Bronze is an alloy of copper with 12-15% tin along with other metals like zinc, nickel, manganese, and aluminum and metalloids Bronze was one of the most widely used metals during the Bronze Age.
Bronze has different alloys which are classified into different types according to numerous criteria.
These are Silicone bronze, Bismuth bronze, Plastic Bronze, Commercial Bronze, Classic Bronze, Mild Bronze, Alpha Bronze, etc. Bronze has various uses since prehistoric time.
It is most widely used for coins, ship and boat fittings, propellers, bearings, sculptures, springs, automobiles, etc. As it has numerous uses, its quality should be checked before using it.
The hardness of bronze can be investigated by many methods. The hardness of a metal is the ability of itself to resist indentation. Different methods used to assess the hardness of bronze are-
Rockwell Hardness Test
The Rockwell test was invented by Stanley.P.Rockwell and Hugh M Rockwell from the USA. Bronzes hardness can be determined using the Rockwell method.
Many variants of this test are present. But the general principle is the same. In this method, the surface of the metal to be tested is pressed upon with an indenter under a determined force and the indentation is measured.
But in this case, the indenter that is used is a ball of steel or diamond in contrast to the carbide ball used for Brinell Hardness Testing of metals.
The Rockwell scale is expressed as a random dimensionless number where the last alphabet describes respective Rockwell scale, example HRA, HRB, HRC, HRD, HRE, etc. There are different types of Rockwell Hardness Tester on the basis of the Rockwell scale.
Knoop Hardness Test
It is a type of micro indentation test in which indentations are made with a force that does not exceed 1kgf. The principle of this test is similar to the hardness test used for metals by other methods.
It uses a diamond indenter which under a specified force makes an indentation on the polished surface of the sample.
Knoop Hardness Number (KHN) is a ratio that can be calculated dividing the amount of force applied by the unrecovered projected area. Its value ranges from 100 to 1000.
It has various advantages like it’s precision level is more, it can be performed at the microscopic level, quick output with low cost, it can also be performed to check whether the sample under investigation has the desirable property for the required use.