GB/T 5242-2017Inspection rules and test methods of cemented carbide products (English PDF)

3.1 Inspection items

3.1.1 Chemical composition

The inspection items of chemical composition include main metal content, total carbon and oxygen content.

3.1.2 Physical and mechanical properties

The inspection items of physical and mechanical properties mainly include density, Rockwell hardness (or Vickers hardness) and transverse rupture strength (bending strength), and where necessary, such items as coercivity (magnetization), cobalt magnetization (or magnetic saturation), cutting property, drilling property, impact toughness, thermal diffusivity, elastic modulus and drop test (or hammering test) may also be inspected.

3.1.3 Metallographic structure

The inspection items of metallographic structure mainly include porosity, uncombined carbon and microstructure of the alloy.

3.1.4 Dimension

The dimension inspection items include geometric dimension and its tolerance, positional tolerance and geometric tolerance.

3.1.5 Appearance quality

The appearance quality inspection mainly checks whether the surface of the product is subjected to delamination, cracking, poor compacting, peeling, bubbling, bending, edge defect, arris defect, burr, sticking, trace, pitting, hole plugging, pollution, oxidation, carburization, decarbonization, undersintering, overburning and other defects.

3.2 Batching rules

Cemented carbide products shall be submitted for inspection in batches, and the specific batching rules shall be consistent with the requirements of relevant standards for cemented carbide products.

3.3 Sampling rules and test methods

Each batch of cemented carbide products shall be sampled and tested in accordance with those specified in Table 1.

Table 1 Sampling rules and test methods of cemented carbide products

No. Inspection item Sampling rules Test method

1 Chemical composition Randomly take one sample from each batch of products for inspection GB/T 4324.25, GB/T 5124, GB/T 20255 and GB/T 26050

2 Density Randomly take at least two samples from each batch of products GB/T 3850

3 Rockwell hardness (or Vickers hardness) Randomly take at least two samples from each batch of products GB/T 3849 (or GB/T 7997)

4 Transverse rupture strength (bending strength) Prepare at least five specimens for each batch of products GB/T 3851

5 Coercivity (magnetization) Randomly take at least two samples from each batch of products GB/T 3848

6 Cobalt magnetization (or magnetic saturation) Randomly take at least two samples from each batch of products GB/T 23369

7 Cutting property Randomly take at least two samples from each batch of products Determined by the Supplier and the Purchaser through negotiation

8 Drilling property Randomly take at least three samples from each batch of products Determined by the Supplier and the Purchaser through negotiation

9 Impact toughness Prepare at least five specimens for each batch of products GB/T 1817

10 Thermal diffusivity Prepare at least three specimens for each batch of products GB/T 11108

11 Elastic modulus Prepare at least three specimens for each batch of products GB/T 5166

12 Drop test (or hammering test) For each batch of products, bar products with a length of no less than 150mm shall be subjected to drop or hammering test one by one, among which, those with a diameter of no less than 2mm shall be subjected to drop test, and those with a diameter less than 2mm shall be subjected to hammering test. Annex A

13 Metallographic structure Randomly take at least two samples from each batch of products GB/T 3489 and GB/T 3488

14 Dimension It shall meet the requirements of corresponding standards for cemented carbide products Inspect by using measuring tools with appropriate precision

15 Appearance quality It shall meet the requirements of corresponding standards for cemented carbide products By visual inspection. Where necessary, it shall be amplified for inspection

Note 1: For the purpose of analysis and testing, the chemical composition may be tested by using the mixture in the same batch.

Note 2: For large products with a unit weight greater than 300g, appropriately sized standard test pieces which are sintered in the same furnace may be prepared for the inspection on physical and mechanical properties and metallographic structure.