Sand Casting
Sand casting means the production processes that need sand as the main molding material
, it also means the casting products made by these processes.
1. Casting Process
We need make wooden, resin or metal patterns according to the drawings or samples. Then, we put patterns into the sand boxes, then put green sand or resin sand into the boxes, then make the sand become solid by pressure come from molding machines or manual methods, then take the patterns out, and so, the space taken by patterns will become hollow, then inject melted liquid iron into the hollow space, then after cooling, the hot iron water will become iron parts, the after sand blasting process, remove the sand on the surfaces, and we will get the clean cast iron parts.
2. Casting Prices
The prices of sand castings depends on rough casting cost, machining cost, surface coating cost, heat treatment, packing and delivery costs. You could find the FOB China prices on the main page of Dandong Foundry in China.
The prices of exported sand castings will be mainly affected by the exchange rate of USD to RMB and pig iron prices. Therefore, the prices are not stable.
3. Main Equipments
There are many equipments for producing sand castings.
3.1. Pattern Making
Normally, metal foundries do not make wooden and resin patterns in-house. However, some large foundries with machining capability could make the metal patterns by themselves. But as for the complex metal patterns, only the professional pattern workshops could meet the requirements.
As for wooden and resin patterns, the workshops need some manual tools and simple lathes. As for metal patterns, the workshops needs some CNC centers, numerical control milling machines, wire-electrode cuttings.
3.2. Molding Equipments
3.2.1. Manual molding, it is very traditional molding method, which is also called as hand molding. Workers use simple tools and sand boxes to complete the molding process. This method still has very wide application. Almost all metal foundries are still using this method to deal with small batch production or special sizes of castings.
3.2.2. Molding machines. These machines include mechanical molding machines or simple Leak mould machine. Leak mould machines do not have wide application since their low production rate and dimensional restriction. Molding machines are still widely used, they have their advantages, however, because of their comparatively low production rate, they have been replaced by automatic molding line step by step.
3.2.3. Automatic molding lines. These molding lines have very high production rate, so more and more iron foundries are importing them, and they are perfect for producing automotive parts.
3.3. Cleaning and Grinding Equipments
3.3.1. Sand blasting equipments are the main cleaning equipments, and there are mainly hook-type, crawler, transfer desktop shot blasting machines. After sand blasting, the castings will need workers to grind them by grinding tools to remove the burrs and sharp edges.
3.4. Furnaces
The melting furnaces main include medium frequency induction furnace and traditional cupola. More and more metal foundries have imported induction furnaces to replace cupola in order to improve the production rate and casting quality.
Machining Equipments
3.4.1. Most of metal foundries in China have their own machining equipments in-house. At least, they could complete the simple or rough machining by themselves. Some larger foundries have high precision machining tools.
4. Materials
Foundry sand is the main molding material for sand castings. The main sands include green sand, resin sand, pre-coated resin sand and water glass quartz sand.
According to the metal materials, sand casting can be divided into cast iron, cast steel, cast aluminum, cast bronze castings.
5. Casting Defects
Sand castings have many defects, such as sand holes, air holes, sand inclusion, cold shut, shrinkage, cracks etc. Less casting defects will be the main quality issue.
6. Casting Products
Sand castings could be widely used for many industrial and residential fields, mainly include stove and boiler parts, agricultural and engineering machinery parts, pump and valve bodies, pipe fittings, drainage parts etc.
7. Quality Inspection
Metal foundries normally completes the visual inspection, dimensional inspection, physical properties (hardness, tensile strength) and chemical component. As for some special tests, such as the sharp impact test, pressure test, x-ray inspection, magnaflux inspection and ultrasonic test, some professional suppliers could complete them in-house, but most of suppliers will have to entrust professional labs.
8. Casting Suppliers
In China, there are some different metal castings suppliers. Some are professional machining workshops, but they have their foundry partners. Some are professional metal foundries. Some are just trading companies, which have their own sub-suppliers.
Sand casting process has thousands of years history, and the products made by this process have taken over 80% of total castings in the world nowadays.
This article was from Dandong Foundry. For the whole article, please check Dandong Foundry Blog.
by: galen
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