A practical RFQ method for distinguishing seamless and welded Alloy 625 tube, fixing geometry, condition, testing and document requirements before comparing offers.
Two offers can both say “Alloy 625 tube” and still describe different products. One may be cold-worked seamless pipe or tube under ASTM B444; another may be welded boiler, heat-exchanger or condenser tube under ASTM B704. The manufacturing route, product specification and intended service are purchasing inputs—not details to infer after the quotation arrives.
This guide gives buyers a structured RFQ review. It does not select a design code, establish corrosion suitability or replace the project specification. The responsible engineering party must approve those decisions.
Write what will be built: straight heat-exchanger tubes, U-tubes, instrument tubing or process pipe. Then state whether the approved design requires seamless or permits welded construction. Do not use “pipe” and “tube” interchangeably. The order should identify the product form and governing product specification explicitly.
ASTM’s published scope for B444 covers cold-worked seamless pipe and tube including UNS N06625. ASTM B704 instead covers welded UNS N06625 and other listed nickel-alloy boiler, heat-exchanger and condenser tubes. A matching UNS number therefore does not make the two routes the same ordered product.
| RFQ field | Record this | Why it matters |
|---|---|---|
| Identity | UNS N06625 plus the approved product specification and edition | Separates grade identity from product-form requirements |
| Construction | Seamless or welded; do not write “either” unless both are technically approved | Prevents an unreviewed manufacturing-route substitution |
| Geometry | Outside diameter, minimum or nominal wall basis, length, end condition, straightness and dimensional tolerances | Makes offers comparable and usable by the fabricator |
| Condition | Required grade/heat-treated condition stated in the applicable document and any subsequent fabrication | Avoids comparing properties from different conditions |
| Inspection | Required tests, examination method, acceptance basis, sampling and any witness/hold points | Stops a generic “tested” statement from replacing the project scope |
| Documents | Material report, heat/lot traceability, test records and approved deviations | Defines evidence before shipment rather than after a document gap appears |
Is the alloy correct? Verify the ordered UNS designation and the heat/lot identity in the agreed documents. Is the product route correct? Confirm seamless or welded against the purchase line and specification. Is the finished tube acceptable? Review dimensions, condition, examinations and records against the order. Passing one question does not automatically answer the other two.
For welded tube, ask the supplier to identify the governing welded-tube specification and the examination records required by the order. For seamless tube, identify its seamless product specification and the applicable general requirements. Do not invent an extra test by copying another project; specify only requirements approved for this equipment.
“OD × wall” looks precise, but the wall may be described as nominal, minimum or subject to a particular tolerance system. State the intended basis and units. If a tubesheet, bending operation or finished internal flow area controls the design, provide the drawing or the critical finished dimensions. The supplier should identify any assumed tolerance rather than silently pricing a different basis.
Illustrative review: Offer A quotes seamless tube to the requested product specification but assumes random lengths. Offer B quotes fixed-length welded tube and includes a different inspection scope. Their unit prices cannot be compared fairly until length yield, construction route, inspection and document scope are aligned.
If the requested route, size or condition is unavailable, require the alternative to be listed as a deviation. The proposal should identify what changes, which document applies, and which technical party must approve it. A commercial acknowledgement should not quietly convert seamless to welded tube or replace the specified product standard.
For international purchasing, keep the original grade and standard designation in the RFQ. Do not treat a national grade, EN number or trade name as equivalent solely because a comparison table places them on the same row. Equivalence requires a project-specific review of composition limits, condition, properties, product form and acceptance rules.
Example to complete for the project: “Heat-exchanger tube, UNS N06625, [seamless/welded], to [product specification and edition], [condition]. OD [value and tolerance], wall [minimum/nominal basis and tolerance], length [fixed/range and tolerance], ends [requirement]. Supply examination and test records required by [order clauses], with heat/lot traceability. List every exception or alternative separately for written approval before manufacture.”
Use the Alloy 625 technical data page, chemical-processing industry brief and procurement guide as planning aids. For a quotation, submit the drawing, tube geometry, quantity, specification and approved construction route through Get a Quote.
Use the edition required by your project. Source links were checked when preparing this guide.