Using metal Lowl hardness timing you need to know
Local hardness meter work principle
Under the prescribed conditions, press the header (diamond cone, steel ball or hard alloy ball) in two steps into the sample surface. After removing the main test force, the remnants depth H measured under the initial test force. Remnant depth H represents the level of hardness.
1 — The depth of the initial test power F0; 2 — pressure in the total test force F0+F1; 3 — removing the elastic recovery depth of the main test power F1; 4 -residual pressure depth H; 5; 5; 5; 5; 5; 5; 5; – Sample surface; 6 — Measure the benchmark surface; 7 — Press the head position
Luo’s hardness value is calculated according to the following formula:
N -constant, for A, C, D, N, T rules, n = 100; other ruler, n = 130;
H -residual indentation depth, mm;
S -constant, for Lowl Hardness, S = 0.002mm, for surface Luos hardness, s = 0.001mm. Each Robe’s hardness unit is the corresponding indentation depth, Lowl’s hardness is 0.002mm, and the surface of the surface is 0.001mm. The lighter the indentation, the higher the hardness. The Lowl Hardness Test is divided into two types, one is the common Lowl hardness test, and the other is the surface of the Robe hardness test. The Luoz hardness test adopts three types: 1200 diamond cone and 1.588mm, 3.175mm steel ball, and uses three types of test for 60kg, 100kg, and 150kg. They have nine combinations, corresponding to the nine standards of Lowl’s hardness, that is, HRA, that is, HRA , HRB, HRC, HRD, HRF, HRF, HRG, HRH, HRK. The surface of the Robe hardness test uses two types of pierced heads of 1200 diamond cone and 1.588mm steel balls. It uses 15kg, 30kg, and 45kg test forces. They have six combinations, corresponding to the six standards of the surface of the surface of the surface, namely HR15N, HR30N, HR30N , HR45N, HR15T, HR30T, HR45T.
Common problems and error analysis
1. Different surface cleanliness shows different impacts when the hardness test of the Lohto in Cangzhou. The lower the surface of the surface, the higher the hardness during the high hardness test, and the lower the hardness, the rough surface of the knife marks. The first time is cooled during quenching, or the hardness value is high. Conversely, when the quality of the quality is recovered at high temperature, the surface tissue with knife marks is transformed first, with a small ability to resist the fire, and the hardness value is low. When testing the parts below the surface of the surface of the surface, the waste sand wheel must be grinded, and then the knife is grinded smoothly, or the fine sand wheels are polished, and then wiped it clean.
2. The surface of the heat treatment parts has salt, sand, etc. When the load is added, the parts will be slippery. If there is greasy presence, the diamond head will be lubricated when the head is pressed in, reduces friction, and increases depth. These two reasons make the measured hardness low. The thin hardness value of the oxidation and vegetable layer of the part of the part is reduced, and the thickness of the thickness of the dense dense layer of the oxide is increased. For parts that want to test hardness, the oxidation skin must be removed, wiped clean, and there must be no dirt.
3. The error of the hardness test of the slope (or cone), the spherical and cylindrical parts is larger than the plane. When the head is pressed into the surface of such parts, the surroundings that are pressed into the area are smaller than the plane, and there is even a phenomenon of deviation and slippery. The smaller the curvature radius, the greater the slope, and the significant decrease in the hardness value. Vajrayana head is also easily damaged. Design a special workbench for such parts to make the workbench and head concentric.
Before testing the Lowl hardness meter, it should be inspected to ensure;
1. The hardness meter installation is correct;
2. The main axis of the head can slide in its guidance body;
3. Press the handle and install it firmly in the main axis hole;
4. The exertion and unloading of the experimental power without impact or vibration does not affect the reading;
5. The displacement of the sample or the deformation of the rack does not affect the reading. When the lock device with locking the sample locks to the parts above the rack, its lock force should exceed the total test force. The effect of the transformation of the rack can be replaced by a piercing head with a spherical head (not less than 10mm in diameter) to the main axis, and the pad is pressed on the test platform L (when the lock device is locked, the lock should be tightened by locking device. The device presses the pad block and then pressed on the test platform for inspection. Lowl’s hardness of the spindle and block material should not be less than 60 HRC. The readings of the measurement device (applied the initial test force), before and after the hardness*major test force is applied and removed, the difference between the two in the hardness meter without locking device should not exceed 1.5 Luo’s units; The difference between the hardness meter with a locking device should not exceed 0.5 Luo’s units.
1. Calibration of experimental power; for the initial test power F0 and each total test force F used, as long as possible,*should be at least three intervals of the entire movement of the main axis during the test process during the test process. Do the above -mentioned measurement measurement. The initial test power should be maintained at least 2S. Compliance with (GB/T 13634 specified level 1 standard measurement meter measurement).
2. Test of the head of the head; the diamond cone surface and the top spheres corresponding to the depth of the depth of 0.3mm should be polished. The combination of the two surfaces should be completely cut and there should be no surface defect. The shape of the head can be tested by directly measure or measures its projection on the projection screen. The measurement should be performed at least four equal intervals.
3. The calibration of the indentation depth measurement device; the indentation depth measurement device shall use the direction of the hardness value to generate the known increasing amount of movement, in the three intervals of no less than three intervals (including the low and low and low and the commonly used ruler. *Test on the interval corresponding to high hardness)
4. Test the test when test cycle. The test cycle time should be consistent with the test cycle specified in the GB/T 230.1, and the adjustment should be adjusted to cause the uncertainty within 0.5s.
1 When the hardness is not used for a long time, the dust cover is used to cover the machine.
2 Inject a small amount of motor oil into the contact surface of the screw and hand wheels on a regular basis.
3 Before using the hardness meter, the top surface of the screw should be cleaned.
4 If the hardness of the hardness shows a large error:
4.1 Get down the workbench to check whether it is cleaning with the touches with the screw;
4.2 Check whether the screw protective cover is up to the workbench;
4.3 Check whether the pressure head is damaged.
5 If the main test force is applied, the indicator pointer starts to rotate quickly, and then slowly rotates, indicating that the oil in the buffer is too small. At this time, the upper -end pad at the upper end of the buffer can be set into a clean 20#oil. At the same time, the handle is pushed many times to move the piston up and down many times to remove all the air in the buffer until the piston sinks to the end.
6 Use the standard hardness block carried by this machine to regularly check the hardness meter accuracy.
6.1 Wipe the workbench and standard hardness block, test on the hardness block working surface, and will never be allowed to test on the support surface.
6.2 If the value of the value is large, except for inspection according to the fourth item of this section, check whether the standard hardness block support surface has burrs.
6.3 When testing at different positions of the standard hardness block, the hardness block should be dragged on the workbench and should not be taken away from the workbench.
7 This instrument should be checked regularly and the verification is performed in a cycle.