The Application of Lost Foam Casting Process in the Production of Electric Power Fittings

As China's increased investment in infrastructure; electrical fittings also will expand the market demand; while the construction of power facilities is a long-term infrastructure projects; therefore electrical fittings market has been steadily. Of course, this market includes the domestic and international markets; domestic market is mainly concentrated in a few state-owned power company; overseas markets mainly in Europe and America; India and Iran; currently there are several lost foam casting plant electrical fittings in the development of products, some do and some do domestic exports; among huge source of Jiangsu Gaoyou City sincere Machinery Co., Ltd. Hydraulic Machinery and electrical fittings made all export products; below huge source of Jiangsu Machinery Co., Ltd. (hereinafter referred to as huge source machine) production electrical fittings product, for example; disappeared technics in the electrical fittings to make a presentation on the application;

Electrical fittings product line a lot, one of the most representative products is a steel cap and pull rods;

      239 steel cap white mold                    239 steel cap castings

Pictured steel cap on white mold and casting product images; steel cap the working conditions under the conditions of use and the technical requirements of the product itself, we can see that the product of the most critical dimensions of the internal dimensions because the section also requires and another part for cooperation. Lost foam process is used to produce the product in white molding above there are two options to choose from, and the overall molding slice.

1. Foam slices form

This scheme refer to separate from the middle of the symmetric part of the product type; mold can be used Half mold; diaphragm molding and then bonded into a whole; advantage of the program; molding simple, high production efficiency; white molding can be used automatic molding machine; therefore less labor; shortcomings; product's overall dimensional stability is poor; because the overall size of the final product is obtained after bonding, the bonding accuracy of the mold, operation of the workers, quality of plastic; so many factors affecting the overall product size; LFC white mold bonding glue, there are two, one for cold glue (AB glue;-component glue) one for the hot glue (hot melt); but regardless of choice of cold glue or hot glue to ensure qualified bond, bonding glue when they need to be extruded; That white mold on the adhesive after bonding glue that needs to squeeze a fillet; so as to ensure that the entire bonding surface completely bonded; once sticky junction is not completely bonded glue on the need for external processing. Because once the adhesive surface with cracks, paint will invade; after casting product is waste. The cap for steel products, after bonding glue protruding tumor is either in white or in die casting process will be very troublesome time; difficult to ensure the appearance of product quality and size; especially critical part of inner top is even more difficult to clean.

2. Molding in integral 

Molding in integral refer to white mold form overall shape through the mould, advantage; white mold without bond; product's overall good dimensional stability; reduced after the procedure; shortcomings; forming more complex; die only for manual handling; thus forming efficiency is low; labor more; through the above analysis of the two programs; huge source of the company finally adopted as a whole molding process; because we manufacture a product, you first need to consider is the quality of the product; then the product cost; so for products that do process analysis when the primary consideration is the quality of the product; must also consider overall costs; while this product is made of steel cap overall shape; increase the amount of workers only in forming a step above; but in the bond terms and the final product polished clean-up will save lost a lot of labor; speaking from the amount of labor and a slice forming essentially flat, even more is limited; while such programs both dimensional accuracy or surface quality are much better score sheet forming. While eliminating the need for the product as a whole because of this bonding procedure, thus reducing a hidden quality problems; so the final overall shape of the yield is higher than the yield of sheet forming, the cost is reduced accordingly, and the consolidated efficiency in two ways almost all the same.

Steel cap material is ductile iron products ASTM65-45-12; need hot dip galvanized surface treatment; Although this product is not working; but its intrinsic quality requirements are very high, because need for tensile steel cap assay; Once the steel cap the internal casting defects occur fracture; also need hot dip galvanized steel cap; if the product shrinkage or surface defects will appear the phenomenon of acid reflux; therefore; this product's actual requirements and processing capacity requirements are the same as leather goods , the requirement for the use of the product, in considering casting steel cap product requires attention to several issues.

1) Beads selection; in order to reduce carbon defects; selection copolymer beads; Kester chemical standard 3 # 3 # or small;

2) Appropriate adjustments ductile iron carbon equivalent.

3) Increasing pouring temperature; since the thickness of the thinnest steel cap only 4mm; very prone to cold traps for fire flow and other casting defects; therefore; requires tapping temperature of 1600 ℃; pouring temperature not lower than 1480 ℃; in such a process requires next; hand to ensure baked and pouring temperature; while the quality of the ball must be guaranteed; since high ball foundry technology in general is not very good grasp; terms in pouring time as short as possible to prevent the molten iron to cool down

4) Gating system design should take full account of slag removal system; same time to ensure a smooth filling of hot metal; otherwise thin-walled products are prone to defects in carbon residue on the folder; carbon residue on the folder defects similar to fire flow defects but not exactly the same; such surface defects do not see a lot of time out; especially when relatively large degree of vacuum can easily be concealed; such a defective product in the hot dip galvanizing acid reflux occurs when the phenomenon; if present in the thin wall position; doing tensile testing time is very easy to break;

5) Vacuum degree: filling in order to ensure a smooth; vacuum of not more than 0.04MPa; generally set at 0.03MPa. This is also the vacuum requirements of products processing.

