Characteristic features
The casting surface exhibits a level of roughness corresponding to the size of the sand grains.
Incidence of the defect
The defect primarily occurs near the gate and in very hot areas, and is frequently to be regarded as an early stage of penetration.
The defect is also found at positions where mould compaction is poor.
Possible causes
Clay-bonded sand
? Sand grains too coarse
? Too little lustrous carbon producer in the moulding sand
? Too few fines in the sand.
Moulding plant
? Too little compaction
? Too much adhesion of sand grains to the pattern
? Too little bonding of the sand grains in the mould surface
Gating and pouring practice
? Pouring temperature too high
? Metallostatic pressure too high
Remedies
Clay-bonded sand
? Use fine-grain sand. If necessary, refine core sand so as to adjust the fineness of the recirculating sand
? Increase production of lustrous carbon in the moulding sand. Adjust “active carbon content” to 0.35 % – 0.45 %
? Use carbon carrier that produces more lustrous carbon.
? Increase fines content. Increase coke formation in moulding sand if necessary increase return of dust in order to increase fines content.
Moulding plant
? Improve mould compaction. Increase compacting pressure. Improve sand distribution to achieve more uniform mould compaction.
? Reduce adhesion of sand grains to the pattern. Use a release agent or use it more frequently. Sufficiently heat pattern.
? Improve bonding of sand grains at the mould surface. Avoid rapid drying-out of the surface by means of better development.
Gating and pouring practice
? Reduce pouring temperature
? Improve gates. Avoid local overheating
ABOUT KEVA
Keva Casting is a professional casting company that focuses on Construction, Machinery, Automobile, Hardware, Pipeline and many other industries.
We provide top quality products with the best service based on our complete production chain including our own mold design, advanced production techniques, and full management of the supply chain. Keva Casting has two factories located in Zhucheng, China's Shandong province.
We use "shell molding", which is a new technique that has been developed in recent years.This new technique has simplified production procedures and reduced air pollution compared with traditional sand casting and investment casting. Shell making and core making are faster to ensure production in enormous quantities. The dimensions and surface finishing are satisfactory for all kinds of industrial requirements. Besides supplying our own formwork & scaffolding systems, our casting products also supply OEM services in various industries.