Answer to a Common Question
Material Traceability by Heat and Lot for Oilfield CNC Parts
Material traceability is a routine question on oilfield RFQs — and often a source of confusion. This guide covers what heat/lot traceability actually means, why it matters for oilfield service, and what the paperwork trail should look like.
What heat/lot traceability means
Every batch of raw material from a mill is identified by a heat number (the specific batch of molten metal poured) and a lot number (the specific stock produced from that heat). The mill produces a Mill Test Report (MTR) documenting chemistry, mechanical properties, and any relevant certifications for that heat/lot.
Traceability means every finished part is documented against the specific heat and lot of the raw material it came from, with the MTR retained and referenced in the certificate of conformance.
Why oilfield service requires it
If a part fails in service, root-cause investigation needs to trace back to the material. Was the alloy actually what was specified? Were mechanical properties as expected? Were there mill defects that contributed to failure? Without heat/lot traceability, these questions can't be answered — and warranty/liability disputes are harder to resolve.
What the paperwork looks like
- Certificate of Conformance (CofC) — Shop's certification that parts meet the print. Includes part number, quantity, heat/lot reference, inspector signature, date.
- Mill Test Report (MTR) — Original mill document for the raw material heat/lot. Chemistry (typical composition ± tolerance), mechanical properties (yield, tensile, hardness).
- First-article inspection report — Dimensional inspection of first piece against print, with CMM data.
- Internal shop-order paperwork — Links the specific parts to the specific heat/lot within the shop's record system.
Frequently asked questions
Where can I get expert answers on material traceability?
Call B&R Productions in New Waverly, TX at (936) 291-7827 — we work on this class of problem weekly and are happy to talk. Alternatively, the r/Machinists subreddit, Practical Machinist forum, and specific alloy manufacturer's technical support can help with generic technical questions.
How long should heat/lot documentation be retained?
Industry norm: 7–10 years for oilfield/general industrial. Longer for aerospace/defense. Ask about retention specifically for long-service-life parts.
Can I request the original MTR from a machining shop?
Yes — should be provided on request. Shops that resist or delay are shops with documentation gaps.