Research On Centrifugal Casting Process And The Friction And Wear Properties Of The High Lead Tin-bronze Alloy

Bearings are important wear parts on large equipment in metallurgy, mining, electricity, etc., in the work they not only withstand greater pressure, shock loads and alternating stress, but also encounter the friction, the role of wear, high temperature and multi-corrosive effects of media types. Ordinary tin and lead Chiba’s base alloys, cast iron base bearing materials can not meet the requirements now. High lead tin-bronze alloys have excellent dry friction properties, high thermal resistance, fatigue resistance and anti-seizure properties, are widely used in the bearings.This paper reviews the current research progress of high lead tin-bronze alloy by centrifugal casting, summarized the key technology for preparing high lead tin-bronze alloys. The impact of centrifugal casting process such as centrifuge speed, pouring temperature, mold preheat temperature, casting temperatures, the content of lead and PbS to lead segregation, microstructure and properties of the high lead tin-bronze alloy were researched. and the optimum process conditions of preparation of high lead tin-bronze alloy by centrifugal casting was dertermined.The density, hardness and abrasive resistance of the high lead tin-bronze alloy by centrifugal casting has been tested, and observing and analyzing the microphotograph of alloys by SEM and metallographic microscope. Results show that:when PbS was not added, lead was lump or banded and it led to serious lead segregation. However, when PbS was added, compounds Cu2S were formed, which uniformly distributed on the grain boundary and increased incessantly being like a net, therefore they hindered the lead segregation. With the increasing quantity of PbS being added into, lead segregation became lighter and the grain refined gradually and the hardness was increased little by little. After3.0%PbS was added into high lead tin-bronze, the lead segregation was the lightest and the distribution was the most uniform, and what’s more, the grain was refined. The wear rate was increase and the friction coefficient was decrease and then tended to be increase as the loads increased to120N with the increase of the fixed loads at the friction speed of0.05m/s; similarly, the wear rate was increase and the friction coefficient was decrease and then tended to be stable as the friction speed increased to0.20m/s with the increase of the friction speed at the loads of100N; Then with the increase of the fixed loads and friction speed the solid lubrication film is damaged and the wear of the materials is severe and the wear rate unstably increases. In the process of friction and wear the Pb solid lubrication film on the worn surface is stable, and the materials have good antifriction and lower wear.