The Egyptians introduced powder metallurgy a few hundred years ago, and have become one of the essential metal-forming processes alongside metal stamping. Most people are familiar with metal stamping since it’s a mainstay process for forming metal parts. Numerous manufacturers are also familiar with metal stamping since many of their products are custom-made from these processes. But while both metal forming techniques result in similar parts, what are they, and how do they compare? This metal stamping vs. powder metallurgy takes on these two processes, explaining the key differences and similarities.
Metal Stamping and Powder Metallurgy: What are They
Powder metallurgy involves compressing metal powder in high sintering temperatures using immense hydraulic or mechanical forces to form metals of various shapes and forms. It’s a process dating from ancient Egypt and has become one of the essential and sought-after metal-forming processes. However, this technique isn’t as popular as most metal forming processes like die casting metals stamping, although innumerable industries find it useful.
Metal stamping, however, transforms metal blocks into desired shapes using compressive hydraulic forces. The key variation between the two processes is that metal stamping uses solid metals in their natural state rather than powder form. However, the results are similar, and it’s not easy to distinguish the metals formed by the two processes. Nevertheless, it’s valid to argue that they may differ in their physical properties, but we’ll see how further in this article.
Powder Metallurgy: An Insight
Powder metallurgy uses intense heating and compression to bond metal powder, forming solid and shaped metal blocks. The process is almost as similar to hot die casting, only that it doesn’t use melted metal or compression. The temperature in the sintering process is usually high, compressing and compacting the metal powder into a solid. This heating gives the parts an enviable accuracy since the temperatures a marginally below the metals’ melting points.
Powder Metallurgy Processes
Powder metallurgy combines a few practical steps to create metal parts with high dimension accuracy. These metals have the chemical and physical properties typical to every meta type and are as robust as they should be. The powder usually undergoes immense compressive forces under extreme temperatures, bonding the powder particles together. Below is the powder metallurgy process.
Preparation of the Powder
Melt atomization produces the metal powder used in this process. Liquid metal is usually made into tiny droplets that cool and solidify, forming smaller particles. However, atomization isn’t the only technique used for producing metal powder. Other similar processes include grinding, electrolytic deposition, and chemical reduction. Usually, before advancing further into the process, the metal undergoes testing for strength, compressibility, density, and flow rate before it gets the nod.
Mixing and Blending
Mixing happens through rotating double cones, rotating drums, blade mixers, or screw mixers fixed inside a drum. The process combines several metal powders, lubricants, and binders to create metals with desired properties. This process is usually thorough and takes time to ensure that the powders and other substances mix evenly. The ratio of metal powders added to the mixture depends on the desired end characteristics of the metal part.
Compacting
Compacting usually comes after mixing and blending, and it’s the critical process of giving the metals their final properties. The compacting pressures can be as high as 1600 MPa, but this amount depends on the metal powder properties. Hard metal powders can use this immense pressure, typical for steel and iron. however, soft powder compacting pressure ranges between 100 MPa and 400 MPa.
Compacting determines the density of the final metal part, among other processes. It also reduces the potential voids by compressing the air pockets, making the metal robust. However, that should happen under strict guidelines since retaining these voids is highly likely during this process. Nevertheless, sintering makes the metal parts sturdier and improves their accuracy, making it a final routine process.
Sintering
Sintering uses extreme heat to forge proper bonding between the metal particle. That’s essential, especially if the metal will undergo intense sheer stress in its industrial applications. Although the immense compressive forces during compaction can be sufficient, it helps to be sure with sintering.
While the metal can be solid and compact after compression, heating doesn’t change its properties. Instead, it’s usually slightly below the melting point, facilitating a marginal flow of the molten particles within the metal structure. That ensures the pores left behind get filled up, improving the overall metal density. Sintering makes metals sturdier and more reliable when handling extreme pressure during various industrial applications.
Types of Powder Metallurgy Processes
Powder metallurgy is quite a simple process from a general perspective. However, a few techniques make it somewhat complicated and tailored to produce metal parts with varied characteristics, including shapes and forms. The powdered metallurgy types include the following:
Injection Molding Powder Metallurgy
Injection molding powder metallurgy is a process popular for metal part manufacturers who need high dimensional tolerances. It follows the general powdered metallurgy procedure, only that it uses an injection molding machine to inject the feedstock (the metal mixture). It produces metals having more complex shapes in high volumes.
The only drawback with injection molding powdered metallurgy is that it mainly prompts secondary finishing to remove the bars and smooth the edges. However, producing metal with exceptional geometries and incredible dimensional accuracies is quite a practical process.
Isostatic Pressing Powder Metallurgy
Isostatic pressing powder metallurgy applies equal pressure to every metal surface from all directions. That ensures that every point of the metal has a similar microstructure and density. Usually, that happens in various temperatures, creating two sub-processes: Hot and cold isostatic pressing.
Hot isostatic pressing combines high temperatures and pressure, eradicating porosity, bolstering mechanical properties, and increasing density. That ensures that the metal is sturdy and workable enough, able to withstand the sheer forces. The good thing about this subtype is that it helps minimize micro-shrinkage, a casting defect that’s not usually detectible at magnifications lower than ten diameters.
