The sampling position of the hardness sample of the grey cast iron cylinder block is shown in Figure 1. The hardness test at the cylinder position requires 3-4 hardness tests at equal intervals to test whether the hardness distribution at the cylinder is uniform.
The hardness of the cylinder barrel shall be tested by hb-3000b small load Brinell hardness tester. The size of the sample block shall be prepared in accordance with GB / t231.3-2012 metallic materials Brinell hardness test Part 3 – Calibration of standard hardness blocks. The sample block shall be ground and polished before the test, The surface shall be flat and smooth, free of oxide skin and external dirt, and the surface roughness Ra shall not be greater than 1.6 μ M. The load of Brinell hardness test is 30kgf and the holding time is 10s. The indentation diameter is measured for many times and then the average value is removed. Finally, the results are queried through GB / t231.4-2009 metallic materials Brinell hardness test Part 4: hardness value table.
During the structural analysis, we also need to test the hardness of different tissues. At this time, the sample hardness is measured by hmv-2 micro Vickers hardness tester. The sample treatment before measurement is the same as the above. The test load is 0.2kgf and the holding time is 10s.
2.Tensile strength test
The tensile strength test of grey cast iron is carried out on cmt5105 microcomputer controlled electronic universal testing machine, and the tensile rate is 2mm/min. The preparation of tensile samples is single cast and processed according to the requirements of standard cylindrical samples in JB / t7945-1999 test method for mechanical properties of grey cast iron, as shown in Figure 2, The roughness of the clamping part of the end face can be slightly higher to prevent slipping during stretching. D0 ＝ 8mm, l0 ＝ 40mm, D1 ＝ 12mm, L1 ＝ 25mm in the figure, with a total length of 100mm. Two samples of each type shall be tested, and the rate of tensile test shall be 2mm / min.