Sanzhuji makes a simple analysis of the main casting defects arising in the process of large art casting of copper and copper alloy resin sand process, and proposes practical process solutions.
Copper and copper alloy large art casting resin sand casting process for large castings, generally using segmented block modeling, sand box modeling or steel pipe welding frame modeling, copper alloy formula selected from the excellent casting performance of ASTM B584 standard C90300 tin bronze (tin 7.5% to 9.0%, zinc 3.5% to 5.0%, copper 86.0% to 89.0%). Casting defects arising from the casting process mainly include: expansion box, slag, shrinkage, under-pouring, etc. Sanzhuji is now combined with specific production practices to analyze the causes of casting defects and how to prevent or reduce.
In the specific production, the specific performance of the molding furan resin: free formaldehyde 0.29%, free acid is 1.94%; coating performance: density of 1.255 g/cm3, viscosity of 15.7 s, gas emission of 17.9 mL/g. Modeling sand is natural quartz scrubbing sand, particle size 97.2% concentrated in 50/100 mesh, mud content of 0.28%, SiO2 The amount of resin added is 1.5% of the sand weight, and the amount of curing agent added is 40%-70% of the resin, and the sand is fully mixed by S25 double-arm resin sand mixer.
1.Expansion box
1.1 Performance characteristics：
The overall thickening or partial thickening of the casting, resulting in thin and thick uneven castings, affecting the overall mechanical properties, while consuming the copper alloy, increasing the cost. When the situation is serious, it can cause the casting scrap.
1.2 Causes：
The molding is not in place; the process hole is not reasonable; the reinforcement screw is not tightened; the silica sand for molding is recycled and reused, the dust content is too high, resulting in insufficient strength of the sand; the sand is deformed; the pouring temperature is too high, the pouring speed is too fast, etc.
1.3 Solution：
When the sand type is closed, the box should be dropped smoothly at all four corners to close, and check whether it is in place, and adjust the deformed or unfitted blocks; open the process holes scientifically according to the different shapes, and check the reinforcement screws repeatedly before pouring, and make sure to tighten them solid; detect the powder content of silica sand, and make sure to replace the new sand or mix more new sand into the old sand in time; measure the temperature of copper liquid strictly before pouring, and make sure that according to the size and complexity of the type block Choose a reasonable pouring temperature to ensure that the copper liquid enters the cavity evenly and smoothly.
2.Slagging, shrinkage and loosening
2.1 Performance characteristics：
The casting surface has a very obvious oxide layer, there are many small scattered and irregularly shaped holes. These casting defects seriously affect the surface aesthetics of the casting, while affecting the welding properties and mechanical properties. But only effective control of shrinkage and can not be completely solved.
2.2 Causes：
Copper alloy smelting without stirring slag or slagging is not clean, the melting process of large air absorption, pouring slag blocking link is not done, pouring temperature, etc..
2.3 Solution：
Copper alloy liquid should be fully stirred before the furnace, temperature measurement before pouring, secondary slag picking, careful slag blocking during pouring, smooth pouring. The casting slag and shrinkage are obviously reduced and the casting quality is improved.
3.Insufficient watering
3.1 Performance characteristics：
Casting bottom with insufficient pouring, casting middle with flower block, or both sides of the pouring insufficient.
3.2 Causes：
Low pouring temperature, slow pouring speed, sand venting hole is small, easy to produce air-holding, small parts of the block breakage, etc.
3.3 Solution：
Resin sand curing agent is added strictly in accordance with the ratio required in winter and summer, and the strength of the sand type must be ensured; check carefully whether the sand block is broken and fallen off before closing, and whether the closing is in place; ignite and induce gas before pouring; place the block flat or vertical before pouring; strictly control the pouring temperature and pouring speed and other process measures.
Qingdao Sanzhuji Equipment Manufacturing Co., Ltd. specializes in the production of Green Sand Molding Line,Self-hardening sand molding line,foundry machines,Sand molding machine,Sand casting equipment,sand mixer,GS high efficiency rotary mixer,Resin sand mixer,no-bake resin sand mixer,Jolt squeeze molding machine/Jolt-squeezing moulding machines,Multi- Piston Moulding Machine/Hydraulic multi-piston moulding machine,sand casting molding machine,sand reclamation equipment，foundry molding machine,flaskless moulding machine,shot blasting machine,dust collector,according to the amount of old sand recovered Carry out plan customization, and provide sand reclamation equipment installation, commissioning, and training. Welcome guests to visit the factory.
