Powder metallurgy processing bearings how to improve the wear resistance?
The vulcanization process, powder metallurgy products
The purpose of (a) vulcanization processing
Vulcanization process in powder metallurgy products rolled as anti-friction material liner applications, with the application of iron base oil bearing is the most widespread. Sintering oil-retaining bearing (graphite content 1% – 1%), simple manufacturing process, low cost, in PV < 18 ~ 25 kg · m/cm 2 · s situation, but instead of bronze, babbitt anti-friction and show advertisements on a oil bearing
The vulcanization process, powder metallurgy products
The purpose of (a) vulcanization processing
Vulcanization process in powder metallurgy products as friction material of powder metallurgy bearing applications, with the application of iron base oil bearing is the most widespread. Sintering oil-retaining bearing (graphite content 1% – 1%), simple manufacturing process, low cost, in PV < 18 ~ 25 kg · m/cm 2 · s situation, but instead of bronze, the anti-friction material such as babbitt. But under the condition of heavy work, such as high sliding velocity and unit load on friction surface is larger, the wear-resisting performance and life of the sintering parts will reduce rapidly. In order to improve the antifriction performance of porous iron-based antifriction parts, reduce the friction coefficient, improve the working temperature to expand the scope of its use, adopt the method of vulcanization processing is a worth extending.
Most sulfur and sulfide has certain lubrication performance. Iron sulfide is a kind of good solid lubricant, especially under the condition of dry friction, the existence of iron sulfide, has the very good resistance to bite.
Powder metallurgy iron-based products, can use its wool stoma dipping quite a lot of sulfur, the heat can make the sulfur and iron iron sulfide generated on the surface of the pore, it evenly distributed in the products everywhere, on the friction surface has good lubrication, and can improve the machining performance. After vulcanization processing products, and its friction and cutting surface is very smooth.
Porous sintered iron after vulcanization process, was the most prominent role has the very good dry friction performance. Under the working conditions of oil free (i.e., not allowed to go or not go), is a satisfactory self-lubrication material, and has good resistance to bite, reduce on shaft. In addition, the material of the friction characteristics different from general anti-friction material. General materials with the increase of pressure, the coefficient of friction to change is not big, when pressure exceeds a certain value, friction coefficient has increased dramatically. And after vulcanization process of porous sintered iron, its friction coefficient over a wide range than the pressure with the increase of the pressure down instead. This is a valuable features of anti-friction material.
After vulcanization treatment of sintered iron base oil bearing, can work under 250 ℃ successfully.
(2) the vulcanization process
Vulcanization processing technology is simple, do not need special equipment, the process is:
Will sulfur into the crucible melting, heating temperature control during 120 ~ 130 ℃, the liquidity of sulfur is better, if the temperature is too high, is not conducive to dip. Will need to be impregnated sintered products to preheat to 100 ~ 150 ℃, then put the products into the liquid sulfur melting, dipping 3 ~ 20 minutes, without preheat products impregnation 25 ~ 30 minutes. Depending on the products, the density of wall thickness and the required in quantity to determine the dipping time. Low density, wall thickness of the dipping time is less; And vice versa. Take it out of the dip products, flow to the best of the rest of the sulfur. Finally, put varnished products charging, hydrogen protection, protection, also can use charcoal heating to 700 ~ 720 ℃ heat preservation 0.5 ~ 1 hour, at this point, the immersion of sulfur and iron iron sulfide. For the density of 6 ~ 6.2 g/cm 3 goods, amount of sulfur in about 35 ~ 4% (weight percentage). Heating roasting is in order to make the pore formation of iron sulfide sulfur into parts.
After vulcanization process of sintered products, can be oiled and finishing processing.
(3) the vulcanization processing application, for example
1, flour machine shaft sleeve The shaft sleeve is installed on both ends of two roll, a total of four sets. Roller pressure is 280 kg, speed is 700 ~ 1000 RPM (P = 10 kg/cm2, V = 2 m/s). Used in tin bronze sleeves, with oil lubrication. Now switch to the density of 5.8 g/cm 3, porous sintered iron instead of S content of 6.8%, can need not the original lubricating device, only need to add a few drops of oil before driving, continuous work 40 hours, bushing temperature 40 ℃ or so; Grinding flour 12000 kilograms, collar still work normally.
