Forging is the process of deforming metal into a predetermined shape using certain tools and equipment—deformation is accomplished using hot, cold, or even warm forging processes. Ultimately, the manufacturer will look at a number of criteria before choosing which type of forging is best for a particular application. When a piece of metal is hot forged it must be heated significantly. The average forging temperature necessary for hot forging of different metals is:.
During hot forging, the temperature reaches above the recrystallization point of the metal.
This kind of extreme heat is necessary in avoiding strain hardening of the metal during deformation. In order to prevent the oxidation of certain metals, like super alloys, a type of hot forging called isothermal forging is a good choice. In isothermal forging, the metal deformation occurs within a highly controlled atmosphere, similar to that of a vacuum. Hot forging is also recommended for the deformation of metal that features a high formability ratio.
Other considerations for hot forging include:. Cold forging deforms metal while it is below its recrystallization point. Cold forging is generally preferred when the metal is already a soft metal, like aluminum.
This process is usually less expensive than hot forging and the end product requires little, if any, finishing work. Sometimes, when aluminum is cold forged into a desired shape, it is heat treated to strengthen the piece. This is called "tempering. The most common metals in cold forging applications are usually standard or carbon alloy steels. One of the most common types of cold forging is a process called impression-die forging, where the metal is placed into a die that is attached to an anvil.
The metal is then hit by a descending hammer and forced into the die. Depending on the product, the hammer may actually be dropped on the metal numerous times in a very rapid sequence. Manufacturers may choose cold forging over hot forging for a number of reasons—since cold forged parts require very little or no finishing work, that step of the fabrication process is often dispensable, which saves money.
Cold forging is also less susceptible to contamination problems, and the final component features a better overall surface finish. Other benefits of cold forging include:. Stay up to date on industry news and trends, product announcements and the latest innovations. Guides Share:. Waterjet Cutting.Forging is a manufacturing process, which shapes a workpiece by applying compressive forces on it.
The most common configurations use hammers or presses to squeeze and deform the material into high strength parts. It is essential to note that the forging manufacturing process is completely different from the casting one, where the molten material is poured into a mold. Another significant difference to the other manufacturing methods as casting and machining is that forging improves the mechanical properties of the material by refining its grain structure and making it tougher and stronger.
The cold forging manufacturing process is performed at room temperature. The workpiece is squeezed between two dies until it has assumed their shape. To deliver a finished, ready to fit component, the technique includes rolling, drawing, pressing, spinning, extruding and heading.
Manufacturers may prefer cold over hot forging process; since cold forged parts require very little or no finishing work, which saves cost. The second significant advantage is the material savings achieved through precision shapes. The economic advantages combined with high production rates and long die life are more than enough to convince many manufacturers that cold forging is the best option for them.
A second more significant disadvantage is that cold forged metals are less ductile, which makes them inappropriate for certain configurations. Also, because of the grain structure that gives the material its strength, residual stress may occur. This temperature is necessary in order to avoid strain hardening of the metal during deformation. Hot forged components possess increased ductility which makes them desirable for many configurations.
Also, as a technique hot forging is more flexible than cold forging, since customized parts can be manufactured. Less precise dimensional tolerance is a possible disadvantage of hot forged components compared to the cold forged ones.
Cold Forging vs. Hot Forging – Considerations, Benefits and Drawbacks
The cooling process should be also performed under special conditions; otherwise there is a risk of warping. Also, the grain structure of forged metals may vary and there is always a possibility of reactions between the atmosphere and the workpiece. The main difference between hot and cold forging may be summarized as follows: The cold forging manufacturing process increases the strength of a metal through strain hardening at a room temperature.
On the contrary the hot forging manufacturing process keeps materials from strain hardening at high temperature, which results in optimum yield strength, low hardness and high ductility. Finally, a manufacturer would choose one process over the other because of economic and not quality reasons.
Setforge provides cold and hot forging, both performed in excellent conditions with state-of-the-art machinery for perfect results.
We work close with our customers to understand their specific needs and find the best possible solution. If you need to know more about a related topic or require our expertise to complete a project, we will be pleased to help you! We share our expert insight to help you take informed decisions. Hot Forging — Considerations, Benefits and Drawbacks.
