Advantages and Disadvantages of Hot and Cold Forging- A brief analysis
Forging is fundamentally the process of shaping a metal for creating a shape using precise and specialized tools and equipment. The desired predetermined shape is realized using hot forging or cold forging.
Forging improves the metal structure by refining its grain size; no other deformation process is capable of developing such an optimal combination of properties.
Aluminium Forging takes aluminium as the raw material and subjects it to hot deformation in order to refine the metallurgical structure.
The forging process is classified into 3 major processes: hot, warm and cold. For the purpose of discussion, we will try to explain Hot and Cold forging in this article.
As the name suggests, hot forging employs extreme amount of heat for fabricating parts. Aluminium and al-alloys need an average temperature range of 360 to 520 degrees Celsius while Copper and its alloys require 700 to 800 degree Celsius of heat for molding.
Such a high temperature is necessary to avoid strain hardening of metal during the deformation process. Also important is to bring the process of Isothermal Forging that is used for super alloys to prevent oxidation of certain metals. Isothermal forging is hot forging within a controlled environment- as if working in a vacuum.
Hot Forging is typically used to fabricate parts that are used in the technical field and for metals that are characterized by a high formability ratio.
Major advantages of hot forging include increased ductility, more flexibility vis-à-vis cold forging and an excellent surface quality that results in a wider range of finishing work such as polishing, painting or coating as per individual requirement.
Among the disadvantages of hot forging process are a less precise dimensional tolerance and possible warping of the material if the cooling process is not performed carefully and under special conditions. There also is the lurking possibility of metal reacting with the surrounding atmosphere; hence it is advisable to take every possible precaution during the hot forging process.
It’s the process of deformation where the process is carried out below the recrystallization point. Before the name conjures up images of ice and snow, it will be prudent to remind that the process is carried out at room temperature, and usually with soft metals like aluminium and carbon alloy steels.
Most well-known among cold forging is the process called Impression Die Forging where the metal after being placed in a die is hammered by continuous strokes to force it into the die and form the desired shape.
Quite often, the cold forged aluminium piece is heat treated to increase strength- the process is called Tempering.
Cold forged products require very little or no finishing, thus saving on substantial costs as compared to hot forging. Another portion of savings ensue due to the precise shape possible with cold forging. These two major advantages combine with high production rate and long die life have converted many a manufacturers from hot to cold forging.
As the saying goes- everything cheaper is not always preferred. The main disadvantage of cold forging is that it can only forge simple shapes in high volume. Hence if a customer is looking at a highly customized shape, cold forging will have to hibernate to cold storage. Corollary to the first point is the fact that cold forged products are less ductile than hot forged components.
The main difference between hot and cold forging is strain hardening. While hot forging provides optimum strength and increased ductility, cold forging imparts strain hardening at room temperature. The choice between the two is usually dependent on economic rather than quality concerns- a simple product with high volume is an obvious candidate for cold forging while a complex customized component will require hot forging.
Pyrocast India is qualified to provide both types of forging solutions based on customer requirements. We make it a point to discuss the possibilities and articulate suggestions accordingly.