The process of forging metal is critical to modern-day life. Without the ability to shape metal we wouldn’t be where we are today. From cars, trains, tanks, and rockets to garden tools, dental equipment – almost every industry relies on the ability of highly skilled professionals to forge and manipulate metal.
What is forging and how does it work?
Forging is the process of compressing, hammering, and rolling metals to manipulate their shape, structure, and use. Multiple different kinds of metals can be formed using different processes – some of which we’ll cover below.
The main types of metals that are forged include stainless steel alloy steel, carbon steel, aluminium, copper, and brass.
Evolution of forging
Wind back about 6 thousand years to when the first recorded use of forging was being used in the ancient cities of Mesopotamia. Early smiths had discovered that metals like copper, iron, and gold were more pliable under heat.
These discoveries drove what we know today as the Bronze Age, and saw the growth of agricultural tools and jewellery, and early weapons.
This set in motion a skill and an industry that today produces laser-accurate metal components for surgical and aerospace applications. Naturally, the art of forging evolved over time, with the exponential growth of the industry seen during the Industrial Revolution and the Second World War. Over the past 50 years the processes of mechanisation and hydraulics have contributed to a rigorous and highly advanced production methodology.
Hot vs Cold forging
Modern forging processes are easily differentiated by how hot the metal is when it undergoes compression and shaping.
The two broad techniques involve hot and cold forging.
- Hot forging involves heating metals, sometimes to over 1200 degrees Celsius to increase their plasticity. This is what we all imagine when we think of metal forging – the glowing hot metal being hammered into different shapes.
- Cold forging, on the other hand, involves a different process whereby the metal is placed in a die (specialised metal mould) and pressed into a second die at just below the metal’s recrystallisation temperature to form the new shape or part.
Depending on the desired finish, shape, and structure, engineers will carefully decide what kind of forging method best works for the type of metal, shape, and desired outcome.
Different types of forging
The art of forging metal has developed into a diverse and multifaceted industry with a vast array of processes that aim to deliver a range of shapes, products, and applications. Through stretching, upsetting, and compression, metals are subject to a variety of different conditions to create the finished product.
Here are the main different types of forging:
Open die Forging
Open die forging involves shaping the metal between a hammer striking down from above and a stationary anvil (the surface or block beneath the metal). The force of the hammer striking the metal deforms the metal – altering its shape and internal grain. Open die forging refers to the fact that the metal is not completely confined between the hammer and the anvil or dies. When force is applied, the metal spills or flows outward.
Closed die Forging
In contrast to open die, closed die forging or impression-die operates on the same principle except the metal is restricted by the dies (or mould) on all sides. This is then placed on the anvil and hammered until the metal fills out the die mould. This technique allows the forger to create large shapes that require little finishing.
This slower and more controlled method of forging uses a ram to assert continuous pressure on the metal instead of sharp hammer impacts. This technique allows the forger to shape metal in a controlled and uniform process that delivers a more thorough deformation and produces little waste (known as flash) compared to other methods.
Roll forging can be likened to a home pasta maker. Instead of hammering your pasta dough into shape, you carefully guide it through the rollers to create thin strands – exactly the shape you intended. Roll forging passes a heated bar of metal through cylindrical rolls that indent the metal as it passes through – eventually creating the desired shape and structure.
Isothermal forging involves both the metal and the dies being heated to the same temperature. Through a process of adjusting temperatures externally (adiabatic heating) the mould and metal within are manipulated into the desired shape through internal manipulation instead of external forces acting upon it. This system is extremely efficient as it involves minimal heat loss and can be carried out by smaller machines.
Precision forging is a highly accurate process that involves minimal flash and delivers a near-finished or net product that requires little or no machining. This process also involves highly accurate dies and moulds however expect higher costs due to the ongoing maintenance to keep the moulds in peak condition.
As an industry, forging is responsible for the infrastructure that makes our modern society possible. From roads, bridges, buildings, and agricultural systems, forging has almost infinite applications that continue to grow in size, complexity, and sustainability.
But forging isn’t just about creating bridges and cars. It’s also about the creation of finely crafted goods, laser-accurate computer parts, and surgical tools that benefit society as a whole.
Choose the right forging manufacturer
When choosing a forging manufacturer, it’s important to scope out a variety of firms to find the right one for your needs. With different forgings specialising in different techniques, you should consider how precise, durable, and sustainable you want your product. Choose a firm with a large production capacity to ensure your project is delivered accurately and on schedule.