Choose welding steel against the requirements of the finished joint and the fabrication route before ordering stock. A familiar grade name and an attractive tensile result leave important questions open: the delivery condition, the other member being joined, and the evidence that the joint can meet its service requirements.
This guide covers material selection and procurement qualification. Use the strength-grade guide for the design strength basis and the stainless welding guide for process-specific practice. No universal preheat temperature, heat input or filler designation is prescribed here.
1. Define the component after welding
Give the supplier and fabricator the drawing revision, product form, thickness range, joint arrangement and service environment. State which requirements apply to the supplied steel and which must be demonstrated on the completed fabrication. Include the required inspection and acceptance documents in the enquiry.
Welding changes local properties. SSAB separates weld metal, heat-affected zone and parent steel; its recommendations are product-specific. Obtain evidence for the completed joint separately from the parent-metal certificate.
Ask the responsible engineer to identify the governing acceptance requirements. Depending on the application, these may address joint strength, toughness, fatigue-sensitive details, corrosion performance or dimensional fit. Record the relevant test locations and conditions when specified. Do not turn a material’s Charpy test temperature into an approved service temperature for the entire component.
2. Identify the actual material offered
Request the complete standard and grade, producer, product form, thickness, delivery condition and surface treatment. Keep these fields together when comparing offers. The HSLA reference explains why a broad family name leaves the product specification incomplete.
List any subsequent forming, heat treatment, galvanizing or coating in the proposed manufacturing sequence. Ask the supplier which guidance covers that sequence and which operations require additional review. A recommendation for another thickness, delivery condition or producer is a lead for enquiry, not documented coverage of this offer.
For existing or unidentified stock, keep identification unresolved until the required evidence is obtained. Appearance, a supplier nickname or an untraceable certificate does not establish a heat or grade. Agree how offcuts and transferred stock will retain identification before they enter production.
3. Read carbon equivalent with its method attached
For relevant carbon and low-alloy steels, request the applicable carbon-equivalent method and supporting composition. TWI’s comparison explains that CEIIW, CET and Pcm use different formulations and applicability. Avoid ranking unmatched values.
On the quotation review sheet, record the method, chemistry basis, applicable document and whether the result is a maximum requirement or a reported heat value. If the information is absent, ask for it; do not fill missing alloy entries with zero or select whichever equation gives the lowest result.
Keep chemistry in context. TWI’s hydrogen-cracking guidance identifies the interaction of hydrogen, susceptible microstructure and tensile stress. Thus a low carbon-equivalent figure alone cannot approve a joint. Have the welding coordinator assess the offered material within the proposed procedure and actual joint conditions.
4. Check that the workshop can qualify the offer
Before buying production quantity, send the material dossier to the fabrication team. Ask for a clear response: covered by an applicable procedure, requires additional qualification, or unsuitable for the proposed route. A general claim that the shop “welds this grade” leaves the scope unresolved.
| Review item | Evidence to request | Decision to record |
|---|---|---|
| Material identity | Exact grade, condition and thickness | Offer matches the material dossier |
| Procedure scope | Applicable welding procedure specification and supporting basis | Coverage confirmed or additional qualification required |
| Required joint properties | Relevant qualification or test records | Requirements covered and gaps assigned |
| Inspection and release | Agreed plan, criteria and responsible persons | Stock and fabrication releases remain distinct |
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For stainless steels, use family- and grade-specific advice: TWI’s stainless overview identifies different welding responses across the families. For coated steel, resolve substrate identity, weld-zone preparation, exposure controls and restoration of protection with the galvanized welding guide . Do not authorize coating removal or hot work through the purchase description alone.
5. Compare a proposed substitute without losing the evidence
Consider a fictional fabricated bracket. Offer A matches the documented material and delivery condition used for the approved route. Offer B meets the requested strength class, but has a different delivery condition and only a typical chemistry sheet. B’s shorter lead time does not establish interchangeability.
Mark what is confirmed and what remains open. Obtain B’s exact product documents; have the responsible engineer review service requirements and the welding coordinator review procedure coverage. Agree any necessary qualification, inspection and change approval before releasing the substitute. Do not assume that one successful demonstration weld covers all joint details or production thicknesses.
If the original route needs changing, compare the total consequence: qualification effort, consumables, production controls, inspection and delivery time. Record the approved combination of material and process. Keep rejected or unconfirmed alternatives out of the released order.
6. Put the decision into the purchase and release record
Use the steel specification guide to carry the accepted material identity into the order. Attach a bounded list of welding-related requirements:
- Full product designation, delivery condition, thickness and surface/coating condition.
- Required chemistry and weldability evidence, with calculation method and document revision.
- The fabrication route and the person responsible for confirming its coverage.
- Required material certificates and traceability through cutting and assembly.
- Any agreed qualification, inspection or supplementary testing and acceptance responsibility.
- A change-notification and approval route for substitutions in material, producer or condition.
Separate the purchasing release from permission to weld. Resolve material-document discrepancies before the affected stock is released; let the authorized fabrication controls govern production. Preserve the accepted dossier so a later repeat order can be checked against the same baseline instead of relying on the previous order’s short description.