The production process of steel smelting provides for the determination of its hardness, which is carried out in the conditions of factory laboratories. As a rule, hardness is determined in three ways: according to Brinell (GOST 9012-59), according to Vickers (GOST 2999-75) and according to Rockwell (GOST 9013-59). In order for the measurement accuracy to be reliable, it is necessary to periodically check the instruments that are used in this process. For this, there are Exemplary test blocks MTP -2 for the above methods, corresponding to GOST 9031. You can order exemplary test blocks, order here .
Brinell hardness test.
A steel ball is pressed into the sample under the action of a press. Moreover, the load must act vertically and for a certain time. Then the diameter of the print is measured. The designation of this test - HB - is a fraction, in the numerator of which is the load F or P, and in the numerator is the area of the indentation A or F. The ball can change its shape under force, therefore this method is suitable for metals with a hardness not exceeding 450 HB. Test conditions: ball D = 10 mm, P = 29430 N (3000 kgf) and force action time from 10 to 15 sec.
Vickers test.
Here a regular pyramid, of the correct shape, made of diamond is pressed into the sample. The angle is 136 degrees. Hardness in this case is the result of dividing the effort P by the area of the imprint from the pyramid. This method is suitable for determining the hardness of cemented and nitrided metals, as well as thin sheets. When determining hardness up to 450 HB, this method has the same meanings as the first method. Vickers hardness is indicated by the letters HV. The load is applied within 294 N for 10 - 15 seconds.
Rockwell metal test.
The tip is pressed with a diamond (use the A or Ce scale) or a ball (B scale). In this case, the preliminary effort is applied first, and then the main one. A measure the residual indentation (e) of the tip into the sample after the main load is no longer active. The diameter of the ball is 1.588 mm and the angle of the diamond part is 120 degrees. The hardness value is taken as the difference between the greatest penetration into the sample and the residual depth (e). Taking into account the fact that after the removal of the main force (F or P), the action of the preload Fo or Po remains. If especially hard samples are tested, then use the instrument scale A: 70-85 units. If the steel is heat-treated, the Se scale: 20-67 units. Soft metals and alloys - B scale: 25-100 units.
