Steel Hardness and Strength Conversion
Metal hardness is a measure of its resistance to deformation when stressed. In metals, hardness is usually related to strength but not always. For example, steels can vary in strength, but all steels are relatively hard when compared to softer materials such as plastics or rubber. Strength and hardness in metals are related but not always the same. A material can be hard but not very strong, while one can be strong but not particularly hard. Steel is a common example of this. There are different grades of steel depending on the hardness and strength. In order to properly compare steel, it is important to understand the differences between the terms.
Hardness is typically measured using the Rockwell scale, which uses a diamond of specified size and shape to indent a specimen and then measuring the indentation hardness. Hardness is usually expressed as an HRC number, which indicates the Rockwell hardness. The equivalent Vickers Hardness number can also be used. Strength, on the other hand, is usually measured using tensile tests, which measure the force necessary to break, stretch, or deform a material. By comparing the values from these two tests, it is possible to make a good approximation of the relationship between the hardness and the strength of a steel.
The relationship between hardness and strength is not always linear and can vary depending on the steel grade. For example, mild steels such as 1018, 1020, and 1045 all have relatively low HRC values, yet they may have different tensile strengths. On the other hand, some higher alloy steels such as 4140 and 4340 have higher HRC values, but their tensile strengths are considerably greater than those of the mild steels. As such, there is no single or direct conversion that can be applied to every steel grade.
In general, higher hardness does increase the strength of a steel, but this increase usually decreases at HRC values above 50. However, for high strength steels a higher HRC value often indicates a higher strength level. In addition, the difference in strength between two steels of equal hardness can be quite large depending on the alloy composition and other factors.
When comparing two steels from different grades, a hardness and strength conversion chart can be useful. Alternatively, the hardness and strength of each steel can be determined by performing tensile strength tests and Rockwell hardness tests. It is important to note, however, that these conversions are not exact and should be used as a general guide only.
In order to accurately compare steel hardness and strength, it is important to understand what hardness and strength actually mean and how they relate to one another. Hardness is used to measure the resistance of a material to deformation and is typically expressed as an HRC or Vickers Hardness number while strength is used to measure the force necessary to deform or break a material, and is usually measured using tensile tests. In general, higher hardness does increase the strength of a steel, but this increase usually decreases at HRC values above 50. In addition, since the relationship between hardness and strength is not always linear, it is important to use a hardness and strength conversion chart or to perform tests to accurately compare two steels from different grades.
