Q355 Steel: Specify the Full Grade, Form and Delivery Condition
The official record lists GB/T 1591-2018 as current. Its inspected original text shows that a complete designation includes a yield-strength number, delivery-condition symbol and quality grade after Q. That still does not settle the tests or performance of an unspecified offer. Before comparing quotations, write the full ordered designation, product form, delivery condition and certificate requirements in one place.
- Designation
- Q355
- Family
- Low-alloy steel
Full designation
Include the exact quality suffix
Standard edition
Name the document used for acceptance
Product form
Separate grade identity from coil or plate form
Delivery evidence
Set condition, tests and certificate requirements
Write the Full Grade, Not a Short Family Name
The official record identifies GB/T 1591-2018 as current. In the inspected original text, clause 4.1 builds a complete designation from Q, the specified minimum yield-strength number, a delivery-condition symbol and a quality grade; it gives Q355ND as an example. The example explains the structure of the name, not the suitability of that exact grade for your order.
Copy the full designation from the approved engineering specification. If only Q355 is written, ask which delivery symbol, quality grade and acceptance requirements are intended before a seller chooses them. Do not infer chemistry, impact results or a foreign-grade match from the short name.
Check the Suffix Against the Ordered Tests
Use the complete clause 4.1 designation and the current standard edition on the enquiry. Clause 5.1 starts the ordering-information list with the standard number, product type, designation and dimensions. Add the project's required tests, inspection document and any further purchase conditions after checking the applicable clauses and drawing; the designation alone does not establish a numeric impact or strength acceptance table here.
A quote should repeat the approved designation and proposed test basis. If the seller proposes a different quality grade, delivery condition or standard, treat that as a separate offer for engineering approval before the purchase order changes.
Specify Product Form and Thickness Separately
Clause 1 of GB/T 1591-2018 lists plates, strips, sections and bars for general structures and engineering. State the ordered form and dimensions instead of assuming that a Q355 designation means every shape is supplied. If the drawing calls for plate but procurement requests coiled strip, resolve the form and any further processing before comparing offers. Pipe is not established by this inspected scope.
Check the applicable form, thickness and tolerance provisions for the actual request. This page gives no numerical size band; the linked Q355B coil page does not itself establish an offer for plate, section or bar.
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Record the Delivery Condition
Clause 4.1 makes the delivery-condition symbol part of the complete designation. Clause 7.1 separates chemical-composition tables by delivery category. Record the exact ordered condition, surface and edge requirements, and any processing planned after receipt; then check the applicable table and certificate entries for that condition. No chemistry values are reproduced here.
If two offers use the same short grade but different conditions, keep them on separate comparison lines. The engineer must check the proposed condition against the part's fabrication and service requirements.
Use the MTC to Close the Order Identity
Compare the mill test certificate with the purchase order: full designation, standard and edition, product form, delivery condition, test entries and heat identifier. Match the heat identifier to the delivered material. An absent or different entry should be resolved before incoming acceptance.
If the material is proposed as an alternative to a drawing specification, the certificate is evidence about the actual heat, not permission to change the design. Obtain the technical owner's written decision against the project's acceptance requirements.
Take the Approved Specification to a Coil Enquiry
When the ordered material identity and form are clear, send the full designation, size, condition, quantity, destination and intended processing in your enquiry. Use the published commercial coil page to examine the available options and request a scoped quotation. This grade reference adds no new steel form, dimension, stock or delivery promise.
Frequently Asked Questions
No. Write the full approved designation and standard edition, then add product form, delivery condition, dimensions and required certificate entries.
The engineering specification should settle the required suffix and tests before offers are compared. Treat a proposed change as a separate offer requiring technical approval.
The official record lists GB/T 1591-2018 as current. Its inspected clauses explain designation construction and initial order fields, but the applicable tables and footnotes still need review for the exact form, condition and acceptance basis.
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