Cold Forging vs. Cold Forging Cold Forging Manufacturing Process The cold forging manufacturing process is performed at room temperature. Cold Forging Benefits Manufacturers may prefer cold over hot forging process; since cold forged parts require very little or no finishing work, which saves cost.
Hot Forging Advantages Hot forged components possess increased ductility which makes them desirable for many configurations. Hot Forging Disadvantages Less precise dimensional tolerance is a possible disadvantage of hot forged components compared to the cold forged ones.
Hot Forging vs.Forging is a manufacturing process involving the shaping of metal using localized compressive forces. The blows are delivered with a hammer often a power hammer or a die. Forging is often classified according to the temperature at which it is performed: cold forging a type of cold workingwarm forging, or hot forging a type of hot working.
For the latter two, the metal is heatedusually in a forge. Forged parts can range in weight from less than a kilogram to hundreds of metric tons. Since the Industrial Revolutionforged parts are widely used in mechanisms and machines wherever a component requires high strength ; such forgings usually require further processing such as machining to achieve a finished part.Fully automatic gear cold extrusion cold forging hydraulic press production line
Today, forging is a major worldwide industry. Forging is one of the oldest known metalworking processes.
The smithy or forge has evolved over centuries to become a facility with engineered processes, production equipment, tooling, raw materials and products to meet the demands of modern industry. In modern times, industrial forging is done either with presses or with hammers powered by compressed air, electricity, hydraulics or steam. These hammers may have reciprocating weights in the thousands of pounds. Some steam hammers remain in use, but they became obsolete with the availability of the other, more convenient, power sources.
Forging can produce a piece that is stronger than an equivalent cast or machined part. As the metal is shaped during the forging process, its internal grain texture deforms to follow the general shape of the part.
Hot Forging Vs. Cold Forging
As a result, the texture variation is continuous throughout the part, giving rise to a piece with improved strength characteristics. Considering all the costs that are incurred in a product's life cycle from procurement to lead time to rework, and factoring in the costs of scrap, and downtime and other quality considerations, the long-term benefits of forgings can outweigh the short-term cost savings that castings or fabrications might offer.
Some metals may be forged cold, but iron and steel are almost always hot forged. Hot forging prevents the work hardening that would result from cold formingwhich would increase the difficulty of performing secondary machining operations on the piece. Also, while work hardening may be desirable in some circumstances, other methods of hardening the piece, such as heat treatingare generally more economical and more controllable.
Alloys that are amenable to precipitation hardeningsuch as most aluminium alloys and titaniumcan be hot forged, followed by hardening.
Production forging involves significant capital expenditure for machinery, tooling, facilities and personnel. In the case of hot forging, a high-temperature furnace sometimes referred to as the forge is required to heat ingots or billets. Owing to the size of the massive forging hammers and presses and the parts they can produce, as well as the dangers inherent in working with hot metal, a special building is frequently required to house the operation.
In the case of drop forging operations, provisions must be made to absorb the shock and vibration generated by the hammer. Most forging operations use metal-forming dies, which must be precisely machined and carefully heat-treated to correctly shape the workpiece, as well as to withstand the tremendous forces involved. There are many different kinds of forging processes available; however, they can be grouped into three main classes: . Common forging processes include: roll forging, swagingcoggingopen-die forging, impression-die forging close die forgingpress forging, cold forging automatic hot forging and upsetting.
All of the following forging processes can be performed at various temperatures; however, they are generally classified by whether the metal temperature is above or below the recrystallization temperature. The main advantage of hot forging is that it can be done more quickly and precisely, and as the metal is deformed work hardening effects are negated by the recrystallization process.
Cold forging typically results in work hardening of the piece. Drop forging is a forging process where a hammer is raised and then "dropped" onto the workpiece to deform it according to the shape of the die. There are two types of drop forging: open-die drop forging and closed-die drop forging.Cold forging is one of the most widely used chipless forming processes, often requiring no machining other than drilling.
