Selecting Bronze Bearing Materials

Bearing DesignMaterial PropertiesThe Bearing Bronze FamiliesSummary

It is not at all unusual to come across a bronze sleeve bearing that has been performing satisfactorily for decades, even under severe operating conditions. In fact, a properly designed and maintained bronze bearing often outlasts the equipment it serves. Achieving such performance is not difficult, but it requires sound design, the right bearing material, accurate manufacture and, as with any mechanical equipment, diligent maintenance.

Bronzes are unquestionably the most versatile class of bearing materials, offering a broad range of properties from a wide selection of alloys and compositions. This data sheet describes the most used standard bearing bronzes and is aimed at helping the designer select the right bronze for the job at hand.

Bearing Design

良好的轴承设计涉及三个基本要素:了解服务环境,设计适当的润滑,并为工作选择最佳轴承材料。准确评估预期的服务条件不能过分强调;这是所有后续决策的基础。创建或至少识别轴承将运行的润滑模式同样重要。有时可以通过设计建立模式;其他次是通过操作条件简单地决定。

Finally, the bearing material selected must suit both the service environment and the operating mode. The wide array of properties offered by the bearing bronzes simplifies material selection process and helps insure that the alloy chosen will provide optimum bearing performance.

Service Conditions


The most important prerequisite to assuring optimum bearing performance is knowing - or accurately predicting service conditions. Major areas of consideration are:
  • Load, steady and impact,
  • Speed at design load,
  • 振荡运动,即少于全旋转,
  • Corrosive environments,
  • Dirty environments and/or lubricants,
  • Temperature,
  • Frequent start-stop operation,
  • 可疑或可中断的润滑剂供应,
  • Shaft or journal misalignment,
  • Hardness differential, bearing vs. shaft.

Satisfying the often conflicting demands of the particular mix of operating conditions expected makes almost every bearing design a compromise. Conditions involving extremes of load, speed or temperature in combination, whether low or high, are especially challenging. The bearing designer's task is to optimize that compromise to achieve the best possible performance in the finished product.

Operating Modes


Having defined the bearing's operating conditions the next step is establishing the in-service lubrication mode - hydrodynamic, boundary or mixed film. Sometimes this can be done by design, other times it must be accepted by default.

流体动力学模式

The mode offering the lowest friction and least wear is called hydrodynamic or full-film operation. In this mode the bearing is completely separated from the shaft (Journal) by a continuous film of oil in the eccentric space between shaft and bearing (Figur e1). The oil is under hydrodynamic pressure created by the relative motion between bearing and journal. Hydrodynamic conditions are established by:

  • 图1.在操作条件下套筒轴承的偏心位置。 Figure 1。偏心位置开放下的滑动轴承rating Conditions. Full-film mode denoted by finite value of h.
  • Velocity greater than 25 sfpm,
  • Unidirectional motion (no oscillation),
  • Proper lubricant viscosity (higher viscosity increases load-carrying capacity, lower viscosity decreases the frictional coefficient), and
  • Proper lubricant flow: flow must be continuous and not less than the minimum level approximated by the expressions:
    Q1= 29.3 x 10-9L + 0.0043 W/D mD2N, gpm
    Q1= 3.32 x 10-3L 0.0043 W/D mD2N, drops per min
    1 cu cm = 30 drops
    C- Radial clearance, inches
    D- Journal diameter inches
    e- Eccentricity or radial journal displacement,
    E- Journal eccentricity ratio
    L- Bearing length, inches
    m- 清关因素
    N- Rotation speed -RPM
    Q1- Minimum oil flow for full film
    W- Steady load - to be supported, lb
    Z- Lubricant absolute viscosity, centipoise.

A sleeve bearing's operating mode is described in terms of a bearing characteristic number. A. The value of A, in relation to other factors, determines whether or not the bearing will operate hydrodynamically. The characteristic number is calculated by means of the equation:

A= m2W/D2ZN

in which,
m= 1000 * 2C/D

and where,
C= radial clearance, in inches,
Z= absolute lubricant viscosity centipoise.

这称为清关因素,它以2C / D编写的总径流间隙,并且包括乘法器1000,即保持数字易于管理。

If load, speed and other factors can be adjusted such that A falls between 0.0005 and 0.50 the bearing should operate in the full-film mode. A bearing and its journal operate in practice with a given eccentricity, i.e., with the shaft positioned slightly off the bearing's true center by a distance, e, (Figure 1). We can then define an eccentricity ratio, E, as:

E= E / c
E= journal eccentricity ratio
e= eccentricity or radial displacement of journal in.

