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Common defects and analysis of magnesium alloy castings

Date:2017-05-15    Browse times:    

A flux of slag

Defect characteristics:

1 Surface Flux: slag slag blocks were dark brown in the type shape, generally not too regular, small slag is difficult to find, can be dissolved by acid oxidation treatment before it.

2 castings generally white slag flux mixture dot in X optical film, on the surface is dark gray.

3 flux slag distribution in the lower part of the gate pouring position of casting within and near the corner.

4 after processing, exposed on the surface of the slag discharge flux in air for 1 ~ 4 hours you can see the brown spots, parked for a period of time, will grow white.

Cause of production:

1 process operation, pouring liquid alloy without static time, portable crucible or ladle will not smooth, after casting ladle or crucible residues too little, ladle in the crucible's alloy liquid, slag will stir in liquid alloy. Tools or crucible washing is not clean.

The use of 2 flux and modifiers: flux or modifying agent composition, preparation and storage do not meet the requirements for washing and thickening of too many times.

3 in the manufacture of tools, the welding quality is not good at the bottom of the pot type ladle or the bottom of the ladle.

Prevent method:

1 in the crucible's liquid alloy casting ladle with bottom layer and then gently pushing the flux, big scoop, scoop a metal to scoop next time not less than 4 minutes.

2 refining and modification to calm before pouring, no less than 15 minutes, and hit the net flux and slag, prohibit pouring, general spread of sulfur and fire extinguishing mixture of boric acid.

3 flux crucible temperature is not lower than 750~C, the use of tools and wash. After casting, upside down, all net leakage flux.

4 pouring out of the crucible to be smooth.

5 the use of qualified flux, and regularly check.

Two oxidation slag

Defect characteristics:

1 is located on the surface layer of the casting, which is distributed in the surface of the casting near the gate I. Sometimes a thin sheet of I rules with wrinkles on the clouds, the fracture is often yellow or brown.

2 along the wall thickness of casting a sandwich sheet [or penetrate the entire thickness; (also scattered), to the surface is a golden yellow or brown rhyolite. When the mouth is interrupted, it is often broken from the sandwich, and the oxidized wallet is in the.

3 the floc exists in the castings and thin-walled castings often exposed surface. The fracture surface is dark gray or black. Sometimes there is a small amount of flux.

Cause of production:

1 in the alloy smelting process to produce oxide caused by slag (also called a slag). The main charge is not clean, flux quality is not good, and the improper smelting process.

2 slag inclusions (also known as two slag inclusions), which are formed during the oxidation of the alloy during casting. Because of the unreasonable design of the pouring system, the preparation of the mould and the improper operation of the pouring process.

Prevent method:

1 a slag by pure charge, carefully refined, fully calm, to add a small amount of beryllium alloy (0001% ~ 0.00296) and other methods to eliminate.

Two 2 times the slag can be prevented by the following methods:

The correct design of the gating system: the expansion of gating system, as far as possible using the bottom note type or a vertical slot inside the gate, or by serpentine flat sprue, filtering net, steel wool filter dregs. For the large piece of the gate, the same thickness of the casting alloy component is arranged in the gate cup.

Casting alloy correctly, so that the straight gate is always full of metal, do not use a small ladle to pouring large, pouring in the gate cup and the surface of the cavity with a layer of dry sulfur and boric acid mixture of protective agent.

The correct control of other operations, to keep the sand moisture regulation, and uniformly Changchun real casting sand core to dry turtle control box and parking

Three crack

Defect characteristics:

1 hot crack, straight or zigzag slot split casting (penetrating crack) and cracks (non penetrating crack), crack section is strong oxidation of dark gray or black, no metallic luster, and split along the crystalline grain boundary edge. The medial thickness section junction and riser and the casting occurred in the casting corner connection hot spot.

2 cold crack, the appearance of a linear or irregular curve, metal fracture surface clean, metal surface cracks with metallic luster at the oxidation or slight oxidation of the cracks in crystal boundary, but the crystal.

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