The influencing factors on the quality of the casting
Production conditions and the existing problems and reflect on the social feedback allows us to continuously improve their own technology in the problem, so for the development of new casting molding method and equipment are greatly promote the development of meaning.
New modelling method and equipment for sand properties put forward higher request, sand making gas defects in casting production have been the very good treatment.
At present our country some foundry produce of stainless steel casting their bad surface gloss is very rough, scrap rate is higher, in which a large part of the reason is because of the used sand in poor quality of raw materials.
So what are the influencing factors on the quality of the casting sand?
1, sand wet strength reflects a sand mold withstand ability of various kinds of external force.
Sand mold in the process of production to stand under the mold, handling, core type, such as process, in order to avoid damage and collapsing, must have sufficient wet strength.
, in the process of casting sand mold and metal erosion and impact as well as the expansion of the graphite precipitation in force, these reasons could cause defects such as sand holes, loose, sand.
Especially the complex castings such as engine cylinder block, cylinder head, higher requirements for the wet strength of moulding sand.
In general, sand in tight at a rate of 40%, wet strength at least 0.
2, the sand compaction rate, namely the degree of wet sand.
Compressive force of moulding sand is too dry, bentonite cannot give full play to, can cause the strength of moulding sand is insufficient, also go against gas rushed modelling methods, such as compaction of sand mould and sand mould easily damaged, easy to produce stainless steel casting defects such as sand washing and sand hole;
Illiquid of moulding sand is too wet, can cause sand, sand mold is not easy to tighten evenly, and excessive moisture can cause the casting defects such as porosity, pore, choke sand inclusion.
In general, high pressure and impact modelling for modelling work position of the firm at a rate of 35% ~ 40%.
3, water content of sand casting is pinhole, blowhole defects such as a major factor.
When sand is the most suitable for dry and wet condition, the moisture content is lower, the better.
Bentonite and coal powder and sand mixing process directly affects the quality of molding sand moisture content.
Abroad with high-pressure molding, air impact modelling method in the production of automobile castings of grey cast iron and ductile iron casting factory most sand moisture content in 2.
3% ~ 3.
Bentonite have the effect of the binder in the sand, the compressive force, wet, hot, wet bonding force and reusability is the main index reflecting the quality of bentonite.
If the poor quality of bentonite used, in order to guarantee the strength of the sand mould is need to add more bentonite, sand accumulation in unbond dead clay will gradually increase.
5, sand silt content including effective and failure of the bentonite pulverized coal, by new sand, bentonite, coal and other raw materials in dust and ash, and silica sand particle breakage and into a fine powder, bentonite and coal is the main source of sand clay points.
Silt content can increase water content of sand, and permeability is decreased, stainless steel castings is easy to produce pinhole, porosity defect.
And, in the case of wet strength to achieve the same level, the toughness of the molding sand and hot wet tensile strength is reduced, prone to sand castings and sand inclusion defects.
Nanjing BoQiao Machinery Co., Ltd. thinks that that firms can avoid the artificial choice between quantitative and qualitative risk management, allowing both to play important roles in surfacing and assessing risks.
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