The commonly accepted definition is the forming or forging of a bulk material at room temperature with no heating of the initial slug or inter-stages.
The term "no heating" does not include in-process annealing, which may be performed at intermediate stages to relieve the effects of work hardening. The process produces greater dimensional accuracy than hot forming, and does not produce scale.
However, the plastic flow characteristics of the workpiece are not as good, so that higher forging pressures are required. Component size is generally limited to 50 pounds or less. The majority of cold forgings weigh less than 10 pounds. Cold forging is being used in a wide variety of industries including fastener, automotive, pole-line hardware, truck-trailers, outboard engine controls, bicycle pedal cranks, constant velocity joints, universal joint crosses, and military projectile hardware.
Shapes generally have been limited to rotationally symmetrical and axisymmetric, including long shafts and struts. Shape capability is being expanded by developments in technology.
Some of the most common shapes and combinations of shapes are illustrated below in Section 5. Return to Table of Contents. Home 5. Return to Table of Contents '.Cold forging is a lot like hot forging except it is at or near room temperature. The lower temperature means that the steel is much stronger and it is much more difficult to forge.
That also means the steel is more brittle and therefore more likely to crack during forging or rolling. The shape of the grains in the steel are changed through forging. You can read about what grains are in this article.
Steel is made up of planes of iron atoms, and if the steel was made up of only one grain these planes of atoms would all be parallel to each other:.
However, there are many grains inside steel, and the boundaries between these grains are where the planes of atoms meet each other. During cold rolling we are pancaking those grains and elongating them. When forging a piece of steel the deformation is not quite as uniform, of course, but the principles are essentially the same.
At the same time the steel is being strengthened during the cold working process. Dislocations are atomic-level defects that control the mechanical properties of steel. You can read about them in this article. That is the same grain refinement article I linked to before but I have now doubled the chances you will be tricked into clicking on it. Steel always has dislocations, and different microstructures have a different density of dislocations.
Here is a short video of high resolution microscopy showing the movement of dislocations:. The strength of metals is controlled by how easily dislocations can move. Different features can prevent the movement of dislocations such as grain boundaries. So a fine grain size with many grain boundaries leads to higher strength because the dislocations are blocked by those boundaries.
Dislocations also cannot easily move through other dislocations, so a higher density of dislocations means higher strength because there are more of them that black the movement of others.
Martensite gets its strength, in part, from a very high density of dislocations. You can read about what makes martensite strong in this article. As steel is cold worked, more and more of those tiny atomic defects called dislocations are formed and the higher the density of those dislocations the stronger the steel is.
These dislocations should not be thought of as macroscopic defects or tiny cracks; dislocations are not bad, they are inherent to metals as the atomic structure is never going to be perfect.
When we start with annealed steel with soft ferrite and carbides, the structure looks something like below, with relatively round ferrite grains along with the smaller carbides carbides in different colors to differentiate :. The more energy is put into the steel more cold reduction the higher the driving force is for recrystallizing. That energy is stored in the steel primarily through the formation of dislocations.
So the energy is released from the steel by forming new grains with a low dislocation density. You can see the process of recrystallization in the video below:. If you watch carefully you can see that the new grains form on the white particles, which behave similarly to carbides in steel. The carbides promote the nucleation of recrystallized grains but they can also pin the recrystallizing grains, so the interaction of carbides and recrystallization is relatively complex.
Recrystallization occurs through the diffusion of iron atoms so a certain amount of temperature is required so that sufficient diffusion can take place. However, the temperature at which recrystallization starts is also controlled by the degree of cold work. The greater the degree of cold work, the lower the temperature is that recyrstallization starts :.
The rate of recrystallization is affected by temperature as well, where at higher temperatures diffusion is faster so the rate of recrystallization is also increased :. Again, this rate at different temperatures is dependent on the composition, carbides, and degree of cold work, but the above example provides some visual understanding of the difference with temperature.
All of this information is relevant because some knife steels are available in cold-rolled form and that can lead to some differences from hot rolled steel.