This enables us to construct a diagram in terms of A, E and the bearing's L/D ratio. That diagram,Figure 2, is popularly known as the "heart-shaped curve" because of its shape. It delineates areas based on A, E and the L/D ratio which dictate the operating mode. Bearings which fall inside the heart-shaped area will operate in the fullfilm or hydrodynamic mode. Those outside it will not, however those near the heart may operate under partial hydrodynamic conditions, as explained below.

Figure 2。The "Heart-Shaped Curve" Delineating Operation in the Full-Film or Hydrodynamic Mode.

通过将所有因子锗达到共同轴承配置的桌子的可用性,设计师的作业已经大大简化了。这些已被编制为铸造青铜液动力套筒轴承性能桌子,可从铜开发协会公司获得超过90,000个轴承条件。爱游戏 意甲爱游戏中心下载安装

由于轴承和期刊不联系我n the hydrodynamic mode, frictional coefficients can be as low as 0.001. (This is equivalent to the level attained by a high-precision ball element bearing and is considerably better than that achieved with roller bearings.) Also, since there is no metal-to-metal contact there can be no wear and bearing life should be indefinite. Theoretically, the only important material property consideration for full-film bearings is that the bearing alloy be strong enough to support the applied load. At start-up, (or shut-down) however, there is insufficient velocity to establish full-film operation immediately. This means the bearing at least momentarily operates outside the hydrodynamic regime, and there may be actual brief metal-to-metal contact. Extremely abrupt changes in load or lubricant viscosity can have the same effect. Hydrodynamic bearings normally can sustain changes in load or shock loads up to ten times the design load for limited periods of time.

Boundary Lubrication Mode


The most demanding condition from the bearing material standpoint is when the bearing and shaft actually touch or are separated only by a microscopically thin film of oil. This is the boundary film mode of operation. Boundary-film conditions exist when:
  • Bearings are grease-lubricated,
  • Bearings are only periodically lubricated as by hand oiling or greasing,
  • Motion is reciprocating (oscillating), or
  • Surface velocity is less than 10 sfpm.

Bearings operating under boundary conditions demand the greatest care in material selection. The bearing alloy must have low inherent friction, it must resist welding and seizing and it should have high thermal conductivity to remove frictional heat from the bearing surface.

Mixed Film Mode


Between the hydrodynamic and boundary regimes lies a condition known as the mixed-film mode. Here, a portion of the bearing's surface is supported by a hydrodynamic oil film while the rest operates with metal-to-metal (or boundary film) contact. This is probably the most common of the three operating modes.

Material Properties

Many millions of bearings operate successfully in the boundary and mixed-film modes for their entire service lives. The only penalty this entails is an increase in friction compared to hydrodynamically lubricated bearings and a consequently higher energy expenditure. Bearing life, however, will depend very heavily on the choice of bearing material. Even hydrodynamic bearings pass through boundary and mixed-film modes during start-up, and shut down, or when faced with transient upset conditions. This means that material selection is an important design consideration for all sleeve bearings, no matter what their operating mode. The general attributes of a good bearing material are:

  • A low coefficient of friction versus hard shaft materials,
  • Good wear behavior against steel journals (scoring resistance),
  • 吸收和丢弃小污染物颗粒的能力(戒烟性),
  • The ability to adapt and adjust to the shaft roughness and misalignment (conformability),
  • High compressive strength,
  • High fatigue strength,
  • Corrosion resistance,
  • Low shear strength (at the bearing-to shaft interface),
  • Structural uniformity, and
  • Reasonable cost and ready availability.

然而,在这些时期内,材料的固有摩擦特性非常重要,但是当轴承在边界模式下操作时,这是简要的。低摩擦系数是材料抗焊接抗焊接的一个因素,因此得分,钢轴。用于钢的铜绿币的摩擦系数0.08和0.14。在磨损期间,或者当存在绝对没有润滑剂时,摩擦系数可以为约0.12至高达0.18至0.30。相比之下,钢上铝磨损过程中的摩擦系数为0.32,钢上的钢是1.00。

虽然通常努力保持轴承及其润滑剂清洁,但一定程度的污染几乎是不可避免的。良好的轴承材料应该能够通过将小型污垢颗粒嵌入其结构中,使它们远离钢轴,否则可能会刮伤。

Likewise, there is always a danger that shafts can be misaligned, or not be perfectly smooth. A bearing alloy may therefore be called upon to conform, or "wear-in" slightly to compensate for the discrepancy. This property is called conformability: it is related to the material's hardness and compressive yield strength. A high yield strength is also related to good fatigue resistance. Together, these properties largely define the material's load-carrying capacity.

