Testing Tin Plate with an Ames Portable Superficial Tester
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