A Guide to Close Die Forging and Open Die Forging for Structural Steel Projects

The development of modern forging techniques over the 19th and 20th century has revolutionised the production of steel. Previously, many bizarre applications were applied prior to the development of these techniques.

 

One of the most widely used techniques in modern steel production is the use of closed die forging and open die forging.

 

Depending on the type of structural steel project you are involved in, you may opt to use a mix of open and closed die products. Each process has it’s own advantages and disadvantages, economically, structurally and logistically.

 

In this article we will discuss the applications and benefits of both forging processes in developing structural steel for your project. But first, let’s talk about what Open Die Forging and Closed Die Forging are, and how they are different form each other.

 

What’s the difference between Open Die Forging and Closed Die Forging?

 

 

Open Die Forging is also commonly known as ‘free forging’. This process involves using multiple dies to encompass the metal and alter it’s size and shape .

 

Closed Die Forging, on the other hand, is also commonly known as ‘impression forging’. Uses an enclosed die impression to get the desired shape. High temperatures are used to heat the metal to facilitate this process.

 

How does the Forging process work?

 

Forging is a process associated with manufacturing that uses compressive forces to shape and mould various types of steel. The forging process can involve very high temperatures, or hot working, or could involve cold forging processes, known as cold working; sometimes, temperatures may be somewhere in between depending on the process.

 

Both Open Die Forging and Closed Die Forging involve very different processes to get the desired result. In Closed Die Forging, moulds are prepared ahead of time. This process requires very little machinery.

 

Open Die Forging on the other hand can be quite technical, particularly in the 21st century. Huge amounts of pressure are applied to forge the metal billets into the desired shapes.

 

What are Forged parts used for?

 

Depending on the forging process applied, there are different applications for both Closed Die Forged steel and Open Die Forged steel.

 

Open Die Forged steel objects, for example, require further processing as the imprecision of the hammering process leaves a rough cut of the final product. Open Die Forged steel is typically applied to large parts utilised on railways an on aircrafts. Generally these types of steel shapes may be long shafts, rollers or cylinders.

 

However, if you are looking for finer detail and more precision – for smaller parts for example – you may be looking at Closed Die Forged materials. Fittings, flanges and automotive parts are typically Closed Die Forged.

 

What are some of the pros and cons of Open Die Forging and Closed Die Forging?

 

Open Die Forging

 

Pros

 

  • Strengthened microstructure and improved resistance against fatigue;
  • Finer grain size and uninterrupted grain flow;
  • Better strength and lengthy part life;
  • Not as much waste caused by the process;
  • Cost effective.

 

Cons

 

  • Not able to form close tolerance, high precision parts;
  • Second process involving machinery to improve accuracy of desired features.

 

Closed Die Forging

 

Pros

 

  • The grain structure is aligned, increasing the strength and durability of the steel;
  • Can be cost effective for large runs;
  • The condition of the surface finish is much better;
  • Very little to no machinery required in this process;
  • Greater control over shape and dimension of product.

Cons

 

  • Can be expensive when doing short run due to expense of producing the die for moulding;
  • Dangerous work environment;
  • Setting up the machinery can be a difficult and expensive process;
  • The building hosting the machinery must meet strict standards due to the stress and strain of the forging process on the environment.

 

Summary

 

Depending on what type of your structural steel project you are involved with, it is best to consider what type of processed steel you will be using. Obviously depending on the amount, budget and specifications of the materials you need you may opt for either a Closed Die Forged product or an Open Die Forged product.

 

Although Closed Die has a smoother finish and allows you greater control over the shape and dimension of your product, it can be expensive in small runs. Typically these products are used for smaller, finer parts.

 

If your structural steel project requires larger parts, Open Die forged parts can be a cost effective option. Open Die parts tend to require more processing if you need finer and more sculpted parts.

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