Three abbreviations appear on almost every steel indent in India. They are related but not the same thing.
| Term | What it is | Who issues it |
|---|---|---|
| ISI mark | Certification mark showing the product is made under a BIS licence to the Indian Standard | Bureau of Indian Standards (licence held by the producer) |
| TC — test certificate | Document recording chemistry and mechanical test results for the lot supplied | The producer |
| MTC — mill test certificate | The TC issued by the producing mill, traceable to heat / cast number | The producing mill |
"ISI & TC" on an order therefore asks for two things: ISI-marked material, and the producer's test certificate for the lot. In trade usage, TC and MTC are often used interchangeably.
What a test certificate shows
- Producer, product, standard and grade
- Heat / cast number and, for plates, plate or batch identification
- Chemical analysis (C, Mn, S, P, Si and others as required)
- Mechanical properties — yield strength, tensile strength, elongation, impact values where applicable
- Dimensions and quantity covered
Certificate types in project specifications
Project specifications often reference EN 10204 certificate types: 2.2 (test report based on non-specific inspection), 3.1 (inspection certificate on the delivered lot, validated by the producer's authorised inspector) and 3.2 (as 3.1, additionally validated by the purchaser's or a third-party inspector). State which type is required.
ISI, non-ISI and local make
Not every product on the market is ISI-marked. Some secondary-mill sections and "patra" pipes are sold without ISI certification at a lower price. For structural, pressure, fire-fighting and project work, specify ISI-marked material with TC. See ISI vs patra pipes and primary producer vs local make.
In the enquiry
Say whether ISI marking is required, whether a TC / MTC is required and which type, and whether third-party inspection applies. Material for traceable supply is sourced differently from general stock, so this belongs in the enquiry, not at dispatch.
Related: HR plates · Structural steel · How to write a steel RFQ