For steel cap products, in addition to meeting the above conditions should be noted that outside; also need to pay attention to is the product fills and variations of the problem; Although this product can be plastic; however; deformation rate is very small if the casting will greatly reduce subsequent workload; therefore in terms of equipment; filling a tight and highly efficient variant of a small amount of vibration table is a must. Some factories in order to solve fills tight variant of the problem and has taken to increase the thickness of the paint used for molding sand Sarah means; surface looks to solve some problems, in fact, it brought a lot of quality problems; first; increased coating will inevitably reduce the thickness of the coating permeability and liquid adsorption; this time only to compensate by increasing the degree of vacuum; rather just be a large vacuum filling of molten iron have a huge impact; very prone to internal defects; many domestic manufacturers are chosen in such a way to make up for the lack of performance vibration table; so many manufacturers in the production of ductile iron products processing requirements when yields are low; the main problem is that many defective products after processing; second; using Orb wall sand will reduce the rigidity; especially in the production of ductile iron products Heavy; type wall directly affects the rigidity of dense tissue products; many people think; Great wall vacuum will increase the rigidity; fact, this is a misunderstanding; sand box covered plastic membrane; vacuum degree of molding sand in the plastic film is less the depth of about 200mm; 300mm vacuum of less regardless of how much the rigidity of the sand had no effect; this part of the molding sand is entirely dependent on the rigidity of vibrating table compaction performance.

Comprehensive analysis is easy to see; steel cap products, while not working, but because the product requires use of hot-dip galvanizing and particularity, in fact, lost foam process with a certain production process more difficult; especially the need to ensure that no internal steel cap allowed to have any quality defects; tensile test just because of sampling; unreasonable if the process measures can not guarantee the product's inherent quality; then the product will be there are significant quality problems; in particular, as an export product quality claims will face significant risks; from the degree of internal quality requirements in terms; steel cap product requirements actually machined products than many more stringent, because a lot of machined products are not fully processed; Moreover, as long as not inherent flaws in the machining plane; no special requirements are acceptable, while the steel cap, while not working, but the use of state of the intrinsic quality of the product they will be strictly inspected

The following is the production situation of anchor rod

           A16SJ Wotou anchor rod (ASTM 60-40-18)

Distaff Wotou product key size is also the internal dimensions; and steel caps and other products as also to be fit. Comprehensive analysis and genotyping methods, like steel cap; also uses the overall shape; another; steel shank cap products require full processing; cylindrical processing capacity of unilateral 2mm; rod 20 blind hole machining centers; product tensile testing needs to be done; distaff products and steel products in the process of considering the cap there are also differences in common;

Common ground; appearance of the product and the intrinsic quality requirements are the same; therefore have a common process parameters;

Difference; distaff than steel cap Heavy; temperature requirements so unlike steel cap as sensitive; another; considering the ingredients, it is also distinct from feeding steel cap; related distaff process consideration needs to pay attention to the following points;

1) Beads; in order to reduce carbon defects; selection copolymer beads; Kester chemical big 3 # or # 2 material; while controlling the proportion of beads is 23 grams;

2) Appropriate adjustments to the ingredients of ductile iron carbon equivalent;

3) Pouring temperature; requires tapping temperature of 1560 ℃; pouring temperature not lower than 1460 ℃; terms in pouring time as short as possible to prevent the molten iron to cool down;

4) Gating system design should take full account of slag removal system; same time to ensure a smooth filling of hot metal;

5) vacuum; filling in order to ensure a smooth; vacuum shall not exceed 0.04MPa; generally set at 0.03MPa; This is done processing products vacuum requirements.

6) Coating; requires the use of a liquid having a high adsorptive coating;

Distaff process to consider, in addition to common technical requirements; more stringent requirements on the paint; This is related to the thickness and distaff; Heavy products because of the residual carbon content to be more; This requires the paint to be the first for a time during the white mold vaporized liquid substance adsorbed to the paint; such subsequent high-temperature molten iron through again when the second vaporization; coating liquid adsorption EPC coating is an important indicator; many domestic manufacturers in the production, or are self-matching paint; regarded breathable coating on the first one; think that as long as the coating permeability high refractoriness will be able to meet the requirements, but in fact this is a misunderstanding; because the permeability of coatings depends refractory aggregate and filler particle size; That smaller mesh size bigger better ventilation; but no matter how to reduce aggregate not less than 120 mesh mesh; otherwise it will affect the quality of the casting surface; while molding sand used is quartz sand or both Pearl mesh sand are usually 30 to 70 mesh in between; although large size; but through the vaporized gas after the molding sand is very long distance; that action in a vacuum next; matter how good permeability coatings; permeability of sand is the most critical;

Thus, lost foam process in the production of ductile iron products; has high adsorptive coating liquid is necessary, at the same time; the proportion of the white mold control must be reasonable.

In LFC process to produce electrical fittings in the process is feasible from a cost is also lower than sand casting; especially a reduction in the subsequent grinding workload; either labor or environment has significantly improved. But with the disappearance of molding process to produce electrical fittings on the technology, key equipment and coatings demanding; many domestic use of large vacuum process plant is difficult to adapt; since lost foam process, especially with the production of ductile iron ball intrinsic quality requirements iron products; for the filling of hot metal, slag removal system design and coating liquid adsorption have high demands. I went to a production of steel cap LFC factory visit and study; see is because the process design, paint and other problems led to the finished product rate of less than 70%; and for products that have the appearance inspection there are significant quality problems; because for so-called qualified products; from the process point of view to analyze the quality of internal defects can not be excluded.

With the domestic market quality castings awareness; casting products for the increasingly stringent requirements; which also lost foam casting process produces a promotion; requires us to constantly improve and even lost foam casting process innovation; does not just stop After doing some processing or processing requirements are not low wear parts and gray iron products; such a process can be used instead of technology has matured; but by requiring a simple choice of product marketing. So, can solve the surface and internal quality defects lost foam casting process is a mature technology! Is a viable technology!