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Melting retrieving again of base bearing alloy smear metal of tin

27th September 2010 Bearing Technology 0 Comments

A preface

A lot of products need to use the alloy of bearing, such as body of cross head, slippery piece, piston, car engine, tractor in the compressor,etc. industrially. Produce it in the manufacture process, a large number of bearing alloy smear metal is usually sold at several yuan per kilogram as the waste material, and the finished price of the bearing alloy is up to 40 yuan / kg. If recycle the alloy smear metal of bearing, will reduce the cost of goods greatly, reduce the waste, help to improve the economic benefits of enterprises. This text melts retrieving research again to base bearing alloy smear metal of tin promptly.

2 cuts and melts and oxidizes lost analysis in the metal course

2.1 oxidizing while cutting

Base bearing alloy also famous tin base bar alloy of tin. This kind of alloy is difficult to be oxidized by the air at room temperature. Their mechanical performance is more numerously low than the mechanical performance of the steel material. So process it while cutting, should adopt the sharp tool and the rotational speed should be high. The temperature of smear metal processed like this will not be very high, the temperature only reaches 70 ℃- 100 ℃ in short-term, the alloy smear metal that comes out is still on and white, not alike the gloomy appeared after oxidizing. So, oxidizing and can blink while cutting.

2.2 melts metal oxidizing the loss while melting with the metal

The craft is lost on 2.2.1

No matter while melting or formulating the alloy, some metal losses because of producing and oxidizing the dreg mainly. In addition, and the loss caused by metal volatilizing, stewing the dreg, inclining to spatter etc.. While smelting the base bearing alloy of tin with the electric stove, the alloy is probably in 1.5% – 4% always lossing amount, add rosin, wait for organic matter make the intersection of tin and the intersection of base and the intersection of bearing and flux that alloy smelts, can be reduced and oxidized lossing.

Theoretical side on 2.2.2

The oxidizing of pure metal

Dynamics that the solid metal oxidizes is controlled by property of oxide formed. If the volume of oxide is smaller than turning into the metal volume that these oxides consume, oxidizing rate will not be become or all increased with hour. If the volume of oxide has exceeded the metal volume of turning into it, there is the replying and covering of close and continuous oxide film on the metal level surface melting, the oxidizing rate will press W2 =Kt this parabola relation reduced with growth of time. melts and merges gold oxidizing

Melting metal oxidizing the characteristic may change to some extent because of adding other elements. Will have priority to be oxidized with biggest element of oxygen affinity, the properties of oxide film that and this element produces are controlling the oxidizing process. Metal affinity in oxygen can hot decomposing pressuring, come on, judging by production of oxide of it generally. It is large that the production of oxide is hot, it is the smaller to decompose the pressure, just the stronger the affinity to oxygen of this metal is. Table 1 list copper, tin, the intersection of antimony and affinity to oxygen ‘ It is hot according to the production of oxide . Can find out in tin, antimony, copper, oxide of antimony turns into the biggest heat from Table 1, the affinity to oxygen of antimony is the greatest. In the base bearing alloy of tin, alloying element antimony will have priority to be oxidized, the properties of the oxide film produced are controlling the oxidizing process.

3 smear metal retrieves and smelts the craft

Table 2 lists the chemical composition of two kinds of representative tin base bearing alloy. Can be found out from Table 2, the principal ingredients of two kinds of alloy trade marks are antimony, copper and tin, lead, iron,etc. are the impurity. The impurity has influence greatly on that tin base uranium bears the performance of the alloy. The existence with plumbous trace, will appear made up by lead basic firm solution and tin base firm melting body and fusibly and wrap up the crystal melting point is 189 ℃ altogether in the alloy ,Thus worsen heat resistance and impact toughness of the alloy. The existence of micro- bismuth, there is altogether crystal to will present the melting point in the alloy, so should control strictly, otherwise the alloy is accidental and overheated in short-term, you will melt if you are some. Iron content exceed 0.1% o’clock, will form melting point in the alloy higher FeSn2 for the first time brilliant, worsen liquid flowability of alloy, will also make the alloy fragile, even produce the crackle, so the iron content in the alloy should be controlled strictly. Because the one that smelt all principal ingredients element in course oxidizes the speed differently, the principal ingredients element should be controlled within the range of stipulating the content too, adjust if necessary, could guarantee the mechanical performance of the alloy of bearing does not change. In order to achieve the the above-mentioned goal, the smear metal is retrieved should consider these points to smelt the craft:

