Hardness Variations as Affected by Bar Diameter of AISI 4140 Steel

Hardness of the widely used structural steel is of vital importance since it may help in the determination of many mechanical properties of a material under loading situations. In order to obtain reliable information for design, properties homogeneity should be validated. In the current study the hardness variation over the different diameters of the same AISI 4140 bar is investigated. Measurements were taken on the two faces of the stock at equally spaced eight sectors and fifteen layers. Statistical and graphical analysis are performed to asses the distribution of hardness measurements over the specified area. Hardness measurements showed some degree of dispersion with about ± 10% of its nominal value provided by manufacturer. Hardness value is found to have a slight decrease trend as the diameter is reduced. However, an opposite behavior is noticed regarding the sequence of the sector indicating a nonuniform distribution over the same area either on the same face or considering the corresponding sector on the other face (cross section) of the same material bar.

Authors:

• Hamad K. Al-Khalid
• Ayman M. Alaskari
• Samy E. Oraby

Keywords:

• Hardness; Hardness variation; AISI 4140 steel; Bardiameter; Statistical Analysis.

References:

[1] D.V. Doane, "Hardenability Concepts with Application to Steels,"
Proceedings of the 108th Annual Meeting "AIME", pp. 351-379, 1979.
[2] J. Petrik , V. Miklos and V. Spetuch, "The dependence of brass hardness
measurement system on time," Metrology and Measurement Systems,
vol. XIV, no. 4, 2007.
[3] J. Petrik , V. Miklos, V. Spetuch and T. Tomps, "The influence of ball
material on the brinell hardness," Metrology and Measurement Systems,
vol. XV, no. 3, 2008.