This article is dedicated to the alloy created by the jeweler - we are talking about the American Isaac Babbitt. It was babbitt, who brought the inventor in 1841 a prize of $ 20 thousand from the United States Congress, was a turning point in his career - the jeweler began to specialize in alloys. Babbit was already patented in Great Britain in 1844, and in the Russian Empire in 1847. What is valuable the brainchild of a scientist from the USA in the present, where it is used, how much it costs and what features it has, you will definitely learn further.
Babbitt - what is it
In honor of I. Babbitt, an alloy of three metals was named, which is most valuable in the production of bearings - the walls of the internal steel shaft of the part are poured with the melt of babbitt, along which friction occurs during rotation. The invention of an American scientist can significantly reduce bearing wear.
In the babbitt composition, tin, antimony, lead and copper are represented in different proportions. Since the metal babbitt consists of both soft and hard elements, it is distinguished by antifriction properties and wear resistance. Bearings made from it fit snugly against the shafts and are used for a long time.
The duration of proper operation of babbitt bearings directly depends on the thickness of the layer cast on a steel liner of this alloy. The thinner it is, the longer you can use the part.
Babbitt properties
We list the main remarkable properties of the alloy:
- antifriction material - resists frictions (reciprocating movements of the form "back and forth");
- resistance to corrosion;
- low hardness (HB 13-32);
- wear resistance;
- high thermal conductivity;
- underestimated melting point - 240-340 degrees Celsius;
- increased softness of the alloy at 100 degrees Celsius (HB 9-24);
- increased toughness.
Advantages and disadvantages of babbitt
Considering the properties of babbitt, we will touch on its key pros and cons. The advantages of the alloy include its anti-friction qualities and excellent running-in to the part. The alloy significantly increases the bearing life and wear resistance - during operation in the babbitt layer microchannels are formed, through which a lubricant enters the part.
One, but a significant drawback of babbits is their low strength compared to other alloys. Because of this, such a layer is limited to a stronger cast iron, steel or bronze body.
Varieties and brands of alloy
Varieties-brands of babbits are represented by three types - depending on the base metal:
- Calcium Although lead is its basis, the alloy got its name according to one of the components - calcium and sodium are also present in the composition. These elements distinguish this babbitt at the most inexpensive price, give it increased thermal conductivity and density. But at the same time, such an alloy oxidizes faster, which does not add to its wear resistance. Therefore, calcium babbitt in most cases is used in the liners of the frames of wagons, both freight and passenger - there they are most often checked and, if necessary, quickly replaced.
- Pewter . The basis of this babbitt is tin, which is characterized by a high coefficient of friction, high wear resistance and ductility, and increased corrosion resistance. This alloy is about twice as strong as its "brothers." Therefore, this brand of babbitt is indispensable for bearings, which have the maximum load and an important role. The scope of their application is various low-speed engines. In addition to tin, this alloy contains either cadmium and nickel, or antimony and copper. The only disadvantage of tin babbitt is its highest price among these alloys.
- Lead . The soft components here are lead and antimony - 87% and 13%, respectively, in this segment. The solid element of the alloy is crystalline antimony (5% of the total volume). This babbit is not distinguished by elasticity, and therefore it is used for the production of not the most loaded bearings. However, at the same time it is remarkable in that it tolerates the high-temperature heating of the element perfectly. It is worth noting that such babbits are more susceptible to corrosion than others. Their path is the diesel engines of tractors and cars.
The brands of lead babbitt are B16 (lead is the main element), BS6, BN (lead, tin, nickel, copper, arsenic, cadmium, antimony). They, like tin, are produced according to GOST 1320-74. Calcium alloys comply with GOST 1209-90; their varieties are BK2, BKA, BK2Ts, BK2Sh. Brands of tin babbitt - B83, B83C (a small addition of lead), B88. Variety B83, for example, is 80% of the tin component, 12% of antimony, 6% of copper and, on average, 0.1% of bismuth, lead, iron, arsenic, and aluminum. And B6 is 88% lead, 0.3% copper, 0.1% iron, a small fraction of zinc and arsenic.
Alloy production
The properties of babbitt directly depend on its components. For its production, it is only necessary to extract its elements (or recyclable materials), because he himself is a completely man-made alloy. The finished form of babbitt is ingots, ingots weighing no more than 22 kg. For their casting, the material is carefully prepared - cleaned, degreased. When melting from the surface of the mass remove the sprude - refractory foam.
Babbitt production ends with ingot casting. On each of them the company’s trademark, brand and smelting serial number are imprinted. Workers of a factory specializing in casting bearings melt finished babbitt ingots-briquettes and pour the melt into the bearing shell.
Babbitt melting
To obtain such alloys, both primary metals - primary ore, and secondary - remelting of scrap metal are used. In addition to the main components listed in the previous paragraphs, cadmium, arsenic, sodium, and tellurium are added to babbits.
Babbits B16, BN, B88 and others are cast into ingots (ingots), which differ in a strictly defined mass. It is also important that the smallest dirt is not observed on the surface of the ingot - even such a factor can adversely affect the quality of the bearing.
The brand of babbitt also affects the melting point of the alloy. So, the most popular B83 babbitt melts at a temperature of +240 degrees Celsius, and the tin B83 melts at + 340-440 degrees on the same scale.
The specifics of the babbit application
Each type of part requires its own brand of babbitt alloy:
- Connecting rod bearings (joint of the piston and crankshaft) - BM brand. Used for tractors. They require replacement with new ones after every thousand kilometers.
- Main bearings - the use of B88 babbitt, created specifically for high speeds, high dynamic loads. Therefore, this brand is successfully used for medium-speed and high-speed diesel engines.
- Bearings for water pipes, compressors - a type of BN, ideal for medium loads and speeds.
- Heavy engineering - the properties of babbit grade B16 are perfect.
Babbit value
Consider the cost of this alloy in the Russian Federation. The price directly depends on the properties of babbitt, on its brand. So, the average price of lead babbit B16 is about 350 thousand rubles / ton. The cost of the B83 grade alloy is about 1.3 million rubles / ton.
If we consider the market for recyclables, then 1 kg of babbitt scrap metal can be handed over for a maximum price of 500-600 rubles / kg. Basically, such alloys are bought for their subsequent disposal, because more unnecessary bearings can cause irreparable harm to the environment, since cadmium, lead, antimony are literally poisons for the nature around us.
Babbit alloys are far from a modern invention. However, even today they are still relevant in mechanics, namely in the production of bearings. This is due to the fact that it is babbits that are durable, wear-resistant, quickly and densely rub against a part, provide noiseless friction and, due to their low thermal conductivity, eliminate engine overheating. In addition, manufacturers offer dozens of different brands of babbits, each of which corresponds to a specific variety of both the bearing and the whole engine of the machine.