Which Stainless steel bolts to be used between A193 and A320 based on the temperature conditions?

[ATUL KHATRI]

Hello Experts,
I need some clarification regarding the selection of bolting material between A193 and A320 specifically for stainless steel grades i.e B8,B8C,B8T,B8M etc.
Standard specifications A193 and A320 , are for alloy-steel and stainless steel bolting materials intended to be used in high temperature and low temperature services respectively.

For alloy-steel bolts its quite evident that A320 clearly highlight the requirement of impact test for low temperature conditions whereas A193 refers A320 for the lower temperature condition. Also the minimum and maximum temperature limits are different for both, as per ASME B31.3. So no confusion in selecting the alloy bolt material specification as per temperature conditions.

But for stainless steel grades of these specifications ,for the same grade and same class (for example A193 GrB8M cl2 and A320 GrB8M cl2), the maximum and minimum temperature limits along with their material composition (As per ASME B31.3), mechanical properties (yield and tensile strength ), is identical. So on what basis (mainly the temperature limits) we can identify which material to be used ?



I am not sure that is there any specific difference of heat treatment and manufacturing process in both the specifications specifically for stainless steel grades ? I tried to find out for the individual specifications but couldn't get it .

Also if there is a limit of use of A193 at lower temperature than what is that limit ? is that below -29 deg C we should go for A320 ?

Also if there is a limit of use of A320 at higher temperature than what is that limit ? is that above 125 deg C we should go for A193 ?

I again want to highlight that my query is related to stainless steel grades not alloy grades.

Thanks in advance.

 

[metengr]

The austenitic stainless steel bolting Grades do not exhibit a ductile to brittle transition behavior, typical of low alloy steel grades. Because of the concern with elevated temperature creep and low temperature fracture behavior of alloy steel grades, there needed to be two different bolting material specifications.

Since the austenitic stainless steel bolting grades overlap in both bolting material specifications, one can use either A 193 or A 320 for low or higher temperature service. I want to caution you that for elevated temperature service cold worked austenitic stainless steel grades have their limitation to avoid softening or reduced strength, whereas, for low temperature service, the cold worked austenitic stainless steel grades can be limited for very low temperature service.

So, what this means is that the designer can select either material specification for use with austenitic stainless steel grades when design conditions permit.

 

[SnTMan]

I'd add that your Code of Construction (if any) may place limits on whether -193 or -320 may be used. See, for example, ASME Sec II, Part D, Table 3 and notice the columns for Applicability and Maximum Temperature Limits for the various Sections / Divisions.

Regards,

Mike

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