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A Brief Introduction of Molding Sand

When people speak of sand casting, the first thing that comes to their mind is the sand on the beach. They do not think that sand casting is one of the most popular methods which are used to produce metal parts. In order to help people get a general idea about it, the article will introduce some information about the sand casting.

Generally speaking, the sand used in foundry industry includes two kinds, namely molding sand and core sand. The molding sand is composed of 85% natural sand, 9% clay and 6% water. Sometimes, in order to improve its property, coal powder, vegetable oil and wood flour will be added into the mold sand.

Although the sand is the main material for sand casting, it is quite different from the common sand on the beach. Anyone who has built sand castles on the beach knows how fragile sand castles are. So it is impossible to use the beach sand to hold molten metal. One question that comes to the mind is what properties can help the molding sand hold molten metal. Generally speaking, the molding sand has the following features. What comes first is permeability. The ability of allowing the steam to pass through the walls of mold material is called permeability. After the high-temperature molten metal is poured into the mold, there are a lot of gases in the mold. If the gas can not be removed successfully, the casting will produce some defeats. In addition, the permeability is also influenced by the clay content, water content and graininess. The next feature is refractoriness. This is the ability of withstanding high temperatures of sand. From this point, people also can deduce that sand used for casting steel must be more refractory than one for brass or aluminum because of the greater pouring temperature. Also, a sand used to cast large heavy castings must be more refractory than one used for light thin castings of the same metal. The third feature is strength. The ability of resisting the external force is called strength. If the strength of mold sand is not high enough, the castings easily collapse. However, the strength can not be too high. Or else, the sand castings will produce some defeats due to the decrease of permeability. The fourth feature is plasticity. It refers to the ability of maintaining the shape under the effect of external force. Because the molding sand has the good plasticity, the molding operation is very convenient and the shape of mold is quite accurate.

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The problems with steel foundries in China

There are three kinds of steel foundries in China. One is the sand casting foundries, then the water glass investment steel casting workshops, and the silica sol investment steel casting workshops. We usually called the investment casting as precision casting process.

What kinds of products can these casting workshops produce?

As for the sand casting workshop, they usually make the steel castings with material of normal carbon steel, and some kinds of alloy steel. The prefer weights are from 5kg to 400kg. With normal surface and inside quality requirements, and simple machining. They usually use the green sand or CO2 gas hardening sand as the materials. The problems with these foundries are their production efficiency is low. Since they use the traditional manual molding process, their annual output is small. They can not meet the delivery time for the large orders. Second problem is their surface quality is not good. This is the common problem for all sand castings. Thirdly, they can not do the high precision machining. These workshops are usually able to make the simple machining. Of course, I do not mean all the steel foundries do not have CNC centers. Some large steel foundries have many good machines for machining.

As for the water glass investment casting workshops, they use the water glass and yellow wax as the material. We also call this casting process as lost wax casting process. This process can keep very good dimensional and surface requirements, and these workshops usually use the medium-frequency induction furnace, therefore, they can make some alloy steels. Their problems are they can not make large or heavy castings. Their prefer size is between 50mm to 300mm, and prefer weight is between 0.3kg to 5kg. This is restricted by the lost wax process.

As for the silica sol investment steel casting workshops, they use the materials of yellow wax and silica solution. So, they can keep the higher level for the surface quality and dimensional requirements. According to the experience of Mr. Galen Wang from Dandong Ruiding Foundry, the silica sol investment casting process can reach the best surface quality and dimensions. Their problems are as same as the water glass investment casting process. They have size and weight restriction. In addition, their production costs are usually three times of water glass investment castings. Therefore, unless you need absolutely high surface quality and dimensions, this process is not your best choice.

By the way, all steel foundries are not willing to make iron castings. It is because the pig iron used for making steel castings is not same as that used for making iron castings. We call this pig iron as steel pig or pig iron for steel making.

We hope this article can help the overseas buyers and purchasers to learn more about the steel foundries in China, so, they can choose the most suitable suppliers for their products.

This article was originally written by Mr. Galen Wang from Dandong Ruiding Foundry

Foundry Equipment, Sand Casting, Sand Core Making, Core Shooting Machines Shell Molding Machines Shell Moulding Machines Sand Core Making Resin Sand Core Making Iron Casting Sand Casting Green Sand Casting Foundry Core Making

A brief demonstration of backyard brass casting techniques

Aluminum Casting Foundry Crafts

In the casting method, Aluminum Casting, and other non-ferrous alloys in addition to using sand casting, but also extensive use of metal casting, centrifugal casting, low pressure casting and casting and other specialty graphite casting method.
By reference to a large number of patent documents on Aluminum Casting process technology advances to do a systematic description, through detailed investigation and authoritative technical information and related intelligence gathering, providing customers with Aluminum Casting Products core technology application, technology development, process equipment, facilities, many high-end information technology applications for enterprises to understand the various types of Aluminum Casting and the development of production technology is very useful.
Aluminum Casting Special Processing
To meet the national economy and high demand on the multi-copper, special processing techniques have been developed, mainly include: high-precision Copper Strip, ultra-thin copper foil, enhanced internal oxidation particles, a variety of metals, laser surface hardening, semi-solid forming, shaped casting, particles enhanced particle control, are highlighted as follows:
1. Precision Copper Strip
Shaped frame with high accuracy transistor type copper, phosphorus and silver generally high strength and high conductivity alloy, thin section from the side edges and composed of thick, thick edge was 1.27 mm and 0.38 mm for the Needle Valve thin side, bandwidth 68 mm, length greater than 200 meters, triple types of production methods, which pass rolling, milling chips, high-speed production of profiled forging billets, and then by high-precision rolling, the key is precision rolling technology, the need to ensure that even the thick and thin side extension coefficient equal to, or shaped with a plate can not meet user needs.
2. Within the oxygen-free copper oxide dispersion strengthened
Vacuum device required oxygen-free copper, hydrogen gas welding in the 930 ℃ without distortion, using the method of alloying is difficult to achieve, at home and abroad using the oxide particle dispersion strengthening method, commonly used oxide particles AL2O3.

