The die coat plays an important role in aluminium die casting and it is one of the primary constituents of the die casting process.
Die coat constituents are mainly silicon(synthesise), polymers, waxes, graphite, oils, vegetable oils, anti-solder additives to enhance properties, chemicals for preservation(biocide),emulsifiers, surfactants, etc. The ratio of these constituents varies from makers to makers in their various products. The above constituents amount 20 to 30% and the rest is liquefier only.
The role of die coat
The role of die coat is to release of the casting form permanent mould made of die steel. Primarily die coat is mixed with water and the mixture is sprayed through automatic spray system commonly available with modern die casting machines. Manual method of spraying is also used by many industries. A few companies use graphite paste on die surface through manual coating (POCCHA).
The function of die coat is to form a layer on hot die surface. When water mixed die coat mist is sprayed on hot die surface, the extra water evaporates and the rest flows down from both the parts of die leaving behind invisible a few micron layer of the die surface that is film, thus doing its duty of releasing casting without galling/catching. There are means and methods to increase its effectiveness.
The next function of die coat is to provide surface cooling to die parts, thus helping the process of die casting to produce sound quality castings. It also provides cooling to plunger tip.
The other important function which die coat has to perform is to provide lubrication to the moving parts of the permanent mould/die/tool. The moving parts like slide cores, plunger and squeeze piston in squeeze and vacuum die casting advance the die casting process which provides blowhole-free /leak-proof castings.
The constant film produced by die coat mist when sprayed on die surface provides flowability to liquid aluminium. It provides the much needed support to those castings where liquid aluminium is viscous and presence of silicon is 1%.
Summing up
In my view, the die coat always plays an important role once all conditions are correct in the die casting process. For example, the conditions which play important role in the die casting process for successful die coat application and its ratio are die surfaces, metal temperature 650deg to 680deg, dietemperature 180 to 250 deg centigrade, the spray method, the spray distance, the air pressure, the workmen (if manual), the setting of spray pipes, the time of air spray, the time of spray, the die coat ratio, the churning of die coat chamber, the water quality, etc.
The die coat ratio is a very important factor in good die coat brand. Dies are of different kinds and there are different aluminium alloys. The die life also plays its role. Based on application, die condition, open close or multicore or multicore multi cavity angular pins and alloys like most common ADC 12, ADC 6 orA380, the die release agent is selected and the ratio is defined.
About SUNLUBE
The Pune-based SUNLUBE Group manufactures a variety of die lubricants, plunger lubes & graphite beads for casting industry. Their 4455 series of high performance wax-free die lubricants are some of the best available die lubes in the market and being established by well-known casting companies in India. The main features & advantages of the products are as below:
High Performance Micro Emulsion of Silicon
Suitable for the paintable components
Wax-free ,No spray head chocking
Form uniform layer on the die surface @ high temp
Compatible with Aluminium, Zinc & Magnesium Alloys
Excellent shining & better surface finish
For more details of die lubricant or any technical queries related to HPDC, write to ranjan.agkasa@gmail.com
Article by –
Ranjan Swaroop ,Director, AgKASA Industries
Ranjan Swaroop ,Director, AgKASA INDUSTRIES , a prominent name in the field of die casting. Swaroop has 20 + yrs of experience in die casting, He is a Six Sigma belt certified technocrat, Secretary -TPM and a Member of the TQM team.
He has successfully implemented AB costing and has received advanced training in squeeze & vacuum high pressure aluminium die casting in Toyota Japan, and trained in Yxlon Germany for oil cooled pistons.
He headed MNCs like Enkie, Subros, and Shriram Pistons, and managed turnaround of loss-ridden plants to profit making units.
For the last one decade, through his venture AgKASA Industries, he is into supply chain of some top automobile companies. He is also associated with the SUNLUBE Group as a technical advisor for providing guidance to clients to successfully implement die lubricants & solving any technical issues related to die casting.