2, small rock drill collar Rock drill is an important tool for oil drilling, the drilling with a sliding shaft set at the top by pressure (pressure P = 500 KGF/cm2, speed V = 0.15 m/s), and have a strong vibration and impact.
Second, the baptism of powder metallurgy products oil processing
Powder metallurgy porous oiled anti-friction products is an important process, increases the corrosion resistance of powder metallurgy products, improve the wear resistance and prolong its service life. Oiled processing after sintered iron base oil bearing, lubricating oil into the products in the pore, namely when the axis of rotation, with the set of kinetic friction, heat production, make the bearing temperature rise, oil in thermal expansion, from the pore flow between shaft and shaft sleeve automatic oil supply, the formation of oil film lubrication anti-friction effect. Oiled also can prevent products by oxidation.
Oil immersion method can be divided into ordinary oiled, heating oil and vacuum oiled.
Normal oiled: put clean the sintering products in the oil (oil) for 20 ~ 30 commonly soak. Under the action of capillary force, oil in products into the pore to the products. This method, low efficiency of oiled, oil immersion time is long, need a few hours, used in the products of oil content is not high.
Heating oil bath: put clean sintered products in 80 ~ 120 ℃ in hot oil soak for 1 hour. Due to the products, heating the air inside the open pore expand, make part of the air be ruled out. After cooling, the rest of the air and contraction, put the oil into the pore. Because of the hot oil liquid, high lubricity, and thus can be more oil immersed into the products. The immersion method efficiency is higher than ordinary oil leaching rate.
Vacuum oiled: clean up of the sintering products in vacuum box, sealed fit to – 720 – mm Hg, then to vacuum box into the oil, and then heated to 80 ℃, 20 ~ 30 minutes. Due to the air pumped out the products open pore, the oil can be in 10 minutes into products. This method is high efficiency, high speed immersed.
Another kind of form, this method is to first put the vacuum the air in the cabinet with our products, and then pass into the chamber of the preheating of oil and products cover up, again through the chamber and atmosphere and oil into the products pore is faster.
Third, waxed
General porous powder metallurgy products have features, such as contact with air interface is larger, prone to corrosion phenomenon, especially coastal rainy areas, air humidity is big, products of corrosion is more serious. In some cases, not only the products surface from corrosion, even will be affected by the internal surface of open pore corrosion, seriously affect its performance, and even cause scrap.
In order to prevent and reduce the corrosion of ferrous products, also must be after the oiled surface coated wax, to isolate products contact with the outside world. Long-distance transportation in products or a long time to save (according to regulations, products within six months may not rust), does not rust.
Wax coating is powder metallurgy products, put the wax wax cylinder, heated to 60 ~ 80 ℃, the wax melts, will clean products into wax liquid, and immediately took out, namely in the products surface evenly coated with a layer of wax, cool rear can packaging.
La fluid is composed of paraffin and petroleum jelly, according to different season have different proportion. After add vaseline liquid wax is the purpose of dry fastness, from cracking. Vaseline can add less, when high temperatures are low can increase the ratio of vaseline appropriately. Use vaseline commonly 20%, 80% of paraffin.
Four, packaging
Appropriate packaging, is in order to protect the powder metallurgy products from damage, deterioration in the process of storage, transportation, is the last procedure in the production of powder metallurgy. If the packing is bad can lead to the loss of the final product, should say it’s a pity.
Packing method is: after products coated wax, anti-rust paper, the several pieces of wrapped into a box, carton should be put on the certificate and operation instruction. Outside the box indicate the factory name and address, product name, model and quantity, product size and specifications. Cut not model products with different specifications and mixed by mistake. And then will be several boxes into a carton, box must be fitted around the moistureproof paper, weight must not exceed 50 kg per box. Outside the box should indicate the factory name and address, product name, model, specification and quantity. Should indicate the date of packing at the same time, the last labeled “handle with care, pay attention to moistureproof” tag.
