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ASTM Induced Confusion (low alloy steel grades in A234 and others)

ASTM Induced Confusion (low alloy steel grades in A234 and others)

ASTM Induced Confusion (low alloy steel grades in A234 and others)

(OP)
I am having trouble comprehending the essential differences between Class 1 and Class 2 of WP11, as well as between Class 1 and Class 3 of WP22 (and where is Class 2?) Of course it has to do with heat treatment, but the wording in ASTM A234 could not possibly be more obscure. Based on the tensile properties I can make educated guesses, but you know where assuming gets you.
Help please!

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: ASTM Induced Confusion (low alloy steel grades in A234 and others)

ironic metallurgist
The strength levels, aka Class, can be achieved either through HT or chemical composition. There can be overlap (dual certification) between the strength Classes. If you have more issues you would be better served to contact the ASTM committee and relay your concerns directly.

RE: ASTM Induced Confusion (low alloy steel grades in A234 and others)

(OP)
Thanks metengr,
Given the significant differences between strength levels, I would have expected two distinctly different heat treatment paths; e.g., normalizing vs. Q&T.
Although in my (admittedly limited) encounters with grade 22 I have only ever noticed 60ksi minimum UTS specified.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: ASTM Induced Confusion (low alloy steel grades in A234 and others)

Yes, I agree. However, on occasion I have run across WP22, Class 3 from added spices from the mill which provided a boost in tensile properties.

RE: ASTM Induced Confusion (low alloy steel grades in A234 and others)

(OP)
I'm allergic to spices if you know what I mean. Instability and all that.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: ASTM Induced Confusion (low alloy steel grades in A234 and others)

A234/SA234 have been there for ages, well understood by design/metallurgical engineers. You need to refer a few ASTM specifications to understand the whole concept.
Refer A960/SA960, Clause 7. Heat Treatment
7.1 Fittings requiring heat treatment shall be treated as specified in the individual product specification using the following procedures:
7.1.1 Full Annealing
7.1.2 Solution Annealing
7.1.3 Isothermal Annealing
7.1.4 Normalizing
7.1.5 Tempering and Post-Weld Heat Treatment
The above clause & HT requirements are specified in Clause 7 of A/SA234

Based on the heat treatment various Tensile Strengths are achievable. Table -2 of A/SA234 classifies/categorizes the fittings as per tensile strengths.
CL1 Fittings- Tensile Strength Range- 60–85 KSI
CL2 Fittings- Tensile Strength Range- 70–95 KSI
Cl3 Fittings- Tensile Strength Range- 75–100 KSI

A/SA234, Table-1 clearly specifies the chemical analysis for each class.

Note: As stated previously by Metengr & as narrated above tensile ranges could be overlapping, resulting in duel certification of the fittings. This helps the designer to choose the right grade with correct HT and strength, with minimal brain teasing.
Often instead of specifying the highest strength for a selected class, it's better to switch or provide the option of selecting the next class, as the tensile strengths are overlapping

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

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