Steel is the most versatile material in metal casting. Steel can be easily welded and processed and plays a vital role in maintaining the high standard of living enjoyed by the industrialized nations of the world.
The versatility of steel can be easily recognized by its applications which range from high strength structural applications to excellent corrosion resistance in aggressive fluids. The differences between steel casting and steel forging are principally in the method of production. In the case of steel forging, slabs and ingots are mechanically worked to produce required product forms. However, steel castings are produced in the final product form without any intermediate mechanical working. Steel castings are near net shape products.
Although cast steel accounts for only 10% of the total foundry industry sales, steel castings are used for vitally important components in the mining, railroad, truck, construction, military, and oiland gas industries. Steel castings are specified for applications which require weldability, abrasion resistance, high strength, low and high temperature service and corrosion resistance.
There are approximately 300 steel foundries in China, especially in Ningbo. Due to the diversity of market requirements such as size, tolerances, chemistry, volume, etc., a single foundry cannot serve all of the market and each company will tend to specialize in a portion of them total market.
Steel Investment Casting Process
A steel casting is completed by pouring molten steel into a mold cavity. The liquid steel cools and solidifies in the mold cavity and is then removed for cleaning. Heat treating may be required to meet desired properties. This process provides the near net shape and mechanical properties required to meet the product’s specification. Referring to our investment casting process for detailed steps.
Heat Treating & Machining
When a steel casting has cooled, it is shaken out of the mold. Before it can be shipped, it must be finished or cleaned. The first step is an abrasive blast which cleans the surface of all residue of the mold. Then the extraneous metal of the gating system and fins are removed by torch cutting, sawing or grinding. Welding of discontinuities is a common practice in the steel casting industry.
Heat treatment processes may be used to enhance the properties. The scale formed on casting surfaces during heat treatment is removed by abrasive blasting.
Steel castings can be straightened by pressing if warpage occurs during processing. This operation ensures dimensional accuracy of the finished part.
Pre-machining or rough machining has become very common in steel foundries. When the customer requires very precise location of finish stock or reduced finish stock the foundry can perform a rough machining operation to provide the desired characteristics. Our investment casting foundry can also supply parts in the finish machined condition.
As mentioned earlier, pattern quality, mold material, pre-machining, straightening, etc., can all affect tolerances. The ability to control the casting process is of extreme importance to today’s steel casting foundry, and the supplier of choice can document his programs for the buyer.
Why Use a Steel Casting?
Many of the alloys required for severe applications cannot be forged and must be cast (casting vs forging).
All carbon and low alloy steels are readily weldable. Higher alloy grades such as manganese and stainless steels are routinely welded using appropriate techniques.
Steel castings are readily heat treated by normalizing, annealing, quench and tempering, localized or differential hardening, etc., depending on the mechanical properties required.
The corrosion resistance of high alloy cast steels is comparable to wrought 300 series material but the CF grades have a slightly different composition and contain ferrite for improved weldability. The high alloy and nickel-base alloy castings are used in chemical processing plants and corrosive environments.
Wear Resistance of cast steels is also good. It varies from a relatively soft medium carbon steel of .25 percent carbon to the extremely hard “work-hardening” manganese grades and the high chrome irons. Cast steels exhibit superior toughness and impact resistance compared to other materials.
Heat resistant alloys are used at temperatures in excess of 1200 °F (649 °C). These materials are usually alloys of iron, chromium, and nickel.
Weight and Size Range . Steel castings are produced from ounces to over 100 tons and in quantities from one to thousands per order. Each casting will exhibit the chemistry and mechanical properties specified by the buyer.
Steel castings can be joined to other product forms (wrought, forged, etc.) to produce cost-effective fabrications.
Who Uses Steel Castings?
Steel casting covers the industries who are major users of steel castings and the applications that require the unique properties of cast steel. The generic term “steel” covers a wide range of grades of materials, however, for simplicity two alloy groups are normally considered: Carbon and Low Alloy (C&LA) and High Alloy. High Alloy grades include stainless steels and nickel-base alloys. Austenitic Manganese steels and all other non-stainless steels are usually included in the C&LA group. The total steel casting production in China excluding high chromium irons is dominated by the C&LA grades.
Typical users of steel castings are:
Railroad industry which uses 50% of the total production of steel railway castings. These parts are used in severe applications such as couplers, draft gears, side frames, bolsters, and wheels.
Construction machinery manufacturers use about 15% of the steel castings produced each year. The applications here are as varied as the equipment produced. Parts range from bucket teeth for excavators to transmission housings on large earth-moving machinery.
Valves and fittings of cast steel account for about 5% of production and are used for the drilling, recovery, transportation, and refining of natural gas and crude oil both on land and offshore. Theseparts vary in size from a few pounds to many tons. Applications are very severe requiring performance in corrosive liquids at both subzero and elevated temperatures. Operating pressures can reach many thousands of p.s.i. in valves and blowout preventers.
Heavy trucks—both on and off-highway—use about 5% of industry production. Some applications include: axle housings, suspension brackets, wheels, brake parts, axle spindles, differential housings, and fifth wheels.
Mining industry makes extensive use of steel castings for their extreme requirements of toughness and abrasion resistance both for ore recovery equipment and crushing mills. Both high manganese and other alloy steels are widely used, and these materials can only be produced as castings.
Numerous other industries use steel castings. These range from food processing and electronics to oil and gas, defense and pulp and paper industries. In fact, castings touch every aspect of our lives.
How to Purchase Steel Castings?
When a steel casting is required to perform a specific engineering function and the specifications have been determined, the next step is to select a supplier for that part. Several potential sources should be visited by the quality, engineering, and purchasing departments to audit each facility to determine several qualified sources. A detailed inquiry can be sent to steel casting manufacturer.
This inquiry should include current engineering drawings showing:
- Machined surfaces
- Material specification (preferably a standard specifying body like ASTM)
Special requirements such as:
- Dimensional tolerances
- Soundness (radiography, N.D.T.)
- Special inspection and tests certification
In addition, the inquiry should show:
- Quantity and delivery required
- Weight (if available)
- Painting, if required
- Name and phone number of person to contact regarding questionson the inquiry
- Shipping destination
- Machining, if required
Treat your foundry supplier as a valued source, not only for castings, but also for advice on:
- Molding methods
- Pattern options
- Metal specifications
- Design assistance for lowest cost
Pls contact us once you are looking for a reliable steel casting supplier in China. We will try our best to send you our most reasonable prices.