In the copper alloy casting, metal casting methods to accelerate the solidification of castings to improve quality and reduce casting defects, has an important role. Metal casting can be broken grains, reduce porosity, improve the alloy’s mechanical properties and gas tightness, high lead content in lead bronze alloy of copper, metal casting, to prevent the segregation of copper components. Also, because copper alloy castings, cylinder components, and other more, so more by centrifugal casting method. In addition, large Aluminum Casting Coach Bags low pressure casting method can be used to improve the alloy density, and reduce the casting in the casting process produces inclusions. Some of the copper alloy pressure casting method can be used.

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Manufacture of Sand Castings

Manufacture of Sand Castings

Engineers have required metal castings for over 5000 years.

As the technical ability of man has progressed, so have the techniques for making a Sand Casting.

Before a foundry can start producing Sand Castings, a number of decisions has to be made regards the Sand Casting Process :

a ) Metal Type

b) Contraction Rate. Ex if the finished product is to be 48″ long, then the pattern / mould cavity, will be approx. 49″long

c) Quality of the finished product, ie manhole cover or Nuclear Submarine part

1)    A pattern is required; this can be made from a cheap timber for single items, or metal for very large quantities.

2)     Cores will be required, if the casting is to have any internal shape

3)    A Foundry Engineer will determine how to ensure the casting is sound.

4)    His final determination is called the Runner System / Method

5)     To form the bottom half of the Mould, sand is now compacted around the bottom half of the pattern.

6)    A joint line is made between the top and bottom half of the mould. 3 dowels or pins are used to ensure the 2 halves of the mould can be put together exactly in the correct position.

7)    Sand is then compacted around the top half of the pattern.

8)    Split the 2 halves of the mould

9)    Carefully take the Pattern out of the sand.

Place any Cores in the mould.

10)   The top and bottom half moulds are clamped or  weighted down

leaving a cavity inside the mould

11) Molten metal is poured down the runner until the mould is full.

12) When cool the casting can be taken out of the mould

For further information on Sand Castings Tolerances please visit jade-trading.com

Introduction for Sand Casting Process with Philip White and Jenny Dunseath in the foundry at Camberwell college of Art London. Video by Chris Follows part of the Process Arts Project – process.arts.ac.uk NOTE: Because the sand is used in a damp condition there is minimal sand dust,and this occurs at the mould face immediately arround the hot metal casting ,clearly visible when the casting is knocked out. At this stage a small watering can or spray will help to stableize this dry material.A standard dust mask could be worn.It is always worth taking sensible precautions with all processes.With sand casting on the scale immagined here keep a water spray handy and use it when cleanig away any dry material. Text Information supplied by Jenny Dunseath: Pattern Making: The Pattern is a full size model of the part that makes an impression in the sand mold, with dimensional allocation for shrinkage and finishing. If the casting is hollow, additional patterns called cores are used to create these cavities in the finished product. Patterns are usually made of wood, plastic, metal, or plaster; however, other materials or combinations of materials are used if there are additional specific properties required of the pattern. Every Pattern must have a draft angle of approximately 2° – 3° to all walls parallel to the parting direction to facilitate removing the part from the mold. Paint the surface of the Pattern with Varnish or Shellac to make it water tight and to ensure that the sand …
Video Rating: 4 / 5

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Iron casting and resin sand casting equipments development in China

China has become one of the world’s largest casting machine manufacturers. Chinese foundry machinery manufacturing industry has made great achievements in recent years. Since 1985, the original mechanical and electrical ministry began to attach great importance to the casting machinery manufacturing and put the largest special loan to support the casting machinery industry since founding of country. “large scale sand blast cleaning equipment”, “no box-type vertical injection compression molding machine”, “water glass sand reclamation equipment development” and “metal casting equipment” and other applications have been developed.

The resin sand casting equipment has met the basic needs of the domestic market, and has changed the situation of mainly relied on imports. China has been able to produce a higher level of casting automatic production line, so has partly solved the situation of importing the car engine cylinder block and cylinder head castings. China has the capability of manufacturing the high level of automatic core making machine, automatic casting cleaning machines, automatic sand processing machines, automatic die-casting machines and large-scale precision casting equipment. Overall, from 1985 to 2005, the Chinese foundry machinery manufacturing industry has been relatively rapid development, of course, we must realize that Chinese casting machinery manufacturing level has a large gap between foreign countries, and the industry growth is not stable enough, the industry market concentration is not high. These factors are restricting the development of the Chinese foundry machinery industry, so China foundry industry needs to continue its efforts in the future.

This article was written by Galen Wang from Dandong Foundry Blog.

Lost & Foundry pouring bronze medallions for the centenial trail in Spokane, Wa.

Phosphorus copper shot added to increase fluidity.

Sand casting is easy and fun, we have been teaching metal casting & sand casting to kids and adults for almost 10 years now. Check us out!

Casting the pattern made in part 15. The recessed rectangle at the top will be cut out later and is filled in to aid moulding.