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本文作者测量了锻制的和工业烧结的T42高速钢的硬度、抗压强度、杨氏模量,抗弯强度和断裂韧性。将锻制的和烧结的材料经过相同的热处理以后,发现它们的硬度(800～1010HV50),杨氏模量(～220GNm~(-2))和断裂韧性(9～18MNm-3/2)无很大差别。在锻制材料上取样作四点弯曲试验,按其加工方向纵向切取试样的强度稍高于横向切取试样的强度(1.3—2.4GNm~(-2)),并且这两种试样的强度都明显地高于烧结材料的强度(1.0～1.2Gm~(-3))。用实验室烧结的材料作三点弯曲试验,其脆性断裂应力为1.9～3.0GNm~(-2),该值可与锻制材料的脆性断裂应力相比。在锻制材料中含有碳化物带和分散的粗大MC碳化物,而在烧结材料中可以发现许多微孔和不完全连接区域,虽然这些情况是不常见的。锻制材料的断裂源主要是从一粗大碳化物或碳化物聚集区开始的,而烧结材料的断裂源主要是从微孔上开始的。试验室烧结材料中的微孔一般比工业烧结材料中的微孔要小。这些裂纹的尺寸与用临界裂纹分析估算出来的裂纹尺寸基本一致。仅仅少数烧结的试样有显微裂纹的痕迹,而锻制的试样则没有。所检测到的这些裂纹都发生在细小的微孔处或域连接薄弱的区域,锻制的T42钢中的粗大碳化物和烧结的T42钢中的大微孔已经是断裂产生的临界尺寸,因此,未曾发现显微裂纹。
The authors measured the hardness, compressive strength, Young’s modulus, flexural strength and fracture toughness of forged and industrially sintered T42 HSS. After being subjected to the same heat treatment, the as-made and sintered materials were found to have hardness (800-1010 HV50), Young’s modulus (-220 GNm -2) and fracture toughness (9-18 MNm -3/2) Very different. Samples were taken from forging materials for four-point bending test, the strength of specimens cut longitudinally according to the processing direction was slightly higher than that of specimens cut horizontally (1.3-2.4GNm -2), and the specimens of The strength is obviously higher than that of the sintered material (1.0 ~ 1.2Gm ~ (-3)). Three-point bending tests with laboratory sintered materials show a brittle fracture stress of 1.9-3.0 GNm -2, which is comparable to the brittle fracture stress of forged materials. Carbide bands and dispersed coarse MC carbides are present in the forging material, and many pores and incompletely connected regions are found in the sintered material, although these are not common. The source of the forging material is mainly from a coarse carbide or carbide agglomeration zone, and the source of the fracture of the sintered material is mainly from the micropores. Micropores in laboratory sintered materials are generally smaller than those in industrial sintered materials. The size of these cracks is basically the same as the crack size estimated by the critical crack analysis. Only a few sintered samples showed signs of microcracking whereas the as-forged samples did not. These cracks were detected at the tiny pores or weakly connected areas. The coarse carbides in the as-fabricated T42 steel and the large pores in the sintered T42 steel were already the critical dimensions for fracture initiation No microcracks were found.