Bending strength refers to the ability of materials to bend and crack continuously. HT150 has certain mechanical strength and good shock absorption. It is generally used and manufactured parts bearing medium stress; Therefore, its bending performance has a great impact on the overall performance of the workpiece. According to the national standard (GB / T 14452-93), the bending strength of gray iron castings directly produced by water slag iron smelting was tested.
Take the material with the wall thickness of 45mm of gray iron casting for the experiment, and use the rectangular cross-sectional interview sample for the experiment. Due to the clamping problem of the testing machine, cut the gray iron casting material into 6.5 x 6.5 non-standard samples on the on-line cutting machine, and then grind or mill it to RA3 two μ M or below, as shown in Figure 1 (the method of cutting and sampling blank and machining shall not change the bending mechanical properties of the material). The sample is carried out on the universal material testing machine (we 300). The experiment adopts the three-point bending test device (its principle is shown in Figure 3). Before the experiment, the span of the sample is 28mm measured with a vernier caliper. By stretching the sample, pay attention to the changes of the sample and pointer during the gradual loading of the sample. When the sample breaks under compressive stress (the fracture morphology is shown in Figure 2), stop loading immediately and record the data required for the experiment.
The principle of three-point bending test is shown in the figure below:
Figure 4 shows the variation of sample displacement with stress during the three-point bending strength test:
According to the relationship between displacement and stress in the bending process of the sample in Figure 4, the sample has been in an elastic state during the bending experiment. When the applied load exceeds the yield limit of the sample, the sample breaks, and there is almost no plastic deformation of the sample in the whole process.
According to the calculation formula of bending strength of three-point test:
According to the national standard (GB / t9439 1988), the tensile strength of gray iron rectangular sample (as shown in the table) HT150, the bending strength of gray iron casting TB = 150 ~ 250 MPa; 325.75mpa far exceeds the minimum shear strength TB = 150 ~ 250 MPa specified by HT150.
Through the test of tensile properties and bending resistance of gray iron castings directly produced by water slag iron smelting, it can be concluded that the mechanical properties of this sample have reached the national standard of gray iron, which proves that the mechanical properties of HT150 gray iron castings directly produced by water slag iron smelting fully meet the requirements of gray iron castings.