10 major defects of die-casting aluminum alloy and its prevention
专栏:Industry information
发布日期:2016-01-19
阅读量:632
作者:佚名
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one. Flow marks and patternsAppearance inspection: There are stripes on the surface of the casting that are consistent with the flow direction of the molten metal. There is a visible non-dir..........
one. Flow marks and patterns

Appearance inspection: There are stripes on the surface of the casting that are consistent with the flow direction of the molten metal. There is a visible non-directional texture that is different from the color of the metal matrix, and there is no development trend.

1. The causes of flow marks are as follows:

(1) The mold temperature is too low.

(2) Poor design of the runner and poor position of the gate.

(3) The material temperature is too low.

(4) The filling speed is low and the filling time is short.

(5) The pouring system is unreasonable.

(6) Poor exhaust.

(7) The spray is unreasonable.

2. The reason for the pattern is that the coating in the cavity is too much or the quality of the coating is poor. The solution and prevention methods are as follows:

(1) Adjust the cross-sectional area or position of the gate.

(2) Increase the mold temperature.

(3) Adjust the speed and pressure of the gate.

(4) Appropriate selection of coatings and adjustment of dosage.

Two. Reticulated wing (tort crack)

Appearance inspection: There are traces of protrusions or depressions on the surface of the die-casting part, which are continuously enlarged and extended as the number of times of die-casting increases.

The reasons are as follows:

(1) There is a crack on the surface of the die-cast cavity.

(2) The pre-heating of the die-casting mold is uneven.

The solution to and prevention is:

(1) After the die-casting mold is to be periodically or die-casted for a certain number of times, it shall be annealed to eliminate the stress in the cavity.

(2) If a crack has appeared on the surface of the cavity, the surface should be ground and the crack layer removed.

(3) The mold should be preheated evenly.

three. Cold partition

Appearance inspection: The surface of the die-casting part has obvious, irregular, and depressed linear type lines (both penetrating and non-penetrating). The shape is small and narrow, and sometimes the mating edge is smooth, and there is a possibility of disconnection under the action of external force.

The reasons are as follows:

(1) The two metal streams are butted together, but not completely fused without inclusions, and the bonding force of the two metals is weak; (2) the pouring temperature or the temperature of the die-casting mold is low;

(3) The runner is not in the correct position or the flow path is too long;

(4) The filling speed is low.

The solution to and prevention is:

(1) Properly increase the pouring temperature;

(2) Increasing the injection ratio to compress the short filling time and increasing the injection speed.

(3) Improve exhaust and filling conditions.

Four. Concave (dent)

Visual inspection: There are smooth dents (like dishes) on the surface of most of the thickness of the die-cast part.

The reasons are as follows:

(1) caused by shrinkage

1.1 The design of the die casting is not too good;

1.2 The sprue is not in the proper position;

1.3 The injection pressure is lower than the pressure, and the pressure holding time is short;

1.4 The local temperature of the die-casting mold is too high.

(2) The cooling system design is unreasonable;

(3) The mold opening is too early;

(4) The pouring temperature is too high.

The solution to and prevention is:

(1) The wall thickness should be uniform;

(2) The transition of thickness should be moderated;

(3) Correctly select the introduction position of the alloy liquid and increase the cross-sectional area of the inner runner; (4) increase the injection pressure and prolong the pressure holding time;

(5) Properly reduce the pouring temperature and the temperature of the die-casting mold;

(6) local cooling to local high temperature;

(7) Improve the overflow conditions;

Fives. Imprint

Visual inspection: Traces left by contact between the surface of the casting and the surface of the die-cast cavity or step marks on the surface of the casting.

The reasons are as follows:

1, caused by the ejection element

(1) the end face of the jack is worn;

(2) The length of the ejector adjustment is inconsistent;

(3) The splicing part of the die-casting model cavity is not well matched with other parts; 2. It is caused by splicing or moving parts

(1) The part of the inlay is loose;

(2) Loose or worn parts of the activity;

(3) The side wall surface of the casting is formed by inserts that are interspersed with each other by moving and fixed molds.

The solution to and prevention is:

(1) The length of the ejector should be adjusted to the proper position;

(2) Fastening inserts or other moving parts

(3) Eliminate sharp corners during design and fit with gap adjustment;

(4) Improve the structure of the casting so that the die-casting mold can eliminate the interspersed insert form and improve the structure of the die-casting mold; Adhesive trace

Appearance inspection: small pieces and metal or non-metal and metal base parts are welded together, and the small pieces are peeled off under the action of external force. Some of the surface of the cast after peeling is bright and some are dark gray.

The reasons for this are as follows:

(1) There are metal or non-metallic residues on the surface of the cavity of the die-casting mold; (2) Impurities are attached to the surface of the cavity when pouring.

The solution to and prevention is:

(1) Before the die casting, the cavity pressure chamber and the pouring system should be cleaned to remove metal or non-metallic adhering substances; (2) the cast alloy should also be cleaned;

(3) Choose a suitable coating and the coating should be uniform.

Seven. Layering (skinning and peeling)

Visual inspection or damage inspection: There are obvious layers of metal in the casting.

The reasons for this are as follows:

(1) The rigidity of the mold is not enough. During the filling process of the molten metal, the template is shaken; (2) the punching phenomenon occurs during the injection process;

(3) The sprue system is not properly designed.

The solution to and prevention is:

(1) Strengthen the rigidity of the mold, tighten the mold parts to make it stable; (2) Adjust the cooperation between the injection punch and the pressure chamber to eliminate the creep phenomenon; (3) Reasonably design the inner runner.

Eight. Friction ablation

Visual inspection: The surface of the die casting produces a rough surface at certain locations.

The reasons for this are as follows:

(1) The position and shape of the gate caused by the die-casting type (mold) are improperly oriented; (2) The cooling of the molten metal portion at the gate runner due to the casting condition is insufficient.

The solution to and prevention is:

(1) Improve the position and direction of the sprue for poor internal pouring; (2) Improve the cooling conditions, especially to improve the violent part of the molten metal; (3) Add paint to the ablated part;

(4) Adjust the flow rate of the alloy liquid so that it does not generate gas

(5) Alloy adhering on the elimination type (mold).

Nine. Erosion

Visual inspection: There are pittings or ridges in the local position of the die casting.

The reasons for this are as follows:

(1) The position of the gate is not set properly;

(2) The cooling conditions are not good.

The solution to and prevention is:

(1) The thickness of the gate shall be appropriate;

(2) Modify the position, direction and setting method of the gate;

(3) Strengthen the cooling of the part to be washed.

X. crack

Visual inspection: The casting is placed in an alkaline solution with a dark gray at the crack. The destruction and cracking of the metal matrix are linear or wavy, and the grain is narrow and long, which has a tendency to develop under the action of external force.


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