The object of hardness testing tin plate is to determine the Temper (hardness) designation of the material. This is a classification system where the temper designation indicates the appropriate use for your tin plate. Tin plate has different and specific characteristics at each designation. The higher the temper designation, the harder the material.

You can test tin plate in either the Rockwell 15-T scale (R15T) or in the Rockwell 30-T scale (R30T) and you will always use a diamond spot anvil. The diamond spot anvil is used to avoid the “anvil effect” which is when the result of the test is affected by the steel anvil because the thinness of the material being tested did not support the major load pressure. In other words, the hardness of the anvil was tested rather than the material. The Diamond Spot Anvil is too hard to yield to the major load and, therefore, will not influence the test results. The selection of scale is determined by the thickness (or weight) of the material to be tested. The thickness of the tin plate is designated as a weight. Tests in R15T are made on plate which is less than 75 lbs. per base box. Tests in the R30T are made on plate which is over 75 lbs. per base box.

Since the standard used by the U.S. Tin Can Industry is the R30T scale, all R15T test results must be converted to R30T. For conversion and determination of Temper Designations with related characteristics, we offer the following chart:

Temper Tin Plate
Designation R30T R15T Characteristic

   T-1        52 maximum      78.5 maximum        soft for drawing

   T-2        50 to 56        77 to 80        moderate drawing
                                Where some stiffness 
                                is required

   T-3        54 to 60        79 to 81.5      shallow drawing

   T-4        58 to 64        81 to 85        general purpose
                                Where increased 
                                stiffness is required

   T-5        62 to 68        82.5 to 85.5        stiff, rephosphorized 
                                Steel used for 
                                Hardness to resist 
                                Buckling

   T-6        67 to 73        85 to 88        rephosphorized steel
                                for great stiffness

The formula for Rockwell hardness is as follows:

HR = N – (d / D)

HR = Rockwell hardness value N = total load applied to the indenter d = depth of penetration of the indenter D = diameter of the indenter

Where HR is the Rockwell hardness value, N is the load applied (in kgf), d is the depth of the indentation (in mm), and D is the diameter of the ball or the width of the diamond cone (in mm). The Rockwell hardness test uses different scales based on the load applied and the type of indenter used. The most common scales are the A, B, C, D, E, F, G, and H scales, each with a different combination of load and indenter. The Rockwell hardness test is widely used to measure the hardness of materials, including metals, plastics, and ceramics.

To apply the formula for Rockwell hardness, you will need to have the following information:

• The load applied (in kgf)
• The depth of the indentation (in mm)
• The diameter of the ball or the width of the diamond cone (in mm)

Once you have this information, you can use the following steps to calculate the Rockwell hardness value:

1. Determine the Rockwell scale: The Rockwell scale is determined by the load applied and the type of indenter used. For example, the Rockwell C scale uses a 150 kgf load and a diamond cone indenter.
2. Measure the depth of the indentation: Use a microscope or other measuring device to measure the depth of the indentation made by the indenter.
3. Calculate the Rockwell hardness value: Use the following formula to calculate the Rockwell hardness value:HR = N – (d / D)where HR is the Rockwell hardness value, N is the load applied (in kgf), d is the depth of the indentation (in mm), and D is the diameter of the ball or the width of the diamond cone (in mm).
4. Interpret the results: The Rockwell hardness value can be compared to a standard chart to determine the hardness of the material being tested.

It is important to note that the Rockwell hardness test should be performed by a qualified technician using properly calibrated equipment. The test results may be affected by factors such as the surface finish of the material and the accuracy of the measuring equipment.