How to Read a Mill Test Certificate for Steel Plate Coil and Pipe

What the Certificate Is For

A mill test certificate is not a marketing document. It is the record that connects the steel on your truck to the grade, the standard and the tests that were actually performed on that material. Without it a grade written on a packing list is a claim rather than a fact.

Tianyu Metal supplies a mill test certificate with carbon steel plate and coil, alloy and mold steel, stainless sheet, wear resistant plate and round bar, and certifies welded line pipe to EN 10204. The company also holds ISO9001, BV, SGS and RoHS certification, which is separate from the certificate that travels with a specific batch.

• Mill test certificate issued against the ordered grade
• Certificate travels with the batch not with the company
• ISO9001 BV SGS and RoHS are company level certifications
• Ask for the mill test certificate at the quotation stage so the format is agreed early

Check the Certificate Type Under EN 10204

EN 10204 defines the types of inspection document issued for metallic products, and the type is the first thing to look at because it tells you who validated the results. ERW welded pipe and LSAW welded pipe from Tianyu Metal are certified to EN 10204/3.1Ba, and galvanized welded round steel pipe is certified to EN 10204/3.1.

Where your project specification names a certificate type, confirm it on the inquiry rather than after production. Changing the document type after rolling is far harder than agreeing it before the order is placed.

• ERW welded steel pipe certificate EN 10204/3.1Ba
• LSAW welded steel pipe certificate EN 10204/3.1Ba
• Galvanized welded round steel pipe certificate EN 10204/3.1
• SSAW pipe certified to EN10217 EN10219 API 5L PSL1 or PSL2 and API 5CT
• Agree the certificate type before production starts

Match the Grade and the Standard to Your Order

The second pass is the simplest and catches most problems. Read the grade and the governing standard on the certificate and compare them word for word with the purchase order. A grade family is not a grade: S355JRH and S355J2H sit in the same family and behave differently in a cold climate.

Steel pipe is written against standards such as API 5L, ASTM A106, ASTM A53, EN10217, EN10219, DIN 2458, JIS G3452, BS1387 and GB/T9711, and carbon steel coil against EN10025, ASTM A573, ASTM A283, GB/T 700-2006, GB/T711-2008, JIS G3101, JIS G3131 and JIS G3016. Confirm which one your certificate is issued against.

• Compare the grade on the certificate to the grade on the purchase order character by character
• Confirm the governing standard and its revision reference
• Line pipe grades run L175 L210 L245 L320 through to L555 and API 5L X42 to X65
• Casing grades run H40 J55 K55 N80 L80 13Cr C90 T95 and P110
• Structural coil grades include Q195 Q215 Q235B Q345B S235JR S355JR SS400 and SS490

Read the Chemical Analysis Section

Chemical component analysis is listed as a standard test on welded pipe and it is the section that determines whether the material will behave as the grade says under welding and heat treatment. Read it against the composition limits of the named standard, not against a general expectation.

For stainless material the chemistry section is the grade. Stainless steel contains a minimum of approximately 11 percent chromium, which is what prevents the iron from rusting and gives it heat resistant properties, and carbon runs from 0.03 percent to greater than 1.00 percent depending on the type, alongside nitrogen, aluminum, silicon, sulfur, titanium, nickel, copper, selenium, niobium and molybdenum.

• Chemical component analysis performed on ERW LSAW and SSAW pipe
• Stainless steel contains a minimum of approximately 11 percent chromium
• Stainless carbon content ranges from 0.03 percent to greater than 1.00 percent
• Compare every element against the limits of the named standard
• Chemistry drives weldability so check it before writing the welding procedure

Read the Mechanical Test Section

Mechanical properties on a pipe certificate cover ultimate tensile strength, yield strength and elongation. These three figures are what a structural calculation actually relies on, so they are the numbers to transcribe into your own records.

Where the grade name encodes a strength value, check that the certificate supports it. S690 high strength structural steel is defined by a minimum yield strength of 690 MPa, with the S denoting structural and the 690 indicating yield strength. On heat treated bar the equivalent check is hardness: 1045 C45 S45C 1.1191 CK45 round bar is normally delivered at 18 to 25HRc, and after water quenching at 820 to 870 degrees Celsius its hardness is quoted at 201 to 269HB.

• Ultimate tensile strength yield strength and elongation reported on pipe
• S690 is defined by a minimum yield strength of 690 MPa
• 1045 C45 CK45 round bar delivery hardness 18 to 25HRc
• Hardness after water quenching at 820 to 870 degrees Celsius quoted at 201 to 269HB
• Ballistic plate is quoted at 500 to 600 HBW with 1250 MPa yield and 1600 MPa tensile strength

Read the Technical and Nondestructive Tests

The technical property tests prove that the product survives forming and pressure rather than just meeting a composition. On ERW pipe these cover the flattening test, bending test, blow test and impact test, plus exterior size inspection and a hydrostatic test.

LSAW pipe adds an X-ray test to that list. SSAW pipe is tested by bending, Charpy V impact, hydrostatic and X-ray tests together with a metallographic test. On a pressure line, the hydrostatic and X-ray results are the two entries an inspector will look for first.

• Flattening test bending test blow test and impact test on ERW pipe
• Hydrostatic test on ERW LSAW and SSAW pipe
• X-ray test on LSAW and SSAW pipe
• Charpy V impact test and metallographic test on SSAW pipe
• Exterior size inspection recorded alongside the mechanical results

Check Dimensions Coating and Marking Last

The last pass is dimensional. Exterior size inspection appears on the pipe certificate, and the figures there should match the ordered size band. ERW pipe runs 21.3mm to 660.4mm outside diameter with a 1.5 to 22.2mm wall, LSAW runs 355.6mm to 1820mm with a 5.0 to 50mm wall, and SSAW runs 219.1mm to 3048mm with a 4mm to 30mm wall.

Then confirm the surface condition on the certificate matches what you ordered, because coating is part of the specification. Options include fusion bond epoxy, coal tar epoxy, 3PE, varnish, bitumen and black oil coating on line pipe, and black painted, galvanized or natural on seamless pipe.

• Confirm outside diameter wall thickness and length against the size band you ordered
• Seamless wall is stated by schedule SCH5S through SCH160 and XS from 1.65mm to 80mm
• Confirm the coating named on the certificate is the coating ordered
• Check the marking on the material matches the certificate before unloading
• File the certificate with the maintenance or fabrication record for the part

What to Do if the Certificate Does Not Match

Raise a mismatch before the material is cut. Once a plate is in pieces or a pipe is welded into a line, the commercial options narrow quickly and so do the technical ones.

The fastest route is to send the certificate and the purchase order side by side to your contact and ask for the discrepancy to be explained in writing. Dinah can be reached at [email protected] and Jass at [email protected], or Chat on WhatsApp for a same day answer.

• Stop cutting or welding until the discrepancy is resolved
• Compare certificate grade standard chemistry and mechanical results against the order
• Ask for the mill test certificate to be reissued where a clerical error is confirmed
• Email Us at [email protected] or [email protected] with both documents attached
• Chat on WhatsApp on +86 199 6352 2611 or +86 153 4544 9731