Global Casting News

Common defects of castings and improvement measures-blisters

2022-09-05
Defect characteristics:
Pores containing sand on the surface or inside of the casting or obviously less meat
 
Reasons for formation:
A. Low moisture content of molding sand
B. Improper design, long molding time, long-term baking and "moisture migration" cause local molding sand to have low strength and form blisters
C. Improper flow path design, hot metal scouring during pouring causes blisters
D. Poor flow path or mold draft, with pull-out cracks and sand loss
E. There is "falling sand" in the cavity, such as the molding room is worn out, the sprue cup sinks, the pressing (real) device is pressed to the gate or there is falling sand above the molding room
F. The sand core has burrs or floating sand, and it is not blown clean when the core is set.
G. The template is deformed, causing sand squeezing and falling sand
 
Improvements:
A. Polish the model and polish the flow path to reduce sand and slag holes caused by poor drafting
B. The comprehensive gating system is used in the scheme design to improve the slag retaining effect of the gating system
C. Recalculate the plan, and it is recommended to minimize the water entering the riser to facilitate the floating of sand and slag
D. Increase ante or side entry
E. If the mold parts are worn out, replace them in time
F. If the pouring time is too long or cannot be punched at the same time, recalculate the plan
G. If there is sand squeezing, when it is confirmed that there is no problem with the panel, the R angle at the clamping line of the sand squeezing position or an anti-pressure strip
H. Thinning the water inlet or blank holder to improve the slag retaining ability
I. Make a slag collection package on the plan
J. Change the position of the water inlet to avoid the parts that are easy to flush (do not put the water on the sand core blowing port)