ASTM A-312/A-312M or ASME SA-312/SA-312M specification covers seamless, straight-seam welded, and heavily cold worked welded austenitic stainless steel pipe intended for high-temperature and general corrosive service, the featured grades are TP304, TP309, TP310, TP316, TP321, TP347, and TP348.

This topic to all inspector or supplier, fabricator who may need to support on reviewing material test certificate, inspection. I thinks anybody may be raised some question like

  • How to check and review MTC with an actual material?
  • What the specifications are applied to MTC and evaluate “ACCEPT” or “REJECT”?

Pipe inspection and review its MTC meet type 3.1 are a minimum of Manufacturer, heat number, specification and its grades, Manufacture/ Delivery condition, Dimensions, Weight, Mechanical properties, Chemical analysis, Heat treatment, Hydrotest or non-destructive test.


A mill or process manufacturer must correctly state in the MTC including company, work site and additional review must be included the approval’s vendor list (if any).

  • Mill manufacturer who made raw material like round, shape, etc.
  • Process manufacture who formed a product from raw material like pipe, fitting, H-shape, etc.

>> Product markings: company’s name or company’s logo are required.

Heat number

Also called heat number, ladder number (L), cast number declared in the MTC. The trace number is traceability to all the test results such as chemical analysis results, mechanical test results, NDE test results, etc. The marking code also accept in the MTC by process manufacturer which they assigned another making code under company quality manual control.

>>> Product markings: heat number or cast number are required.

Specifications and grades

A specification of material, in MTC shall be sated year of edition.

>> Product markings: specifications number and material grade. (multi-grades may be marked on the same product, dual grades may be acceptable).

Manufacture/ Delivery condition

Method of manufacture to form a production.

Example, hot finish or cold finish, seamless or welded.

Abbreviation marking and product marking:




Welded (100%RT or 100%UT)

Please note that, if grade WX or WU must require to supply the NDE reports


Including of diameter, thickness.

Tolerance of wall thickness measurement shall not less than 15% of nominal thickness and not exceed 20% or nominal wall thickness, refer to ASME B36.19.

>>> Product markings are required, ex. NPS 8” 20S


A mass per unit length, if specified in purchase order the marking for pipe larger than NPS 4 shall include the weight.

Mechanical properties

Tensile strength, yield strength and percentage of elongation its value refer to material specification. If PQR qualification should be noted and order material with dual grade for stainless steel qualification of TP304/304L, TP316/316L.

>>> Product marking is not required

Chemical analysis

Some main contents should be remarkable of %C, %Cr, %Ni, %Mo. Some MTC stated heat analysis (H) and/or product analysis (P). Tolerance refer to ASTM A999.

In some case of order, material require to re-verify by Positive Material Inspection (PMI), you should note that PMI with or without carbon (C) content requirement? because it is effected your cost, PMI with carbon (C) content is higher cost than without carbon (C) content.

>>> Product marking is not required

Heat treatment

All stainless steel pipes shall be furnished in the heat treatment condition. After hot or cold working to size, then steel heated to ~1100°C. Solution annealing is rapidly cooled by quenching into water to prevent any carbides or other phases forming.

>>> Product marking: is not required

Hydrotest or non-destructive test

Each pipe shall be subjected to the nondestructive electric test or the hydrostatic test.

>>> Product marking: hydrotest valve or NDE, both.


As specified in the purchase order such as PMI test, complied with NACE MR0175, Intergranular grain.

Stated and certified by mill signature

Manufacturer statement in certificate that the product has been manufactured accordance to the specification and purchase order, etc. and endorsed by Quality department.

Nguyen Duy Bien

Enjoy learning and researching, reading book. Knowledge welding inspection painting inspection.

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