对于在侵略性环境中运行的轴承中的轴承,或者对于长时间保持空闲的轴承,需要足够的耐腐蚀性尤为重要。因此,良好的耐腐蚀性增加了使用寿命和保质期。

A bearing material should have structural uniformity and its properties should not change as surface layers wear away. On the other hand, alloys such as the leaded bronzes are used because they provide a lubricating film of lead at the bearing/ journal interface. Lead has a low shear strength, and is able to fill in irregularities in the shaft and act as an emergency lubricant if the oil supply is temporarily interrupted.

最后,轴承材料应具有成本效益,并在短时间内获得。在所有这些属性中没有单轴承材料擅长,这是轴承设计始终涉及妥协的原因之一。然而,青铜轴承合金提供了这种广泛选择的材料特性,其中一个可以始终符合特定设计的需求。

The Bearing Bronze Families

The bearing bronzes are listed inTable 1by their UNS alloy designation with standard specifications covering each. The seventeen bearing bronzes listed fall into five alloy families with similar compositions and properties. The tin bronzes rely mostly on tin for their strength; leaded tin bronzes additionally contain modest amounts of lead for better antifrictional properties, but at the expense of some strength; highleaded tin bronzes have the highest lubricity but the lowest strength, aluminum bronzes and manganese bronze serve applications which require their extremely high strength and excellent corrosion resistance. Members of each family have similar properties, with differences among family members allowing selection based on economic considerations or on the need to tailor alloys for particular applications.

Table 1。铸造青铜轴承合金规格
ALLOY ASTM. SAE AMS 米尔 FED
C90300 B271
B505
B584
J461,
J462
(formerly 620)
C-15345,ALLOY 8
C-22087
C-11866,COMP.26
C-22229.
QQ-C-390
C90500 B271
B505
B22.
B584
J461,
J462
(formerly 62)
4845 QQ-C-390
C90700. B505 J461,
J462
(formerly 65)
QQ-C-390
C92200 B271
B505
B61
B584
J461,
J462
(formerly 622)
C-15345,ALLOY 9
B-16541
QQ-C-390
C92300 B271
B505
B584
J461,
J462
(formerly 621)
C-15345,ALLOY 10
B-16540
QQ-C-390
C92700. B271
B505
J461,
J462
(formerly 63)
QQ-C-390
C93200 B271
B505
B22.
B584
J461,
J462
(以前660)
C-15.12,ALLOY 12 QQ-C-390
C93400 B505 C-15345,ALLOY 11
C-22087
C-22229.
QQ-C-390
C93500 B271
B505
B584
J461,
J462
(formerly 66)
QQ-C-390
C93700 B271
B505
B22.
B584
J461,
J462
792
(formerly 64)
4827
4842
QQ-C-390
C93800. B271
B505
B66
B584
J461,
J462
(formerly 67)
QQ-C-390
C94300 B271
B505
B66
B584
J461,
J462
4840 QQ-C-390
C95300
c95300ht.
B271
B505
B148
J461,
J462
(formerly 688)
C-11866,COMP.22 QQ-C-390
C95400
C95400HT
B271
B505
B148
J461,
J462
4870
4871
4872
4873
C-15345,ALLOY 13
C-11866,COMP.23
QQ-C-390
C95500
C95500HT
B271
B505
B148
J461,
J462
C-15345,ALLOY 14
C-22087
B-21230
C-22229.
QQ-C-390
C86300 B271
B505
B22.
B584
J461,
J462
4862 C-15345,ALLOY 6
C-22087
C-11866,COMP 21
C-22229.
QQ-C-390
C86400 B271
B505
B584
QQ-C-390

Tin Bronzes: Alloy Nos. C90300, C90500, C90700

Tin's principal function in these bronzes is to strengthen the alloys. (Zinc also adds strength, but more than about 4% zinc reduces the antifrictional properties of the bearings alloy.) The tin bronzes are strong and hard and have very high ductility. This combination of properties gives them a high load-carrying capacity, good wear resistance and the ability to withstand pounding. The alloys are noted for their corrosion resistance in seawater and brines.

锡四铜的硬度抑制它们容易遵守粗糙或未对准的轴。同样,它们不会均匀地嵌入污垢颗粒,因此必须与清洁,可靠的润滑系统一起使用。它们需要300-400 BHN之间的轴硬度。锡龙杆润滑脂润滑比其他龙头更好;它们也非常适合界面膜操作,因为它们能够形成具有小痕量润滑剂的极性化合物。

锡隆中机械性能的差异并不伟大。有些含有锌作为增强剂,符合更昂贵的锡。

Leaded Tin Bronzes: Alloy Nos. C92200, C92300, C92700


有些锡青铜含有少量的铅。在this group of alloys, lead's main function is to improve machinability. It is not present in sufficient concentration to change the alloys' bearing properties appreciably A few of the leaded bronzes also contain zinc, which strengthens the alloys at a lower cost than tin. The leaded bronzes in this family otherwise have similar properties and application as the tin bronzes.

