In order to produce alloy die castings to be efficient, reduce mold repair time,development and introduction of new hot working die materials, and themicrostructure and properties of die materials optimization by heat treatment,guardian of aluminum alloy forging common concern by surface treatment toprolong the service life of the die topic. In this paper, we discuss the weldingmelting loss phenomenon in aluminum alloy die casting mold and its preventive measures

Aluminium alloy forging Fang learned in each die casting cycle early, rapid heateffect of the mold cavity to withstand hot molten alloy, the work surface will produceheat of compression stress; be in the mold spray lubricant after casting, quench,which also produced in the surface tensile stress. In the alternating thermal suchunder stress, the mold surface will produce micro crack thermal fatigue, with the increase of die casting cycle times, the micro crack expand rapidly, somecentripetal expansion, the formation of crack. If the cracks around the same timeaccompanied by erosion and corrosion in molten alloy on the mold cavity, the mold surface will further damage, eventually resulting in early cracking of mould even scrapped.

Welding phenomena of 1 aluminum alloy in die casting die

In all the major causes of aluminum alloy die casting die failure, welding die surfaceoccurring problems began to get attention. "Bonding" is in the die casting industryterminology, it refers to between the die and the die casting alloy reaction. Once the occurrence of welding mold surface, will generate complex Fe-Al intermetallic compound phase, and cause defects on the surface of the casting die casting cyclein the next. The hard intermetallic phases will accumulate in the mold surface,therefore must interrupt the production and removal of weld produced materialused for polishing method, this will lead to the production of the extension of time,the waste of labor, but also reduce the service life of die.

Aluminium alloy forging Fang says usually according to the welding of different forms, can be divided into two kinds of "welding". The first welding form called"shock welding", namely bonding occurs in the mold surface facing the canalpouring or entrance cavity. These areas during the filling generally by the fierce impact of the molten metal flow, surface temperature is higher, under the pressure,the protective layer is easy to be destroyed, in the continuous erosion of die casting alloy mould protection layer failure and expose the metal base, alloy withsubstrate materials react to generate complex intermetallics. Intermetallic compound is hard deformation in die casting, it will not only lead to the rupture ofthe casting quality defects, and will take away the base material, and exposed fresh surface, so go round and begin again, welding phenomenon gradually deepened,serious when can cause the mold surface from corrosion and mould materialmelting loss. Therefore, must be promptly removed and the repair of damagedsurface at the early occurrence of welding. Second kinds of welding form called "deposition welding, welding position is to back away from the gate or runner.These areas are usually surface treatment or die lubricant can not reach the place.So their surface condition, temperature distribution, pressure situation different from other places. Aluminium alloy forging Fang said usually die casting alloyarrived in these regions after the temperature is low, the liquidity is poor, easy first solidification, in contact with the surface of semi solid alloy and die time hot longer,plus here to mould itself surface condition is not ideal, and therefore easy to formFeAl intermetallic compound, in times of die casting cycle, in these illiquid regiongradually deposited will intermetallic compounds, and finally the formation ofserious bonding effect of die casting production.

The composition of the bonding layer, are often complex Fe-Al intermetallic compounds, and because the composition of this layer of intermetallic compoundsis thin, so I have some difficulty in the analysis. But the researchers abroadZ.W.Chen and D.T.Fraser by using X ray diffraction generated on the dip of H13steel in molten aluminum alloy Al-11Si-3Cu intermetallic compounds in the structure were analyzed, they think, welding layer consists of a composite layer of intermetallic compound bcc- (FeSiAlCrMnCu), alpha six party alpha H- outer closelayer (Fe2SiAl8) the composition of intermetallic compound and the inner compactlayer orthorhombic -Fe2Al5 intermetallic compounds. And the Fe-Al interfaceorganization and the author they photographed the made of "in ADC12 die casting aluminum alloy immersed in Fe-Al interface morphology dipped in H13 steel" testobtained very similar.

The melting loss effect of 2 aluminum alloy die casting mold

Aluminium alloy forging Fang said by alloy melt, hot semi solid alloy scour, and keep the pressure aluminum alloy die casting die working condition in use after period of time, the surface of the protection layer of the general will form a reticularmicro crack, crack or even surface layer peeling. If the repair and maintenance ofdie surface are wrong, will place the so-called "melting loss" effect is more serious."Melting" refers to die at work after a period of time, the working face serious erosion, process makes the mold quality lighter. The melting loss is the role ofresults of comprehensive machinery die casting alloy for die-casting die a series ofcorrosion, erosion, erosion and welding.

The dissolution process of mold base material Fe in die casting aluminum alloy in the Fe-Al is a physical and chemical reaction and generate complex intermetallic compound process. At the same time, all kinds of alloy elements in the matrix will beinvolved in this reaction, and the intermetallic compound phase structure, reactionmechanism has not been clearly explained, only its general qualitative analysis. But because the melting loss reaction and on the surface of the mould occurs earlywelding has many similarities, so in case of melting loss region, often can find andweld formation of intermetallic compounds of similar material, the author in theexperiment of H13 steel to dip into the ADC12 die casting aluminum alloy, themelting loss occurred serious part sample.

Aluminium alloy forging Fang summary in view of the above we