heat a localized region or regions well above 650 deg F to move material. Most likely, the spot heating would result in metal temperatures that would exceed the lower critical transformation temperature resulting in hard spots (well above 35 HRC scale) in the material. Your only other option is to try to use strongbacks and re-PWHT to force the material where you want it to go.