Rockwell Hardness Test

If acceptablility is what the Customer is prepared to pay for, then ask the Customer instead of wasting time on CR4.

any possibility of 22 HRC as per NACE MR 0175...

HRC70 is harder than the hardest knife steel.I suspect your equipment or your measuring technique requires calibration.

Sorry welderman i was mistaken, it is 60-70 HRB.

i want to know acceptable HRB/HRC scale for the weld region.

You have to provide more info. to analyse your query.The information you provided is related to a type of fusion welding

1.What is your MOC (Material of Construction)?

2.Is there any material standards or codes of construction applicable for your material?

3.Is there any additional requirement in compliance with other standards such as NACE?

4.Is there any additional requirements set by your client/customer?

we produce ERW(Electric resistance weld) pipes and tubes,MOC as low carbon steel,we follow ASTM A 53 G-A/BS 1387 standards for manufacturing.

we dint have any customer requirement about the hardness values.

just as a QC i want to know allowable/acceptable rockwell hardness value for the weld zone.

Good ,your customer has no specific requirement on weld metal and HAZ (Heat Affected Zone) hardness value.Then why are you worrying??

ASTM A 53- Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless.

Type F-Furnace-butt welded, continuous welded Grade A

Type E-Electric-resistance welded, Grades A and B

Type S-Seamless, Grades A and B.

A 530/A 530M Specification for General Requirements for Specialized Carbon and Alloy Steel Pipe

Did you check ASTM A 53 & ASTM A 530 thoroughly ?? To find the answer for your query, we have to find the modern correlation between weld cracking and hardness value

I hope you read the above mentioned standards thoroughly and couldn't find any hardness requirement.That means it is a typical customer requirement based on service requirement and pipe metallurgy.However, there are some experimental data which showed the cracking and hardness correlation.Generally Hardness above 350 VHN (Equivalent to 36HRC) in ferritic steel weld is considered as susceptible to HAC(Hydrogen assisted cracking).The following link will give an excellent literature on hardness and weld cracking in galvanising environment.Read the pages from 38 to 50 carefully.

http://www.aisc.org/uploadedFiles/Research/Research_Reports/Kinstler%20-%20Cracks%20During%20Galvanizing.pdf