Tel.

+86 311 8926 0859

Fax

+86 311 8502 8537

Home > News > News

Difference Between Cast Steel Valves and Forged Steel Valves

Dec. 02, 2021

Valves are an integral part of any industrial unit or system. Industrial valves are used to regulate the flow of media through a pipeline, isolate certain areas of a pipeline, check the system integrity of a unit, etc. This is why industrial valves need to be of the highest quality, leak-proof, efficient and durable.

 

Casting

Casting is a method of producing various object by pouring liquid (molted) metal (steel), or another liquid or suspension capable of solidifying, into the mold of the required shape. The casting method is chosen primarily for products of complicated shapes, which cannot be produced by a different method or are made in complicated or expensive way (e.g., by machining or welding). After pouring the steel into the mold, the liquid steel is in immediate contact with a cold wall, which cause decreasing the temperature of the steel and its crystallization. The casting temperature, for example of carbon steel, is around 1 450 °C.

 

Cast steels have a chemical composition like forge steels but compared to forge steels they have worse mechanical properties which can be improved by their heat treatment. For cast steels the beneficial effect of forging (compaction of the material) is not possible. The advantage is the possibility of casting complicated shapes, which cannot be produced by forging and the material savings due to this.

 

Valve Body


Forging

Forging is a nondestructive technological process of material processing, in which the shape and mechanical properties of this material change. While forging metals, it is necessary to exceed the elasticity limit but not to exceed the strength limit. Therefore, ductile materials are suitable for forging, i.e., materials that have those two limits sufficiently far apart. Forging methods includes rolling (sheet metal), forging, drawing, extrusion.

During the forging, the grains are stretched and subsequently softened, giving the steel a homogeneous structure and better mechanical properties. From the above mentioned is clear that the forge materials have better mechanical properties and inner structure than cast materials. Forging is divided into cold and hot forging, which is carried out at temperature up to 1 200 °C.

 

Pros and Cons of Forged Valves

There are many reasons why you may want a forged valve for your application instead of a cast valve. Forged valves do tend to be better for high temperature and high pressure applications. These types of valves are less prone to thermal fatigue because the walls are thinner compared to cast alternatives. Also, forged options have a higher mass, making them mechanically stronger. 

However, there are a few reasons why a forged valve may not be best for your application. First, the forging process does create limitations for valve size and shape. Forging generally works better for smaller valves and components. In addition, not every metal is suitable for forging, which limits your options for valve material. 

 

Pros and Cons of Cast Valves

Cast valves are a great option where you need quick turnaround and low cost valves, as they require less labor to produce. Also, the casting process allows for more complex shapes and valve manufacturing. You also have greater flexibility in material choice, as many types of metals are suitable for casting. 

While cast valves are quite strong and durable when you choose a high quality manufacturer, there are still some restrictions. For example, the solidification process can create small impurities in the metal. They also are less resistant to high temperatures and pressures compared to a forged ball valve. 

 

In comparison to castings, the structure of forgings ensures wall thickness and dimensional tolerances are uniform. High impact closed die press forces and a segregation free billet guarantees superior strength, uniformity, integrity and density. Casting issues include inter granular corrosion, stress weakness, fatigue, cracks, porosity, sand pockets, weld repairs, scars, etc. Another benefit of forgings is the directional flow lines structure. 


Delete
  • wechat
Chatting