Websler hardness testing method originated in the United States, in the 1980s with the introduction of aluminum profile production line into China. According to the principle of wechsler, the indenter of hard steel of a certain shape is pressed into the sample surface under the action of standard spring test force. The indenter depth of the indenter is used to determine the hardness of the material, and the indenter depth of 0.01mm is defined as a wechsler hardness unit.The wechsler hardness unit is called HW.
Merriam-webster hardness tester is a small portable instrument. It is small in size, light in weight, and can be operated with one hand. It can quickly, conveniently and nondestructively test the hardness of materials. It does not need sampling and requires little operation skill. It is very suitable for rapid hardness testing of materials on production site.
The disadvantages of the websler hardness tester are its poor sensitivity and narrow range, with a full range of only 20 scales. The full range is only 20 scales, so a typical instrument can only test one or two metallic materials.
2. Calibration method of websler hardness tester
Full scale correction
Do not place the sample in the opening of the durometer, and hold the handle to the bottom. As shown in figure 1, use a small screwdriver to adjust the full scale adjustment screw so that the pointer points to the scale 20. If the value indicated by the pointer is too small, adjust the adjusting screw clockwise; If the value indicated by the pointer is too large, adjust the adjusting screw counterclockwise. If you cannot adjust the adjusting screw to make the pointer point to full scale 20, you should replace the presser in time.
Load spring correction
Take out the hardness block with known hardness, and use the instrument to measure the hardness of the known hardness block. If the overtolerance is found, the instrument shall conduct load spring correction. The steps are as follows:
Unscrew the support screw, remove the lower handle from the frame, and remove the gauge head from the syringe. The syringe remains in the frame. A slotted adjusting nut can be seen in the cylinder. As shown in FIG. 2, turn the adjusting nut with the special wrench provided with the instrument. If the hardness test block reading is small, the adjusting nut should be rotated counterclockwise, and vice versa. The readout will vary by 2 ~ 3 ticks per 1/4 turn of the adjusting nut. After adjustment, the instrument should be reinstalled for hardness test.
Repeat until full scale and hardness block readings meet the requirements. Do not turn the adjusting screw except for normal adjustment. Adjustment screws shall not be used to correct the reading of standard hardness blocks.