Prevent the surface defects of aluminum alloy die-casting parts

Prevent the surface defects of aluminum alloy die-casting parts

With the advantages of aluminum alloy die casting gradually emerging, the demand on the market continues to require processing plants to increase production efforts, in order to upgrade the old iron casting products into aluminum alloy or magnesium alloy as soon as possible. In this way, the task of the processing plant is heavy, and the quality must be maintained. Today xiaobian will teach you how to prevent some common aluminum alloy die-casting defects.

One, the pull mode Characteristics and inspection method: the surface of the casting along the direction of the open mold, with a certain depth, and severe facial scars. The other is the metal liquid and mold adhesion, adhesion and strain, so that the surface of the casting more material or lack of material. Cause: 1, the surface of the cavity damage (collapse or knock). 2, the direction of the release deviation is too small or inverted. 3, the top out is unbalanced, the top deviation. 4. High pouring temperature and high mold temperature lead to the adhesion of the alloy liquid. 5, the effect of the release agent is not good. 6, aluminum and gold iron contain less than 0.6%. 7, the type cavity rough is not smooth, the mold hardness is low.

Preventive measures:

1. Repair the damaged parts of the mold surface, correct the slope of the die release, improve the hardness of the mold (HRC 45 ° ~ 48 °), and improve the smoothness of the mold.
2. Adjust the top bar to make the top balance.
3. Replace the release agent with good release effect.

4, adjust the alloy iron content.

4. Reduce the pouring temperature, and control the stability and balance of the mold temperature.

6. Adjust the direction of the inner gate to avoid metal liquid into the core and wall.

Two, air bubbles Characteristics and inspection methods: the surface of the casting has uplift of different sizes, or holes are formed under the skin. Causes:

1, the metal liquid in the pressure injection chamber is filled with too low (control in 45%~70%), easy to produce curly gas, the initial pressure firing rate is too high.

2, the mold pouring system is unreasonable, bad exhaust.

3, melting temperature is too high, gas content is high, melt is not removed.

4, the mold temperature is too high, the mold retention time is not enough, the metal solidification time is insufficient, the strength is not enough to open the mold too early, and the pressure gas expands.

5. Excessive dosage of mold release agent and injection head oil.
6. The blowing time after spraying is too short, and the surface water of the mold is not blown dry.

Preventive measures:

1. Adjust the switching points of die-casting process parameters, pressure firing speed and high-pressure firing speed.

2, modify the mold pouring channel, add overflow tank, exhaust tank.

3, reduce the mode temperature of the defect area, thus reducing the pressure effect of the gas.

4, adjust the melting process,

5, extend the mold retention time, adjust the blowing time after spraying.

7. Adjust the dosage of mold release agent and pressure ejection oil. Three, crack Characteristics and inspection methods: the surface of the casting has straight or irregular and narrow lines, which has a development trend under the action of external force. Cold crack- -the cracked metal is not oxidized.

Hot crack- -the metal is oxidized at the crack place. Reasons:

1, the alloy in the high iron content or silicon content is too low.

2. The content of harmful impurities in the alloy is too high, which reduces the plasticity of the alloy.

3, aluminum silicon alloy: aluminum silicon copper alloy contains zinc or excessive copper content; excessive magnesium content in aluminum magnesium alloy.

4. The mold temperature is too low.

5. The wall thickness of the casting changes dramatically, and the shrinkage is blocked.

6, the mold retention time is too long, large stress.

7, uneven force. Preventive measures:

1. Correct control of alloy composition, in some cases, pure aluminum ingot can be added to the alloy to reduce the magnesium content in the alloy; or add aluminum silicon intermediate alloy to increase the content of silicon.

2, change the casting structure, increase the round Angle, increase the slope of the release, reduce the wall thickness difference,

3, change or increase the top position, so that the top out force is uniform.

4, shorten the mold opening or core extraction time.

5, increase the mold temperature (mold working temperature 180° - -280°).

Four, deformation Characteristics and inspection methods:

the die casting geometry does not consistent with the drawing.

Overall deformation or local deformation. Reasons:

1. The casting structure design is poor, resulting in uneven shrinkage.

2, the mold is too early, the casting rigidity is not enough.

3, pull mode deformation.

4, the top rod setting is not reasonable, when the top out of the force is not uniform.

5, Improper gate removal method.

Preventive measures:

1. Improve the casting structure.
2. Adjust the mold opening time.
3. Set the position and number of the jacking rod reasonably.
4. Choose a reasonable gate gate removal method.
5. Eliminate the drawing factor.

Five, leave the mark and the decorative pattern Features and inspection methods:

appearance inspection, the casting surface has the stripes with the same direction of the metal liquid flow, there are obvious visible lines different from the metal matrix color without direction, no development trend. Reasons:

1, the first into the metal liquid of the cavity to form a very thin and incomplete metal layer, is made up by the later metal liquid and left traces.

2. The mold temperature is too low.

3, the inner pouring mouth cross-section area is too small and the improper position produces the splash.

4, insufficient pressure acting on the metal fluid.

5, pattern: excessive amount of paint and injection oil.

Preventive measures:

1, raise the temperature of the mold.

2. Adjust the cross-sectional area or position of the inner pouring gate.

3. Adjust the metal liquid speed and pressure of the inner pouring.

4, choose the appropriate paint, injection oil and adjust the amount of paint injection oil.