热处理论坛

 找回密码
 注册

QQ登录

只需一步,快速开始

扫一扫,访问微社区

北京中仪天信科技有限公司 爱思科仪器有限公司 江苏益科热处理设备有限公司
搜索
查看: 4131|回复: 2

[Discussion] Interpreting Carburized Case Depths

[复制链接]

签到天数: 165 天

[LV.7]常住居民III

发表于 2014-8-17 10:04:06 | 显示全部楼层 |阅读模式
北京中仪天信科技有限公司
本帖最后由 jixieman 于 2014-8-17 11:53 编辑

As part of suggested guidelines for designers, it was recommended that hardness on drawings be specified as Rockwell “C’’ with a minimum spread of 5 points or as a minimum hardness value, again in Rockwell C. The statement was then made that if total case depth is less than 0.76 mm (0.030 inch), an accurate reading cannot be obtained on “C” scale because a 150-kg load will drive the penetrator through the case and into core material, giving a false reading. Various Rockwell scales were recommended (Table 1) for use with minimum total case depths. The question was, “How accurate is this data?” Table1.jpg

评分

参与人数 1热处理币 +5 收起 理由
cjzhou + 5 good topic!

查看全部评分

签到天数: 165 天

[LV.7]常住居民III

 楼主| 发表于 2014-8-17 11:52:05 | 显示全部楼层
UNDERSTANDING HARDNESS TESTING OF CASE-HARDENED PARTS

In general, there are four controlling factors in the selection of the proper scale for hardness testing, namely type of material (chemistry and hardenability), thickness of the specimen, width of the area to be tested and scale limitations. It is this last factor that is often open to interpretation.

    In the case of Rockwell C, typical applications (per ASTM E18) include “deep case-hardened steel.” In the case of Rockwell A, its use includes “shallow case-hardened steel.” These statements, while interesting, do not in and of themselves tell us if the data in Table 1 is correct.

    The regular or superficial Rockwell scales are established such that an infinitely hard material will read 100 on the diamond penetrator scales (or 130 on the ball penetrator scales). Thus, one regular Rockwell number represents a penetration of 0.002 mm (0.000080 inch). Therefore, a reading of 60 HRC indicates penetration (from minor to major load) of 100 – 60 = 40 x 0.002 = 0.08 mm (0.0032 inch). By contrast, in Rockwell superficial testing, one superficial Rockwell number represents a penetration of 0.001 mm (0.000040 inch). Therefore, a reading of 90 HR15N indicates penetration from minor to major load of (100 – 90) x 0.001 = 0.01 mm (0.0004 inch).[2] However, Rockwell superficial testing, due to the lighter applied load, has a greater margin for error, which is why Rockwell C or Rockwell A testing is preferred.
回复 支持 反对

使用道具 举报

签到天数: 199 天

[LV.7]常住居民III

发表于 2014-8-22 15:58:59 | 显示全部楼层
本帖最后由 oliver 于 2014-8-29 00:03 编辑

Discussion:

    I don't think the Rockwell scale recomended on Table 1 is correct to test surface hardness on case hardened parts.
    For example, when case depth is more than 0.76 mm and "C" scale is used, even penitrator may not drive through the case, the case might collapse since the core is lower carbon and soft. That will cause inaccurate reading.
    HV scale should be more proper to recomend for testing surface hardness on case hardened parts.

评分

参与人数 1热处理币 +20 收起 理由
cjzhou + 20 感谢参与!

查看全部评分

回复 支持 反对

使用道具 举报

您需要登录后才可以回帖 登录 | 注册

本版积分规则

苏州工业园区热海热处理设备有限公司 热处理论坛合作伙伴广告位 苏州出兴自动化设备有限公司

QQ|Archiver|手机版|小黑屋|热处理论坛 ( 苏ICP备11036679号 公安机关备案号:32059002001695 )

GMT+8, 2020-3-28 22:38 , Processed in 0.048271 second(s), 28 queries .

Powered by Discuz! X3.4

Copyright © 2001-2020, Tencent Cloud.

快速回复 返回顶部 返回列表