• 博客等级:
  • 博客积分:0
  • 博客访问:1,222
  • 关注人气:0
  • 获赠金笔:0支
  • 赠出金笔:0支
  • 荣誉徽章:
正文 字体大小:


(2009-10-27 10:17:33)



Figure 1.72
Length changes of through-hardened, untempered 100 Cr 6depending on time and temperature. Initial state 20°C and I/I = 0 in volume. The total dimensional change is the net effect of the two volume changes (Figure 1.72).
通过硬化和未经锻造的100铬6的长度变化依赖时间和温度。初始状态20℃和I/I = 0
These dimensional changes are subject to the law of the smallest constraint. Tensional stresses, perhaps caused by an interference fit on the shaft, promote diameter increases. Rolling bearing manufacturers eliminate such dimensional changes by a defined tempering process after hardening. Retained austenite reduction and carbide precipitations in the martensite are anticipated by the tempering process. If bearings are not heated beyond the permissible maximum temperature (Table 1.7), the length changes illustrated in Figure 1.72 do not occur. Depending on the rolling bearing manufacturer, standard bearings are dimensionally stable up to 120 °C or 150 °C. The standardized stabilization grades of rolling bearings (Table 1.7) are guided by the highest operating temperature that occurs.
The values in the table apply to through-hardened rolling bearing steels, especially to through-hardened chromium steels. Dimensional changes may also 


Table 1.7 Dimensional stability of bearings
Suffix for dimensionally Maximum operating
stabilized bearings temperature (°C)
no suffix 120
S0 150
S1 200
S2 250
S3 300

无后缀 120
S0 150
S1 200
S2 250
S3 300
   Page 50

occur in surface layer hardened components which, as a rule, are tempered at low temperatures. The dimensional changes are caused by structural changes in the surface layer. At higher operating temperatures, each individual case must be checked to see whether a special stabilizing treatment becomes necessary. The loss in hardness of dimensionally stabilized bearings and at high temperatures must be considered in the load rating calculation according to Figure 3.13b.
Surface Treatment Processes 
For some time, substantial expenditure has been invested in the development of rolling bearing coatings. Some objectives of these surface treatment technologies are to improve the tribological behaviour (Section 4.3.6), sometimes obtained by coating the raceway surface of just one rolling contact partner; to increase the corrosion resistance; or to improve the insulation against electric current.
Black oxidizing or phosphatizing processes for improving the running-in behaviour or the capability to run without lubrication have been in use for quite a long time. A more modern process, tested in series applications, is the galvanic thin dense chromium coating (Figure 1.73). It improves the rolling contact fatigue behaviour and the wear resistance, especially under mixed friction conditions. Even after long running periods under rolling contact, reached with ideal lubricating conditions, the chromium layer must not peel. Due to the high hardness of the layer, peeled-off particles would quickly destroy the contact surfaces
An overall chromium coating improves the corrosion resistance of the generally used through-hardening rolling bearing steel. Coating by physical vapour deposition (PVD), coating by chemical vapour deposition (CVD) and surface layer modification by ion implantation, all three are being tested and are partly in use. Besides the technical criteria, the profitability of the bearing in question is decisive. Rolling bearing damage caused by the passage of electric current in special applications is eliminated by coating the outside diameters and faces of the bearing outer rings with insulating ceramic layers (Figure 1.74). These layers are applied by flame or plasma spraying.
1.2.2  Cage Materials
1.2.2  网箱材料
Rolling bearing cages are made of metal or plastic. Sheet steel or brass sheet are mainly used for the metal cages of smaller bearings; large and medium-size bearings have cold-formed or machined cages of brass or steel. Cages of bronze and aluminium alloy may be used for special applications.
For many years, rolling bearings of many types have been equipped with plastic cages. Thermoplastics have become important cage materials owing to their favourable sliding properties, their low weight and their elasticity; cages can be formed economically by injection moulding, even complicated shapes.
Most plastic cages are made of the glass-fibre reinforced, thermoplastic material polyamide 66 (PA66.GF) and are heat-stabilized. They are suitable for steady-state operating temperatures of up to 120 °C. If the bearings are lubricated with oil, the cage service life may be reduced by additives contained in the oil, and possibly aged oil at higher temperatures. Therefore, the oil change intervals have to be observed. The effect of the steady-state temperature on the cage life is shown in Figure 1.75 [291a, 253a].
塑胶保持架大部分是由玻璃纤维增强的热塑性材料聚酰胺66(PA66.GF),而且热稳定。它们适合用于稳态操作温度高达120 ° C的如果轴承油润滑,使用寿命保持架,可减少石油添加剂中,并可能在较高温度下岁的石油。因此,换油间隔必须得到遵守。稳定的关于保持架生活状态温度的影响如图1.75 [291a,253a]。

Figure 1.73
Surface of a thin dense chromium-coated rolling element at magnification × 1000
表面致密铬薄涂层滚动轴承在放大× 1000

Figure 1.74
Current-insulated deep-groove ball bearing
图1.74  电流绝缘深沟球轴承



阅读 评论 收藏 转载 喜欢 打印举报/Report
  • 评论加载中,请稍候...



    后一篇 >安明辉35,36

    新浪BLOG意见反馈留言板 电话:4000520066 提示音后按1键(按当地市话标准计费) 欢迎批评指正

    新浪简介 | About Sina | 广告服务 | 联系我们 | 招聘信息 | 网站律师 | SINA English | 会员注册 | 产品答疑

    新浪公司 版权所有