To raise the bar for performance or cost efficiency in any manufacturing design, you must first learn the basics.
For example, if you want to replace a structural machined, stamped, or forged part with a powder metal part, you need to consider various design for manufacturability (DFM) adjustments. Before production, your powder metal parts supplier should ask you a lot of questions—and you should ask your supplier just as many questions.
What are the possibilities for powder metallurgy (PM) structural parts? You'd be surprised - but you'll never know if you don't understand the basics first.
Think of this as your quick reference manual for powder metallurgy design of structural parts.
What are structural parts?
In powder metallurgy, a structural component describes a part or component designed to carry and withstand mechanical loads and stresses within a larger structure or assembly. Structural components are designed to provide strength, rigidity, and support to the entire finished structure or assembly.
The strength of structural powder metal parts comes from selecting the appropriate metal powder (and resulting microstructure) combined with compaction and sintering strategies. Strength increases tensile strength, yield strength, and hardness.
Manufacturing structural components using powder metallurgy offers many additional benefits, including tight tolerances, dimensional accuracy, consistency and the ability to meet all production volume requirements. A major benefit of using powdered metal to manufacture sintered metal parts is that it is cost-effective due to high material utilization. The ability to produce structural components to tight tolerances also eliminates or reduces the need for additional operations, often saving production time and costs.
Powdered metal produces virtually no waste and is a green process because it uses low energy, minimizes scrap, and is more economical than standard machining, casting, or most other metal forming techniques. Material selection for small structural components can optimize the performance of the component for its intended application with little change to the manufacturing process.
At H&Z, our team not only has an in-depth understanding of the manufacturing of sintered metal components. We also offer high-level expertise in engineering and materials science regarding powder metallurgy. This means we can recommend metal powders to help our customers design small metal parts to optimize performance. When correctly selected materials are combined with appropriate process parameters, the result is a finished structural component that meets the application requirements and provides proven cost savings compared to other metal forming options. This method is ideal for high-volume applications because there is little variation in the geometry formed by the mold.
Advantages of powder metallurgy structural parts
Other benefits of using powder metallurgy technology to manufacture structural components include:
•Reduce tool costs
•consistent reproducibility
•Tighter tolerances compared to castings and stampings
•as a cost-effective manufacturing process
•Able to adapt to production from small to large (annual output from 5,000 to more than 5 million)
Additionally, powder metallurgy design features eliminate the need for draft and shear forces necessary for cast or stamped designs.
Structural component applications
| Application areas | Application of powder metallurgy structural parts |
|---|---|
| Car manufacturer | Engine parts (crankshafts, connecting rods), brake system components, gears |
| Motorcycle manufacturing | Crankshaft, clutch gear, brake disc, sprocket |
| Aerospace | Engine parts, aircraft landing gear, fuel system components |
| Medical equipment | Surgical tools, implantable instruments, X-ray protective equipment |
| Electronic and electrical equipment manufacturing | Control rods, hinge components, bearings, cameras, electric motors, motor cores,Gears, stators, bearings |
| Military and defense | Weapons parts, protective equipment, missile components |
| Electrical tools | Gears, motor parts, housings, pawls |
| Machine made | Pumps, valves, bearings, gearboxes, cylinder liners |
| Steel manufacturing | Wear-resistant parts, corrosion-resistant parts, filter elements |
| Construction and building materials | Building connections, anchoring equipment, structural supports |
Materials used to make structural components
The powder metallurgy process starts with the collection of metal powder particles.
Metal powders are engineering materials that meet a wide range of performance requirements. Understanding powder is crucial in powder metallurgy as it is a critical input in producing the final metal part.
Powders are produced by solid-state reduction, atomization (gas, water or centrifugation), electrolysis or chemical treatment of metallic materials.
Fogging is the typical method used today. It involves converting molten metal into a spray of droplets, which then solidifies into a powder. Water atomization is the most common form of atomization because it produces irregularly shaped particles, which facilitates compaction for powder metal part production.
Metal powders are divided into elemental powders, partially alloyed powders or pre-alloyed powders. Elemental powder is the granular form of pure metal powder. They are the building blocks for making alloys and composite materials. Partially alloyed powders are mixtures of elemental powders of different materials mixed together, while pre-alloyed materials are alloyed states produced by atomizing a combination of metals.
In most cases, the powder mix, whether elemental or pre-alloyed, also contains additives (lubricants or binders) to extend tool life, help parts eject from compaction molds, or to hold metal parts in place prior to the sintering process together. These additives are removed from the parts that require the sintering process.
The geometry of an individual powder is determined by particle shape and internal structure, particle size and distribution, and surface area. Particles come in a variety of shapes, including spherical, irregular, flake, dendritic and sponge-like. The distribution of particle sizes in a powder affects compaction because smaller particles will fill the voids between larger particles. This size combination improves compaction density and material properties.
These are critical parameters in powder metallurgy as they determine the behavior of the powder during mold filling, compaction and sintering. These factors must be optimized to achieve the required strength and density both in the green stage and in the final sintered part.
Powder materials for structural applications
Iron powder is the most commonly used material in structural applications. It can be used alone but is often combined with other alloy materials to improve mechanical properties. Common additives are carbon, copper, nickel and molybdenum.
Carbon steel is made from a mixture of iron powder and graphite powder. During the sintering process, the graphite is absorbed by the iron, forming a steel structure. Pre-alloyed carbon steel is also available for suitable applications.
Copper steel is produced by adding copper powder to iron powder. The result is increased strength and stiffness.
Nickel steel added to iron powder (with or without copper powder) produces high-strength parts with good fatigue strength.
Other additives in iron powder can include infiltrating lower melting point materials such as copper to increase density and enhance impact resistance. Adding small amounts of phosphorus improves electromagnetic properties and provides ductility and strength.
Low alloy steel and diffusion alloy steel are made from pre-alloyed steel powder using nickel, molybdenum and manganese. This mixture is used when high performance and high hardenability are required in structural components.
Electromagnetic materials are used when components require good magnetic permeability, purity and density.
Stainless steel powder metal is required when parts and/or applications require significant mechanical properties and high corrosion resistance.
Copper substrates include pure copper, brass, bronze, nickel silver, etc. Each of these powders is selected for its specific properties, such as electrical or thermal conductivity, oil impregnation, machinability, ductility or corrosion resistance.
Aluminum powder has good corrosion resistance, excellent surface treatment properties, high strength and stiffness to weight ratio, and vibration and sound insulation properties.
Summarize
At H&Z we manufacture precision sintered metal structural components from small batch requirements to very large requirements. The pressed metal process is ideal for small structural components with complex geometries and tight tolerances. Our state-of-the-art metallurgical capabilities, coupled with a highly educated and experienced metallurgical staff, ensure finished products meet your exact specifications. H&Z can also discuss converting your parts from other metal forming technologies to powder metal manufacturing.
Our experienced team has many years of industry knowledge and is ready to assist with sintered metal component product development, design and material selection. H&Z will optimize multi-stage designs with tight tolerances, minimizing the secondary operations required to manufacture the finished product.
As a manufacturer of powder metal parts, H&Z not only produces structural parts, but also metal parts such as metal gears and powder metal bearings.
