Question

•           How close to an edge can a Rockwell Test be made?

•           Discuss conversions of hardness testing values.

•           A Rockwell HRB92 is equivalent to a Brinell hardness using a 500 kg force with a 10 mm ball of?

Answer 1

Question 1 : How close to an edge can a Rockwell Test be made ?

Answer :

The minimum distance from the edge to the point where Rockwell Hardness test can be performed is : where

Diamter of the indentation.

This is done to make sure that the test that is being performed is not influeced by the work hardening of the material at the edge of the specimen.

The minimum distance between two consecutive indents is : . This is distance is given to ensure that the work hardening effect of the pervious indent doesnot effect the hardness reading of the present.

Question 2 : Discuss the conversions of hardness testing values

Answer :

The rockwell hardness number and brinell hardness number are related by the following relationship :

For Rockwell HRC , the following table can be used to convert :

Rockwell HRC	Brinell Hardness (BHN)
21-30	BHN=5.970*HRC+104.7
31-40	BHN=8.570*HRC+27.6
41-50	BHN=11.158*HRC-79.6
51-60	BHN=17.515*HRC-401

For Rockwell HRB, the following table can be used to convert :

Rockwell HRB	Brinell Hardness (BHN)
55-69	BHN=1.646*HRB+8.7
70-79	BHN=2.394*HRB-42.7
80-89	BHN=3.297*HRB-114
90-100	BHN=5.582*HRB-319

Question 3: A Rockwell HRB92 is equivalent to a Brinell hardness using a 500 kg force with a 10 mm ball of ?

Answer :

Using the above mentioned Rockwell conversion formula :

Substitute the value :

The brinell hardness number is given by the formula:

Where

Applied load in kgf
Diameter of the ball in mm
Diameter of indent in mm

Substitute the values :

Therefore the indent diameter is :