Conventional Powder Metallurgy (Press and Sinter)
Conventional powder metallurgy follows a similar general procedure but incorporates contemporary metal-forming technology. It involves mixing alloy powders with additives and lubricants or an elemental mixing to produce a homogenous mixture. This subtype ensures that the metals formed have high resistance, machinability, and lubricity.
Products and Parts Made by Metallurgy Processes
Powder metallurgy produces more complex parts, including connecting rods, fuel system components, catalytic reduction systems, and main bearing caps. It also creates steering and engine components used in the automotive industry and aerospace manufacturing. This process produces more complex geometries, and every part made is of the best quality. It’s preferable in some industries that require incredibly robust metal parts since metallurgy ultimately binds the metal particles with sturdier, unbreakable bonds.
Metal Types Used in Powder Metallurgy
Some metals used in powder metallurgy include stainless steel, nickel, copper, iron, aluminum, and titanium. These metals have the required physical capability to produce the best metals under this process and are easy to work with. They may sometimes be mixed to create more complex feedstock, mainly to strengthen them. Metal mixtures complement each other structural properties, improving their strength and capability to handle any sheer forces during their applications.
Metal Stamping: An Insight
Metal stamping uses pressure to shape metals in their natural states. The original properties aren’t altered but maintained as the compressive forces act on them. The blanks are usually placed on a die. Generally, a sturdy metal block is tooled to the desired form for making uniquely shaped metal parts. The temperature of these metals undergoing shaping (blanks) are usually in their natural state, and no heating is generally involved. Below is the metal stamping process.
Metal Stamping Process
Metal stamping is chronological and follows a series of steps to create more finished metal parts. Here’s the metal stamping process you should be familiar with.
Die Tooling
The die is the essential stamping machine component and contains the ridges and dents used in shaping the metal blanks. Dies are usually designed separately, but some metal stamping manufacturers do it in-house as their clients instruct. Die tooling involves using a computer numerical control (CNC) machine to create a custom design that shapes a metal blank.
However, computer-aided design (CAN) software usually does the designing, and metal stamping manufacturers use the provided design features to create the desired shapes. This process forms an algorithm traditionally fed into CNC machines and shapes the dies according to what a manufacturer wants.
Pressing and Stamping
Stamping uses pressure from a hydraulic system or mechanical forces generated through rotary mechanical action. This pressure is usually immense to shape metals in their original state, forming the desired part. Usually, some stamping operations combine several stations with different tasks like cutting, bending, and coining, while others do it in isolated stamping stations.
Finishing
Some stamping operations, like progressive die stamping, may not require this process. However, others may need these final touches to make the parts more usable and readier for industrial applications. Finishing includes polishing to remove the burrs and make the edges smoother and more aesthetic. Some other finishing operations include painting and color coating to minimize the chances of rust and corrosion once the metal parts hit the market.
Types of Metal Stamping Processes
The several metal stamping processes common in metal manufacturing include:
Multi-Slide Stamping
Multi-slide stamping, also known as four-slide stamping, uses vertical alignments to shape metal blanks. It uses four tools that use cam rotations to simultaneously shape the metal blank and is ideal for producing high-volume runs.
Progressive Die Stamping
Progressive die stamping combines several operations in a single die, with each ram performing a different procedure. A destacker usually feeds the metal coil from the receiving end and moves it along to every station for coining, bending, and cutting, among others, in a sequence. Every ram performs a different operation, and the process is continuous. The most significant advantage of this process is that it creates high-precision metal parts and is also ideal for producing high-volume metal rams.
Transfer Die Stamping
Transfer die stamping isn’t any different from progress die stamping, but the key variation is how the metal part moves from one station to the other. A conveyer belt transfers the metal part from one station to the other for cutting or bending, among other operations. However, the metal parts might have to undergo some finishing touches to give them a better aesthetic appeal.
Products and Parts from Metal Stamping Processes
Stamping metal parts are used in numerous automotive, aerospace, and electronics industries. These include bearing components, metal cups and cans, metal housing enclosures, and other various shapes. The different metal stamping processes coin their use, making them more specific to some industrial applications.
Metals Used in Metal Stamping
The common metals used in metal stamping operations should withstand the sheer forces and the pressure they’re subjected to. Aluminum is the commonly used metal since, besides being able to stand the tension, it’s less costly and perfect for high-speed production. However, stainless steel, carbon steel, copper, and brass are commonly used metal parts in stamping operations.
What is the Crucial Difference Between Metals Tamping and Powder Metallurgy?
Stamping operations use pressure as the principal force for shaping metals. The metals usually get subjected to pressure in their natural state and undergo transformation under high tension. On the other hand, powder metallurgy combines high pressure and temperatures, compressing metal powder into a single solid.
High precision is guaranteed in both processes. However, it takes an effort to realize that in some metal stamping operations. Powder metallurgy parts usually honor high dimensional accuracies in a single operation compared to some stamping operations to smooth the edges and remove burrs. Other differences include the types of metal combinations used, the products, and their various application.
Conclusion
Powder metallurgy and metal stamping all produce similar metal parts. However, the metal forming processes are varied, with stamping starting with solid metal. Powder metallurgy uses powder metal and compresses it to create a readily shaped part. Both methods guarantee high-quality parts and share some of the industries both serve.
