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The basic knowledge of aluminum casting ingots(F)
Dec 01, 2017


8

Common problems of aluminum alloy

 

1. Ingot surface is not flat, there are more honeycomb holes, cracks

 

A. When the silicon content of the alloy reaches about 12%, the temperature of the alloy crystallization becomes narrower, shrinkage and shrinkage occur at the top of the ingot during solidification, which is caused by the nature of the alloy, and is eutectic silicon aluminum bright Characteristics. ADC-12 alloy in particular will produce this phenomenon. Crack phenomenon does not occur when the silicon content of 10.5% or less.

B. The jitter (vibration) of the conveyor belt accelerates the solidification of the alloy liquid, resulting in the increase of the shrinkage cavity and the shrinkage depth, resulting in a honeycomb-like hole, which is caused by external factors and has no influence on the intrinsic quality.

C. And raw and cooked raw materials ratio is closely related.

 

2. Molten thick liquidity is poor, difficult to die-casting, if it is heated, easy to over-fire

 

Any metal melted into liquid, will produce a pot substrate (sediment), high-grade and low-grade metal, but the difference between the number of pot substrate only.This is closely related to the purity of raw materials.After dubbed the alloy, aluminum Silicon alloy to be added about 10% of silicon raw silicon metal on the calcium (Ca), iron (Fe) and other impurities, and an increase of calcium oxide, ferrous oxide and other impurities. The pot substrate is mainly metal compounds and non Impurities attached to metal compounds, increasing the temperature does not work, by spectrophotometry found that the ingredients go completely like, can no longer be used for casting. Thus, the operation must be noted:

 

A. Aluminum ingot melting soup, the sinking material must be isolated and separated, can not be mixed into the ingot soup;

B. users in the die-casting production process, each crucible aluminum soup to be poured into a certain amount of residue when cleaning the bottom sediment and clean up the crucible, not allowed in the pouring process continue to join the risers, waste castings, fly Side aluminum scrap, so that the bottom of the pot sediment gradually piled more, and finally the formation of a pot of aluminum sticky paste was not only lost mobility, but also very difficult to clean the pan. Many domestic users often happen.

 

3. Sputter Shen sediment and more, was thick paste, if the study of its light, Fe, Mn often more than 2%

 

See the answer to the above question: The molten sediment is too much sediment, precipitation material (pot substrate) by the light, the alloy composition has been chaos, manganese (Mn) and iron (Fe) has been formed (Fe.Mn) AL6 compound. The substrate has been deposited repeatedly, requiring users to correct the smelting method in time, according to the question 2 the correct process operation.

 

4. Easy sticky mold, poor mold release

 

A. The quality of the release agent used is not good, such as water agent graphite mold release agent, leading to the casting can not slide smoothly from the cavity

B. Alloy content of impurities exceeded

C. mold stripping slope is too small, poor mold release;

D. too old mold cracks, resulting in sticky mold

E. alloy iron content is too low, lower than the standard range of die-casting process requirements, can also cause sticky mold

 

5. Aluminum ingot cross-section of slag, molten soup continuous golden yellow scum, black suspended particles scum

 

Aluminum alloy smelting process, commonly used in Cleaners, modifiers, such as magnesium addition to the flux, the raw materials of these additives are mainly composed of fluoride, nitrate, chloride and other components of these halogen alkali compounds volatilize will cause the golden yellow Scum; black suspended particles generated scum, mainly because the melting point of silicon as high as 1,412 degrees Celsius, in the aluminum melting process, if not according to the rules, the silicon will melt into solid solution, nascent silicon in aluminum soup Floating in the liquid surface was black suspension, so the slag removal process must not be careless, we must operate according to the process and practical use of carbonate, sulfate, nitrate and other dubbed flux, the chemical reaction products easy to form and Dry residue of liquid aluminum separation.

 

6. Smelting by strict degassing step, still can not get rid of gas

 

Aluminum degassing process has become more and more perfect, there are inert gas degassing method and solid flux degassing method. Gas degassing chlorine, argon, nitrogen, and three gas degassing; solid flux degassing agent hexachloroethane , Carbon tetrachloride, sodium nitrate, non-toxic gas degassing agent, etc. As long as the operation is reasonable, can remove the liquid gas (H2) .First degassing flux itself is not gas, the gas is Refers to the hydrogen (H2) from the water (H2O), so the degassing agent itself is very strict on the gas content, dehydration generated when processing sometimes degassing operation, still can not get rid of gas, which is often Degassing agent caused by poor quality, such as degassing agent in the water content is too high, degassing agent placed too long time, the pan-tide is not fresh, etc. To observe the other side of the concrete manufacturers to use the specific, the process and collaborative solution.

 

7. Gravity casting, the piston near the riser at the finished product there are a large number of pores

 

This is the casting process, caused by improper mold design: piston casting process has long formed a complete set of design (JINGREN method), gooseneck gate system.According to the piston diameter size, wall thickness, according to one or both sides, a single Or two risers (side riser.) Some production plants to save liquid aluminum, only the design of small gates and small risers, resulting in riser is too small, poor feeding, resulting in porosity.

 

8. Die-casting after the finished product riser peel, riser Department "eat" over the finished product, resulting in increased non-performing rate

 

A. mainly unreasonable die-casting mold design and the gate size is too thick will cause "with meat" phenomenon

B. The location of the gate in the casting thin wall will also result in clean-up "with meat" phenomenon

C. cake (*) is too thin, there are shrinkage at the fracture, inclusions.

<Die-casting casting system points within the gate, overflow tank, cake (block), is not set "riser", so that "riser" is wrong, it should be called blocks (cake)>

 

 

9. Open mold cracking mouth Department

 

A. Mold design, making unreasonable, when the mandrel mold length is not coordinated (not synchronized)

B. Top position design is not reasonable

C. Raw materials more brittle, toughness is not enough. Sampling analysis, that is clues, depends on the specific castings in kind to clear what is the cause

 

10. Castings in the post-processing polishing, finishing, drilling brittle, easy to break castings

 

A. Al-Si alloy high silicon content, crisp material, easy to break

B. Aluminum alloy liquid insulation and shelf time is too long or overheating alloy liquid can also cause brittle, cracked

 

11. The confluence of castings can not be fully integrated and obvious marks left

 

A. alloy liquid temperature is low or mold temperature is low, fluidity of the alloy liquid is poor, will cause this defect, the main flow is not welded two shares

B. filling speed is low

C. Mold design is not reasonable, the distribution of overflow trough position

D. low specific pressure; each cast structure of different sizes, according to the physical design of the correct casting process

 

12. Die casting products can not be formed

 

The entire die-casting technology has not mastered, it is recommended that the other die-casting plant to strengthen technical force.

 

13. Casting irregular black stripes on the surface, water ripples

 

A. Too much paint (using water-based graphite coating)

B. mold temperature is too low (less than 180 degrees Celsius will have to produce flow marks)

C. Filling speed is too high to produce water ripples

 

14. Dark cast black hair surface, there is oxidation, and sometimes white hair

 

A. improper storage of castings, open storage, rain exposure; or stacked castings near the plating, heat treatment workshop

B. working environment is too poor, there is moisture in the air, acid, alkali overweight, can lead to aluminum casting surface oxidation

C. Release agent has deteriorated

 

15 casting surface "missing meat" or "rough surface"

 

Recessed surface of the casting causes Academic terms "depression", also known as "shrink concave", "hold your breath," causes

A. The overflow tank is too small, too thick or not thick enough to set up an overflow tank

B. mold temperature is too high

C. The pressure is too low


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