Cold Forging of Steel
There are a variety of reasons why cold rolled steel might be desirable, such as improved surface condition. Generally cold rolled steel has a bright, shiny surface free of scale. The thickness of the steel is typically also more consistent, and cold-rolled steel is frequently available in thinner sizes. AEB-L is usually available in cold-rolled form and some steel, among others.Cold working or cold forming is any metalworking process in which metal is shaped below its recrystallization temperatureusually at the ambient temperature.
Such processes are contrasted with hot working techniques like hot rollingforgingweldingetc. Cold forming techniques are usually classified into four major groups: squeezing, bending, drawing, and shearing. They generally have the advantage of being simpler to carry out than hot working techniques. Unlike hot working, cold working causes the crystal grains and inclusions to distort following the flow of the metal; which may cause work hardening and anisotropic material properties.
Work hardening makes the metal harderstifferand strongerbut less plasticand may cause cracks of the piece. The possible uses of cold forming are extremely varied, including large flat sheets, complex folded shapes, metal tubes, screw heads and threads, riveted joints, and much more.
The following is a list of cold forming processes:  : p. Advantages of cold working over hot working include:  : p. Depending on the material and extent of deformation, the increase in strength due to work hardening may be comparable to that of heat treating. Therefore, it is sometimes more economical to cold work a less costly and weaker metal than to hot work a more expensive metal that can be heat treated, especially if precision or a fine surface finish is required as well.
The cold working process also reduces waste as compared to machining, or even eliminates with near net shape methods. Production cycle times when cold working are very short. On multi-station machinery, production cycle times are even less.
This can be very advantageous for large production runs. Some disadvantages and problems of cold working are:  : p. The need for heavier and equipment and harder tools may make cold working suitable only for large volume manufacturing industry. The loss of plasticity due to work hardening may require intermediate annealingsand a final annealing to relieve residual stress and give the desired properties to the manufactured object.
These extra steps would negate some of the economic advantages of cold forming over hot forming. Cold worked items suffer from a phenomenon known as springbackor elastic springback. After the deforming force is removed from the workpiece, the workpiece springs back slightly. The amount a material springs back is equal to the yield strain the strain at the yield point for the material. Special precautions may be needed to maintain the general shape of the workpiece during cold working, such as shot peening and equal channel angular extrusion.
From Wikipedia, the free encyclopedia. Paul; Black, J T. Materials and Processes in Manufacturing 9th ed. Categories : Metalworking. Namespaces Article Talk.Cold forging is a manufacturing process where a bar stock is inserted into a die and squeezed with a second closed die. The deformation starts at room temperature and changes the shape and size of the initial part until it has assumed the shape of the die. The process requires high-resistance dies and high-duty steel, usually reinforced by retaining rings.
Even if these dies are quite expansive compared to hot forging dies, their life time is much higher, leading to a competitive cost per unit. However, this can only be achieved with a suited design and efficient forging process, thanks to excellent engineering skills. Not all steel grades can be cold forged. This leads to cost savings, especially significant in the high-volume production of small automotive components such as fasteners.
This is a highly automated manufacturing process and parts can be made economically. Another benefit of cold forging is the lack of grain growth and therefore perfectly aligned to the shape of the part metal grains with an exceptionally strong and resistant surface. After years of experience, technology research and investment Setforge owns best machinery and tooling for cold forging equipped with most precisely created dies.
We are one of the market leaders in the manufacturing of cold extruded shafts with up to 25 kg weight and mm length. Cold forging enables the manufacture of net shape or near net shape parts with a tolerance of tenths of millimeters in diameter, which makes the post forging machining especially cost efficient. Setforge Extrusion for medium and small batch production.
Setforge Near Net for high-volume serial parts. Over the years, Farinia Group has taken on new and tough challenges and built a solid expertise in the manufacturing of high-quality parts. Cold Forged Steel Grades Not all steel grades can be cold forged. Cold Forging Benefits This is a highly automated manufacturing process and parts can be made economically.
Our Expertise:. Hot Forging — Considerations, Benefits and Drawbacks. Do you need a similar component? Get In Touch. Casting FMGC. Additive Manufacturing Spartacus3D. Computing Services Safir. Engineering Setforge Engineering. Purchasing Approforge.