Technical knowledge
Heat numbers and mill test certificates: reading the paperwork properly
What a heat number identifies, what a mill test certificate to EN 10204 3.1 must contain, how to spot a weak certificate, and how to keep traceability intact from melt to installed asset.
What a heat actually is
A heat, or cast, is the batch of metal produced from one melting operation. Every component made from that melt shares the same heat number and the same chemical analysis. Mechanical properties, however, depend on the product form and the heat treatment applied afterwards, which is why a certificate must quote both the heat analysis and the results for the delivered condition.
What the certificate must contain
| Item | Why it matters |
|---|---|
| Heat number | The traceability link |
| Specification and UNS or grade | Confirms what was ordered |
| Heat analysis, actual values | Not ranges; actual measured chemistry |
| Mechanical test results | Yield, tensile, elongation, hardness where specified |
| Heat treatment description | Confirms the condition supplied |
| Dimensions and quantity | Confirms what was shipped |
| NDT results | Confirms the agreed examination scope |
| Signature or authorised stamp | Confirms validity |
Warning signs on a certificate
- Ranges instead of actual values. A certificate that quotes specification limits rather than measured results provides no evidence.
- No heat treatment description. The condition is often the most consequential variable in an alloy order.
- Missing heat number. Without it, nothing can be traced.
- No link to the component. The number on the certificate must match the number marked on the part.
- Certificate scope broader than the item. Check that the certificate actually covers the delivered size and form.
When independent verification is needed
Where the owner, EPC or regulator requires independent verification, inspection, sampling and laboratory testing by SGS can be arranged, and the resulting third party test report is issued with the shipment. This complements rather than replaces the mill certificate, and it is normally required for critical service, for large projects and for public sector procurement.
Questions about this topic
What is the difference between a heat number and a batch number?
A heat number identifies the melt, which is the source of the chemistry. A batch or lot number may refer to a production or heat treatment batch, which can include more than one heat. Only the heat number gives chemical traceability.
Is EN 10204 3.1 enough for critical service?
It is the standard certificate for most projects. Where independent verification is required by the owner or regulator, third party inspection and testing is added and the resulting test report accompanies the shipment.
What should I do if the marking is lost during fabrication?
Transfer the heat number to a tag or to the fabrication record before the marking is removed. Cutting or machining a component without recording its heat number breaks the traceability chain permanently.
Questions about our products
What products does Hangbo Alloy supply?
Four product families, all available in nickel-based alloys, titanium, duplex and special stainless steel: flanges, butt weld pipe fittings, elbows, and seamless tube and pipe. Flanges cover weld neck, long weld neck, slip-on, blind, socket weld, threaded and lap joint patterns. Fittings and elbows cover concentric and eccentric reducers, equal and reducing tees, caps, stub ends, and 45°, 90° and 180° returns in both long and short radius, plus 3D and 5D bends for piggable lines. Seamless tube and pipe is supplied cold drawn or hot finished from 6 mm to 630 mm outside diameter.
Which alloy grades are available for these products?
More than 90 grades are published in our grade library. The most requested are Inconel 625, 718, 600 and X-750, Hastelloy C-276, C-22 and B-2, Monel 400 and K-500, Incoloy 800H, 825 and 925, duplex 2205 and super duplex 2507, 316L, 904L and 254SMO stainless steel, and titanium Grade 2 and Grade 5. Nickel-based grades can also be supplied with VIM plus ESR double melting where cleanliness or fatigue life is critical.
What sizes, wall thicknesses and pressure classes can you supply?
Flanges run from NPS ½ to NPS 24 to ASME B16.5 and from NPS 26 to NPS 60 to ASME B16.47 Series A or B, in pressure classes 150 through 2500. Butt weld fittings and elbows run from NPS ½ to NPS 48 (DN 15 to DN 1200) in wall thickness Schedule 5S through XXS. Seamless tube and pipe covers 6 mm to 630 mm outside diameter, in random lengths of about 5 to 7 metres or fixed lengths up to 12 metres. Non-standard and intermediate sizes are quoted on request.
Which material and dimensional standards do you work to?
Forged flanges to ASTM B564, B381 and A182 with dimensions to ASME B16.5 and ASME B16.47. Butt weld fittings and elbows to ASTM B366 and A403 with dimensions to ASME B16.9 and MSS SP-43. Seamless tube and pipe to ASTM B444, B423, B622, B163, B167, B861, A312, A213 and A790. Marking follows MSS SP-25 and the applicable product standard. If your project is governed by EN, DIN, JIS or a company specification, send the document and we will confirm equivalence before quoting.
Is there a minimum order quantity?
There is no minimum for standard sizes and grades held in stock, and prototypes, spares and small trial batches are accepted. Made-to-order melts and special forgings carry a minimum weight that depends on the alloy and the route, typically from about 500 kg for special grades.
What inspection and certification is issued with the goods?
Every shipment carries an EN 10204 3.1 mill test certificate quoting the actual chemical and mechanical results for the specific heat lot, together with dimensional records and heat treatment data where applicable. Testing is carried out in house by optical emission spectrometry, tensile, impact and hardness testing, plus ultrasonic and eddy current examination, with hydrostatic pressure and intergranular corrosion testing to ASTM G28 or A262 Practice E where the specification requires it. Third party inspection by SGS or another recognised agency can be arranged, and their report is issued alongside the shipment.
What are typical lead times?
Standard stock items ship within days. Common production grades such as Inconel 625 or duplex 2205 are typically a few weeks. Special chemistries, larger forgings and items that require third party inspection take longer and are quoted individually against the requirement.
How are the products packed for export?
Flanges and fittings receive a rust preventive coating, are individually wrapped and are packed in plywood cases secured with steel banding. Tube ends are capped and bundles are strapped. Packing lists quote heat numbers so every case can be cross-checked against the mill certificate on arrival. We quote EXW, FOB, CFR, CIF and DAP, and mixed-alloy orders can be consolidated into one shipment with a single documentation package.
How do I request a quotation or a sample?
Send the grade or UNS number, the dimensions including schedule or wall thickness, the governing material and dimensional standards, quantity, any heat treatment or NDT scope and the certificate type you need; a drawing is ideal for special flanges and fittings. Email demi@nickel-alloy.com or message us on WhatsApp +86 15618279078 and we normally issue a formal quotation within 24 hours on working days. Samples and previous test reports can be arranged before the first order.
Talk to an engineer
Share your duty conditions and we will shortlist candidate alloys within one working day.