Fasteners, hardness index

by:MPS     2020-08-03
< P> hardness said against hard objects the ability of its surface. It is one of the important performance index of metal materials. Generally, the higher the hardness, wear resistance, the better. Commonly used hardness index have brinell, rockwell and vickers hardness. < / P> < P> 1。 Brinell hardness ( HB) < / P> < P> at a certain load ( General 3000 kg) To a certain size ( To 10 mm in diameter) Hardened steel ball pressure into the material surface, keeping a period of time, to load, load with indentation area ratio, is the brinell hardness number ( HB) , the unit is kg force/was ( N /平方毫米) 。 < / P> < P> 2。 Rockwell hardness ( HR) < / P> < P> when HB> 450 or sample hours, brinell hardness test and will not be used to switch to rockwell hardness measurement. It is with a diamond cone apex Angle 120 ° or diameter of 1. 59, 3. 18 mm steel ball, under certain load down into the material surface under test, the hardness of materials by indentation depth. According to different experimental material hardness, the three kinds of different scale to say: < / P> < P> HRA: is 60 kg load and drill coup-de-point forcer for hardness, used in high hardness materials ( Such as cemented carbide, etc. ) 。 < / P> < P> HRB: is a 100 kg load and the diameter of 1. 58 mm hardened steel, hardness, low hardness material ( Such as annealing steel, cast iron, etc. ) 。 < / P> < P> HRC: is a 150 kg load and drill coup-de-point forcer for hardness, used in high hardness materials ( Such as hardened steel, etc. ) 。 < / P> < P> 3。 Vickers hardness ( HV) < / P> < P> to within 120 kg load and apex Angle of 136 ° diamond square forcer pressure cone into the surface of materials, materials of the indentation indentation surface area divided by load value, is the vickers hardness values ( HV) 。 < / P> < P> from the mentioned above, the vickers hardness is one kind of surface hardness. There is a conversion relation between it and other hardness. < / P> < P> means the surface hardness, hardness material inside is no hardness requirement. Only mechanical performance requirements, Tensile strength, yield strength and impact toughness) 。 < / P> < P> GB / T3098。 I don't see any surface hardness of 1-2000? 5. 6 shows that the surface hardness, isn't it? - surface hardness should not be higher than the core hardness vickers hardness (30 About 3 HRC) 。 10. 9 the surface hardness of should not be greater than 390 hv0. 1. 3. As for no surface hardness requirements that's low level of performance, such as 3. 64. 64. 85. 65. 86. Eight, because there is no heat treatment, so there is no requirement, because he surface hardness is mainly cold heading or baked after cutting stress generated by the hardness. < / P> < P> when bolt hardness, bolts without heat treatment, only need to do surface hardness in the qualified range. If it is heat treatment bolt will be without the cut a large of the diameter of the surface hardness, hardness testing in 1/2 r, on the surface of the hardness up to the standard. < / P> < P> it has a surface of a core, surface refers to float in removing surface rust after use vickers or rockwell hardness, surface core to remove 1/2 diameter long ministry department in surface and core after 1/2 of hardness, the difference between the two hardness cannot exceed 30 HV, 30 HV show higher surface carburizing, is not allowed, if the surface decarburization on the surface of low more than 30 HV show, is also not allowed. To look at the 3098 carefully. < / P> < P> < / P>
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