Vulcanized powder metallurgy products
Objective (a) of vulcanizedVulcanization process in powder metallurgy products as anti-friction bearing material applied powder metallurgy, iron-based oil bearing the most widely used. Sintered oil-bearing (including the amount of graphite 1% -4%) manufacturing process is simple, low cost, under PV <18 ~ 25 kgcm m / cm 2 · sec situation, can replace bronze, babbitt and other friction-reducing material. But under heavy operating conditions, such as high friction surface sliding speed and load larger units, the sintered parts wear resistance and life will rapidly decrease. In order to improve anti-friction porous iron base friction-reducing properties of parts, reduce the friction coefficient and improve the working temperature to expand the scope of its application, the use of vulcanization process is a worthy way.
Sulfide sulfur and most have some lubricating properties. Is a kind of good iron sulfide solid lubricant, particularly under dry conditions, the presence of iron sulfide, with good seizure resistance.
Iron-based powder metallurgy products, using its pores may be impregnated quite a lot of sulfur, sulfur and heated iron can pore surface of iron sulfide, which is evenly distributed throughout the product plays a good lubrication on the friction surface effect, and can improve the cutting performance. After the vulcanized products, friction and cutting surface looked very smooth.
Porous sintered iron sulfide after treatment, the most prominent role is a good dry friction properties. In the oil-free operating conditions (that is, or can not be allowed to refuel refueling), it is a satisfactory self-lubricating material, and has good seizure resistance and reduce the phenomenon of bite-axis. In addition, the friction properties of this material and the general anti-friction material is different. Usually material than the pressure increases, the friction coefficient begins to change little when the pressure ratio exceeds a certain value, a sharp increase in the coefficient of friction. And through the porous sintered iron sulfide after the treatment, the friction coefficient increases its pressure ratio than the pressure in a wide range increased but decreased. This is a valuable anti-friction material characteristics.
After the curing process of sintering iron-based oil bearing, can successfully work in the following 250 ℃.
(B) curing Process
Vulcanization process is relatively simple, does not require specialized equipment, the process is as follows:
Sulfur placed in a crucible and heated to melt, the temperature control in the 120 ~ 130 ℃, the sulfur flow at this time is better, if the temperature is too high, is not conducive to dipping. The need impregnated sintered article preheated to 100 ~ 150 ℃, then the article is immersed in molten sulfur was immersed for 3 to 20 minutes, not been pre-impregnated article 25 to 30 minutes. Depending on the density of the article, the wall thickness and to determine the required amount of immersion immersion time. Low density, wall thickness of immersion time may be less; and vice versa. Dip After removing products, shed the remaining sulfur. Finally, the impregnated products into the furnace, hydrogen-protection, can also be protected with charcoal, heated to 700 ~ 720 ℃ incubated 0.5 to 1 hour, at this time, sulfur and iron immersed in the role of iron sulfide. 6 to a density of 6.2 g / cm 3 article, sulfur enters about 35 to 4 percent (by weight). In order to make immersed heating firing is part of pores formed iron sulfide sulfur.
After the curing process of sintered products, can be oiled and finishing and other treatment.
Application (c) Examples of the vulcanization process
1, the hub sleeve flour machine installed in two ends of the roll, a total of four sets. A pressure of 280 kg roller, the rotational speed of 700 to 1000 rev / min (P = 10 kg / cm 2, V = 2 m / sec). Original tin bronze bushings with rejection oil ring lubrication. Now switch to a density of 5.8 g / cm 3, S containing an amount of 6.8% instead of porous sintered iron, no need for the original lubricating device before driving just a few drops of oil, continuous 40 hours, the temperature was about 40 ℃ sleeve ; 12,000 kg flour mill, the sleeve is still working properly.
2, small cone drill cone drill sleeve is an important tool for oil drilling, oil drilling at the top of this there is a slide shaft sleeve, that is a lot of pressure (pressure P = 500 kgf / cm 2, the speed V = 0.15 m / s ), and a strong vibration and shock.