The design and manufacture of metallic components require that designers specify the hardness of the metal parts. However, designers often have difficulty deciding what hardness scale to use in their specifications. Most designers try to convert their hardness testing scales to more suitable ones like Rockwell hardness B and C scales. This article compares two types of Rockwell hardness to help you find the most ideal of the two for your hardness testing and conversion needs.
I. What is Rockwell Hardness B?
Rockwell hardness testing method is widely accepted in many industries with different scales. The Rockwell hardness B scale has more accuracy when testing soft metals like brass, aluminum, and mild steel. Its use often involves an indenter with a known shape and load to cause a depression that is measured to ascertain the hardness of the material. Further, it uses a steel ball hardened to have a more indentation effect on the material. The ball’s weight is usually 100kg, and its hardness value is identified with HRB.
Related Article: Rockwell B Scale
II. What is Rockwell Hardness C?
With an indenter with a diamond tip and a cone shape, the Rockwell hardness C uses a weight of 150kg to cause a measurable depression on the material surface, which gives the material hardness. However, Rockwell hardness C is more suitable for harder materials and, as such, is often applicable to testing materials that include hard steel. HRC is used to measure the hardness value for Rockwell scale C, and it helps to identify it when converting it to other hardness scales.
III. Which is Harder Rockwell C or B?
When deciding the hardness testing scale to use between Rockwell hardness C and B, it is often best to confirm the material’s hardness or softness and thickness. This information helps to determine which is more suitable for testing the material. However, the Rockwell hardness scale C is harder than B and unsuitable for thin and soft materials like aluminum and brass. It is often used for harder and very thick materials like hardened steel.
IV. What is the Difference between Rockwell B and C?
Some differences make the Rockwell B and C hardness scale suitable for specific uses. Some of these differences are obvious, and others are not. The indenter types are one of the apparent differences as Rockwell hardness B uses a hardened ball made of hardened steel while the Rockwell C scale uses a cone-shaped indenter with a diamond tip. Also, the weights of the indenters used are pretty different as type B indenter ball weighs 100kg while type C weighs 150kg. Furthermore, they are used for different levels and thicknesses of material samples.
V. Can you Convert HRB to HRC?
Converting hardness Rockwell B (HRB) to hardness Rockwell C (HRC) is a usual practice for many designers when specifying the hardness value of a material. This conversion is possible using charts and tables calculated using formulas to get approximate but acceptable values that can be interchanged for the different Rockwell hardness testing scales.
VI. Rockwell B to C Hardness Conversion Chart
Rockwell Hardness Conversion Table
Rockwell B (HRB)
Rockwell C (HRC)
In conclusion, identifying the best hardness testing scale to use will depend on the level of hardness testing of the material. While the Rockwell hardness testing scale is prevalent, it is best to consider the material thickness and softness to select the most suitable scale between Rockwell B (HRB) and Rockwell C (HRC). This will ensure the accuracy of the result of the hardness testing value.
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