High-Leaded Tin Bronzes: Alloy Nos. C93200, C93400, C93500, C93700, C93800, C94300


The family of high-leaded tin bronzes include the workhorses of the bearing bronze alloys. Alloy C93200 has a wider range of applicability, and is more often specified, than all other bearing materials. It, and the other high-leaded tin bronzes are used for general utility applications under medium loads and speeds, i.e., those conditions which constitute the bulk of bearing uses. Strengths and hardnesses are somewhat lower than those of the tin bronzes but this group of leaded alloys excel in their antifriction and machining properties.

As with other bearing bronze families the differences among individual alloys are minor. Alloy C93200 utilizes a combination of tin and zinc for cost-effective strengthening while C93700 relies solely on tin to obtain the same strength level. In addition to its good strength, Alloy C93700 is known for its corrosion resistance to mildly acidic mine waters, and to mineral waters and papermill sulfite liquors. Wear resistance is good at high speeds and under high-load, shock and vibration conditions. The alloy has fair casting properties, something to be considered when large or complex bearing shapes must be produced. Alloy C93700 contains enough lead to permit use under doubtful or interruptible lubrication, but it must be used with hardened shafts. The lead addition makes these alloys easy to machine.

High strength is sacrificed for superior lubricity in the bronzes containing 15 and 25 percent lead, Alloys C93800 and C94300. These high-leaded tin bronzes embed dirt particles very well and conform easily to irregularities in shaft surfaces and permit use with unhardened shafts. As in all leaded bronzes the lead is present as discrete microscopic particles; in alloys C93800 and C94300 there is ample lead available to smear onto the journal to prevent welding and seizing, should the lubricant supply be interrupted. The lead also provides excellent machinability.
Because of their comparatively lower strength and somewhat reduced ductility Alloys C93800 and C94300 should not be specified for use under high loads or in applications where impacts can be anticipated. They operate best at moderate loads and high speeds, especially where lubrication may be unreliable. They conform well and are very tolerant of dirty operating conditions, properties which have found them extensive use in offhighway, earthmoving and heavy industrial equipment.

Aluminum Bronzes: Alloy Nos. C95300, C95300-HT, C95400, C95400-HT, C95500, C95500-HT, C95510


The aluminum bronzes are the strongest and most complex of the copper-based bearing alloys. Their aluminum content provides most of their high strength and makes them the only bearing bronzes capable of being heat treated. Their high strength, up to 68,000 psi yield and 120,000 tensile, permits them to be used at unit loads up to 50 percent higher than those for leaded tin bronze Alloy C93200.

Because of their high strength, however, they have fairly low ductility and do not conform or embed well. They consequently require shafts hardened to 550-600 BHN. Surfaces must also be extremely smooth, with both shaft and bearing finished to 1520 in RMS. Careful attention should be given to lubricant cleanliness and reliability, the latter because these alloys do not have the anti-seizing properties typical of the leaded and tin bearing bronzes. On the other hand, the aluminum bronzes have excellent corrosion resistance and are ideally suited for such applications as marine propellers and pump impellers. The aluminum bronzes also have superior elevated temperature strength. They are the only bronzes - and the only conventional bearing material able to operate at temperatures exceeding 50OF.

Manganese Bronzes: Alloy Nos. C86300, C86400


锰铜器是Muntz金属型合金(60%铜40%锌黄铜)的修饰,含有锰,铁和铝,加上润滑性,抗癫痫和嵌入性。爱游戏中心下载安装像铝烫金一样,它们与优异的耐腐蚀性相结合。锰青铜轴承可以在重负载下高速运行,但需要高轴硬度和非粗糙的操作条件。

Summary

轴承青铜器提供范围广泛的力量,ductility, hardness, wear resistance, anti-seizing properties, low friction and the ability to conform to irregularities, tolerate dirty operating environments and contaminated lubricants. The corrosion resistance of bearing bronzes is generally superior to other bearing materials, and can be selected to meet particular ambient conditions. Bronzes permit easy and economical manufacture, allowing bearings to be made in special and one-of-a-kind configurations simply and at low cost. No bearing metals have better machinability than the leaded and high-leaded bearing bronzes. Almost without exception, a bearing bronze can be selected to satisfy any bearing application that exists.

This publication, based on available data, has been prepared for the information and use of professionals in the industry. CDA assumes no responsibility or liability in connection with this publication and makes no warranties of any kind with respect to the information contained herein.