Common problems of die casting die


Common problem

It is very important to control the surface temperature of die casting mold for producing high quality die casting. Uneven or inappropriate die casting mold temperature will also lead to casting size instability, casting deformation in the production process, resulting in thermal pressure, sticky mold, surface depression, shrinkage holes and hot bubbles and other defects. When the mold temperature difference is large, the variables in the production cycle, such as filling time, cooling time and spraying time, will have different degrees of influence.

1). Cold lines:
Reason: the temperature of the front of the melting soup is too low, and there are traces of overlap
Improvement methods:

1.Check whether the wall thickness is too thin (design or manufacture). Thin areas should be filled directly

2.Check whether the shape is not easy to fill; Too far away, closed areas (such as fin, bulge), blocked areas, too small rounded corners are not easy to fill. And notice if there are rib spots or cold spots

3.Shortening the filling time, shortening the method of filling time

4.Change of filling pattern

5.Methods to increase mold temperature

6.Raise the temperature of the soup

7.Check alloy composition

8.Increasing the escape route might help

9.The vacuum device may be useful

2). Crack:
The reason:

1.Shrinkage stress

2.Split by force upon ejection or completion of edge

Ways to improve:

1.More rounded corners

2.Check for hot spots

3.Pressurization time change (cold chamber machine)

4.Increase or shorten the mold closing time

5.Increase the drawing Angle

6.Add the ejector pin

7.Check whether the mold is misaligned or deformed

8.Check alloy composition

3). Porosity:
The reason:

1.Air mingled in the molten soup

2.Source of gas: melting, in the feed tube, in the mold, release agent

Improvement methods:

1.Moderately slow speed

2.Check whether the runner turns smoothly and the cross-sectional area is decreasing

3.Check that THE ESCAPE AREA IS large enough, that it IS blocked, and that it is LOCATED at the last filling place

4.Check that the release agent is sprayed too much and the mold temperature is too low

5.Use the vacuum

4). Cavitation erosion:

Cause: Due to the sudden decrease in pressure, the gas in the molten soup expands suddenly, impinges on the mold and causes mold damage
Improvement methods:
The cross-sectional area of the flow channel should not change rapidly

5). Shrinkage cavity:

Reason: When the metal is solidified from liquid to solid, the space occupied by the metal becomes smaller. If there is no metal replenishment, shrinkage holes will be formed, which usually occur at slower solidification

Improvement methods:

1.Increase the pressure

2.Change mold temperature. Local cooling, spray release agent, reduce mold temperature,. Sometimes the position of the shrinkage cavity is changed rather than eliminated

6). Peeling:
The reason:

1.The filling pattern is not good, resulting in overlapping of molten soup

2.Mold deformation, resulting in melting soup overlap

3.Inclusion oxide layer

Improvement methods:

1.Switch to high speed early

2.Shorten filling time

3.Change filling mode, gate position, gate speed

4.Check whether the mold is strong enough

5.Check that the pin mold is in good condition

6.Check for inclusion of oxide layer

7). Bellows:
Reason: THE FIRST LAYER OF MOLTEN SOUP ON THE SURFACE OF THE rapid cooling, the second layer of MOLTEN soup flow failed to melt the first layer, but there is enough fusion, resulting in different tissues

Improvement methods:

1.Improved filling pattern

2.Shorten filling time

8). Holes produced by poor flow:
Cause: The molten soup flows too slowly, or is too cold, or the filling pattern is poor, so there are holes in the solidified metal joints

Improvement methods:

1.With the improvement of cold grain method

2.Check whether the temperature of the soup is stable

3.Check whether the mold temperature is stable

9). Holes in the parting surface:
Cause: May be shrinkage or stoma

Improvement methods:

1.If shrinkage hole, reduce the thickness of the gate or overflow well inlet

2.Cooling gate

3.If the stoma, pay attention to the problem of exhaust or gas

10). Flash:
The reason:

1.Insufficient clamping force

2.The mold does not fit well

3.Lack of mold strength

4.The temperature of the soup is too high

11). Shrinkage in:
Cause: Shrinkage hole occurs under the surface of the pressing part

Improvement methods:

1.The same way to improve the shrinkage hole

2.Local cooling

3.Heat the other side

12). Carbon deposition:
Cause: Release agent or other impurities accumulate on the mold.

Improvement methods:

1.Reduce the amount of releasing agent

2.Higher mold temperatures

3.Select the appropriate release agent

4.Dilute the release agent with soft water

13). Bubble:
Cause: Gas is trapped under the surface of the casting

Ways to improve:

1.Reduce air entrainment (same air hole)

2.Cooling or low mold temperature protection

14). Sticky mode:
The reason:

1.Zinc is deposited on the surface of the die

2.The molten soup impinges the mold and causes the mold surface damage

Improvement methods:

1.Reduce mold temperature

2.Reduce the roughness of the scratch surface

3.Increase the drawing Angle


5.Change of filling pattern

6.Reduce gate speed