According to the ISO 6507 / ASTM standard E384 vickers hardness test
Vickers hardness testIs ideal for all metal testing, so this method is the most widely used.vickersHardness test methodIn the standardThe ISO 6507(metal materials - vickers hardness test - part 1: test method) andASTM E384(vickers and knoop material micro indentation hardness standard test method) are described.
Vickers hardness test procedureVickers hardness calculationTest force imposedMinimum distance indentation testAdvantages and disadvantagesVickers hardness tester
The basic information of the vickers hardness test
Vickers test methodUsed in the pressure head is a diamond of a pyramid, with square base on the side with the alpha = 136 ° Angle one vertex.Test, the test by applying force (according to the test standard, begin from 10 g) will be the head pressure on the sample, and according to keep time to maintain it.
In optical way of measuring residual indentation test the length of two diagonals.Then, according to the average diagonal and applied to calculate the test forceVickers hardness.
In accordance with ISO 6507 standard vickers hardness test procedure
In optical methodVickers hardness testThe measuring head left indentation size (diagonal).And in depth measuring method, measuring pressure head caused by the indentation depth (rockwell method through standardized only).
Under the specified test force, pressure head on the workpiece surface impression left by the (sample), the greater the tested material, the more soft.
In order to determineIn accordance with ISO 6507 standard vickers hardness (HV), which need to be specified test load (starting from 1 gf) will be sprayed head (interface Angle is 136 °) pressure into the sample (artifacts).
The calculation of vickers hardness
- Vickers hardness (HV)By applying the test force (F, measured in newtons N) and the residual indentation of the sample surface area of the business (see the following formula).To calculate residual cone surface area of the indentation, need to use the average of the two diagonals d1 and d2 (in mm), because the bottom area of the vickers indentation are often not completely is a square.
- Recommended by the vickers hardness range is available in standard (The ISO 6507Found in).According to the test force and different sample materials, vickers hardness value can vary between 1 to 3000 HV.
Test force imposed
- Ideally, the test force increased from 0 in 7 seconds to its final value (the minimum possible measurement uncertainty).In the standard allows exert the maximum time interval for 2 to 8 seconds (nominal duration of 7 s).
- Usually, the test force of the residence time of 10 to 15 seconds (nominal duration of 14 s).If stay longer, it must also be specified in the hardness value duration (in seconds), for example: 610 HV 10/30 (residence time of 30 s).
- Vickers method generally used in macro scale test force than brinell method used in the test force is much smaller.Preferred for macro scope, 49, 98, 196, 294, 490 or 980 N, 294 N the most commonly used in the actual test.
In accordance with ISO 6507 standard vickers test method of minimum distance test points
The ISO 6507In the standard set forVickers test methodThe test point (indentation) and to the minimum distance between minimum distance on the edge of the specimen.Set the minimum distance is to avoid the hardness test results the distortion caused by deformation of material structure.
According to the standard must comply with the minimum see left-hand chart.
The advantages and disadvantages of using the vickers hardness test test method
Vickers method has the following advantages:
- Vickers method can be used for any materials and samples (from soft to hard), because the program covers the entire hardness range.
- There is only one type of pressure head, apply to all vickers method.
- Non destructive testing can be done, so the sample can be used for other purposes.
Vickers method has the following disadvantages:
- Because want to optical measurement of indentation, so the surface of the sample quality must be good.This means that must be prepared to test position (after grinding and polishing), otherwise it is difficult to precise evaluation.
- This is a rather slow process (compared with rockwell method).Test period between 30 to 60 seconds, not including the preparation of sample time.
- Due to the need to assess the optical impression, vickers hardness tester must be equipped with optical system, so the living cells-recognition hardness meter is more expensive.
- Generally speaking, although need to sample preparation and evaluation of hardness value very laborious, but it can be said that the vickers method still relies on the diversity of its application is becoming the most commonly used test method in practice.
