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在货车实物铸件——20Л号钢铸造的自动车钩上进行的研究得出,在运行负载过程中在应力集中处特别是钩头向自动车钩钩尾框过渡区内会发生脆裂。钢在发脆的同时还会出现从该过渡区切取的试样拉力试验曲线图上屈服面积的消失,屈服极限提高,硬度增加,脆性临界温度向高温区偏移,抗断强度特性降低等现象,从而导致带有裂纹的自动车钩破损所需的力减小。这种脆裂发生在于标准运用条件下使用13～14年以上的车钩内。为了判定钢的发脆原因,分别从使用了3、7、13、16、20、25年的自动车钩过渡区(图1)切取了直径6毫米的5倍试样,并进行了拉力试验。钢的原始性能是在自动车
The research on the auto coupler made of the truck’s physical casting No.20 steel found that there is brittle fracture in the transition zone between the stress concentration place, especially the hook head and the auto coupler hook yoke during the operation load. Steel also appears brittle at the same time there will be taken from the transition zone tensile yield test sample curve disappears, the yield limit increased, the hardness increases, the critical temperature of brittle transition to high temperature, the characteristics of the reduced strength of the fracture , Resulting in a reduction of the force required to break the cracked auto coupler. This embrittlement occurs in the use of standard operating conditions for 13 to 14 years inside the coupler. In order to determine the cause of the brittleness of the steel, a 5-mm diameter specimen of 6 mm in diameter was cut from the auto-coupler transition zone (Figure 1) at 3, 7, 13, 16, 20 and 25 years, respectively. The original performance of steel is in the car