Hardness is the measurement used in investment casting foundry to check the properties of cast metals and their suitability for different applications. For cast steels and metals, hardness is the property that shows a material’s ability for its intended use.
The values ascribed are due to a complex combination of deformation and elastic behavior. Hardness is the property that shows a materials ability to resist permanent deformation when it is under load. For the acceptable investment castings, the tested casting hardness value must be within the given range, relevant hardness value will be listed on the MTR and submit to our customer for approval.
There are several different tests exist for measuring the hardness of cast steels and cast metals, Brinell Hardness Testing, Rockwell Hardness Testing and Vickers Hardness Testing.
Brinell Hardness Testing- which uses specified large loads by pressing a hardened steel or carbide sphere of fixed diameter into a casting for a set time. The indentation that is created in the metal is measured for its diameter. The Brinell hardness test uses method ASTM E10-Standard Test Method for Brinell Hardness of Metallic Materials. The brinell hardness value of steel castings will be shown in HB.
Rockwell Hardness Testing-The equipment applies a preliminary test force to the casting using a diamond or ball indenter. The purpose of this stage is to break through the surface of the metal and reduce the effect of surface finish on the final result. The operator measures a baseline indentation depth at this point. After holding the preload for a set time, a major load is then applied. Again, the force is held for a pre-set time, before reducing it to the preload force again. The Rockwell hardness number is based on the difference between the baseline and final depth measurements. Rockwell test has two stages. The Rockwell hardness test uses method ASTM E18-Standard Test Methods for Rockwell Hardness of Metallic Materials. Rockwell hardness value of steel castings will be shown in HRC.
Vickers Hardness Testing-which uses a microscope to measure the depression caused on a polished surface by a diamond indenter with a load of kilograms.
There are many factors affect the grading of cast steel, such as chemical composition, mechanical properties and heat treatment processes, all of them play a role in the certification of each cast product against the applicable standard or ITP. Usually, steel castings are heat treated to manipulate their properties. For any higher hardness, could be achieved by heat treatment, such as quenching and tempering, induction hardening, carburizing treatment and so on.
With the development of the testing equipment has made it easier for our steel foundry to estimate the hardness of our castings based on one simple test. Hardness testing is a kind of non-destructive, means it can be carried out on finished products without causing big damage. Another advantage of hardness testing helps our steel foundry have a second check the heat treatment processes. The results show whether the microstructure of the material has changed as expected. Hardness testing is a critical component of quality control for investment casting foundries.
At Ningbo Investment Casting Co., Ltd., our steel foundry will complete a full set of certification tests prior to shipping castings to our customers.