Aluminum alloy die casting die for the welding melting loss phenomenon
Mold is a modern large-scale industrial production important equipment, generally through the die casting forming material of aluminum, magnesium, zinc, which is more than 80% of aluminum alloy China mould die castings.While in the aluminum alloy die casting, and about 80% are used in the automotive mould industry, so China mould automotive industry technology trends will about die-casting mold manufacturing and production .
In recent years, with China's automobile mould industry development, the automobile aluminum magnesium alloy die castings demand increases.Therefore, considering the large volume, low cost, efficient production of alloy China mould die castings, at the same time to reduce the mold repair time, the development and introduction of new material for hot working die, and through optimization of heat treatment for die material structure and performance, and through the surface treatment to extend its service life has become a vast number of materials research focus.
Die casting process, the injection mould cavity filling time is generally 0.1s, or even less, alloy through the gate with a speed of about 40 ～ 60m/ s, some even as high as 200m/ s. Metal solidification pressure intensity usually in about 40 ～ 120MPa. In aluminum alloy die casting, die-casting mold surface temperature can be up to 500 ～ 600 ℃.For the manufacture of a small part of aluminum alloy, the casting solidification circulation time of about 3 ～ 6S, large aluminum alloy parts is not more than 90s.
Aluminum alloy die casting die of welding phenomenon
In all result in aluminum alloy die casting mold and the main cause of the failure, mold surface welding problems began to get attention."Bonding" is in the die casting industry terminology, it refers to the mold and die casting alloy reaction between.The mold surface once welding, can generate complex Fe-Al intermetallic compounds, and at the next die casting cycle in the casting surface defect.Hard metal are also in the mold surface accumulation, therefore must discontinue production and polishing method to remove welding product, this will lead to the production of the extension of time, the waste of labor force, but also reduce the mold life.
Usually in a welded in different forms, can be divided into two kinds of "welding".The first welding form called "impact welding", namely welding occurs in the injection mold surface toward the cavity entrance or inside the runner.These regions in the filling process are generally subject to a flow of molten metal in the fierce impact, surface temperature is higher, the pressure, the protective layer is easy to destroy, in die casting alloy continuous erosion protection layer under the die failure and the bare metal, alloy and the matrix material back should generate complex intermetallic compounds.Intermetallic compound is hard not easy deformation in die casting, it will not only result in broken off quality of casting defects, at the same time will take the matrix material, and exposing fresh surface, so go round and begin again, welding phenomenon gradually deepened, will lead to serious mold surface by corrosion and the mold material melting loss.Therefore, must occur in the welding of early timely removal and repair damaged surface.Second kinds of welding form called "deposition welding", namely welding position back to or away from the sprue gate.These areas are usually surface treatment or die lubricant can reach places.Therefore their surface condition, temperature distribution, pressure and other places in different.Usually die casting alloy at these regions after the temperature is low, the liquidity is poor, easy first solidification, hot semi solid alloy and die surface contact time, and here the mold itself surface condition is not very ideal, therefore is easy to form FeAl intermetallic compounds, several times in the casting cycle, intermetallic compound in these illiquid regional deposited gradually, finally form the serious effect of welding, die casting production.
Although in the aluminum alloy die casting die of different regions will have different forms of welding, the welding but has some universal common features -- namely the mold surface welding region generally showed a silver luster.