If 3.1 make more than two types of bearings in the factory at the same time, must preserve the smear metal strictly separately, so as not to mix while smelting together. Can’t mix with the smear metal of other metal either, in case that while smelting and purifying, increase the difficulty of removing the impurity.

It is comparatively suitable that 3.2 smelts 50- 100 ℃ of crystalline temperature of beginning that the temperature is generally higher than the alloy. Such as the alloy of bearing ZChSnSb11-6 Smelt temperature should 430 ℃-480 ℃. It is too high to smelt the temperature, will lead to the fact crystalline grain of the alloy is thick, increase the alloy to oxidize and loss at the same time. Smelt hypothermia, can’t get tiny crystalline grain either, it is right to remove the impurity and unfavorable too at the same time.

3.3 smelts time and has something to do with the amount that includes the impurity in the power size of smelting pot and amount and alloy smear metal of smelting alloy smear metal quantity. In a word, after demanding to melt the liquid temperature evenly, have enough time to remove the impurity, adjust the content of every element in the alloy.

Difference between 3.4 ~s properties of utilizing the specific gravity between every material, melting point, ferromagnetic etc. of removing the impurity, adopt the appropriate craft method to remove the impurity.

Remove greasy dirt, inclusion, oxide in the smear metal on 3.4.1. While smelting the temperature and reaching over 200 ℃, the greasy dirt begins to volatilize, boil promptly, burn and remove subsequently. Remaining residue, inclusion, oxide can remove the latter out to can utilize the difference between metal and specific gravity of the two of suspended substance from the metal.

The metal uses the flux such as rosin in order to prevent the metal from oxidizing while smelting on 3.4.2, but the flux can be used for dispelling and melting the impurity suspended in the metal, except that angry or changes metal composition and crystallization to organize. If smelting the base bearing alloy smear metal of tin, add some chlorine ammonia NH4Cl ,Can remove the alloy and melt iron element and inclusion in the liquid,etc.. The response type is:

The ammonia, hydrogen or vapor produced form a lot of small bubbles in the metal liquid, hang oxidizing inclusion, absorbing in the companion above rising meeting they, turbid, or is ejected upward against by the bubble rising the level surface and is removed.

It is ferromagnetic to utilize to remove the impurity on 3.4.3. Such as the clearance of the casting iron, steel particulate. The usable steel is the magnetized material, can be attracted strongly by the magnetic field. And tin base the intersection of bearing and alloy to resist magnetized material, magnetic field being faint to repel. If tin the intersection of base and the intersection of bearing and the intersection of alloy and smear metal and iron filling mix together, can remove the iron filling before not smelting smear metal with better magnetic field. Can be found out from the table, the principal ingredients of two kinds of alloy trade marks are antimony, copper and tin, lead, bismuth, iron,etc. are the impurity. The impurity has influence greatly on performance of the base bearing alloy of tin. The existence with plumbous trace, will present the fusible bag made up by lead basic firm solution and tin base firm melting body in the alloy.

3.5 is smelted should check, analyze whether the alloy principal ingredients accorded with the content of the trade mark of this alloy before finishing. If a certain main element is scarce, can add this metal into the alloy to smelt while melting the liquid, or reduce the metal with reducing agent. Can act as reducing agent of copper with boron magnesium, its response type is: 6Cu2OMg3B2

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