In sheet metal fabrication, the selection of materials directly determines the manufacturability of parts, costs and performance. In engineering aspect, soft metal indicates the metal that has lower yield strength and higher elongation at break. This type of metal can be formed or machined and it is not easy to occur cracking. Now let us explore the features of soft metals.
What Are Soft Metals?
In fact, soft metal is not a formal name in material science. It is an engineering concept based on the performance. In manufacturing field, soft metal means the metal and alloys that have low hardness, high plasticity and good ductility, these mechanical properties make soft metals easy to deform. It is commonly used for bending because of its high plasticity and high ductility.
Soft metal vs lightweight metal: Are they the same?
Are you confused about soft metals and lightweight metals? As a matter of fact, soft metals and lightweight metals are not the same material.
Key Difference between Soft Metal and Lightweight Metal
Soft metal like pure aluminum, pure copper highlights the mechanical properties of materials, while lightweight metals like aluminum, titanium focus on physical properties of materials. Here you can easily find that aluminum is not only soft metal, but also hard metal. But titanium is only lightweight metal, but not soft metal. Also, some metal can be soft metal and lightweight metal, but the definitions of them are different.
Application of Soft Metals and Lightweight Metals
Soft metals are suitable for bending, forming and machining that require high ductility. While lightweight metals are often used in special industries such as aerospace and automotive that have high requirement for light weight.
Hard vs Soft Metals: What Are Key Differences?
Many people are confused by hard and soft metal. Differing hard metals from soft metals is very essential for engineers because it can directly determine the design and functions of final parts. Importantly, the manufacturing methods of soft metals and hard metals are different as well. So here let us classify their differences so that you can understand easily.
| comparison | Soft metal | hard metal |
| hardness & Strength | low hardness(about 20-40 HB) lower tensile strength unclear yield point |
high hardness(about 200 HB) higher tensile strength clear yield point |
| Formability/Bendability | Excellent low bending force small springback precision angles |
high bending force unpredictable springback prone to cracking(large bend radius) |
| Applications | Low cost lightweight parts |
high cost high-srength, wear-resistant, corrosion-resistant structural components |
By knowing the key differences in the above table, engineers can easily choose suitable metals for specific manufacturing.
Why You Need Soften or Harden Metals?
Can hard metal be soften? Or can soft metal be harden? Actually, both of them can achieve. However, why not choose soft metal or hard metal directly? Is it necessary to soften or harden the metals? In fact, not all metals have ideal desired hardness, strength, and ductility. For example, the soft metal with ideal hardness may by too expensive. As for bending, some metals have ideal properties but are difficult to manufacture.
Reasons for Softening Hard Metals:
- Hard metal is difficult to cut and bend due to its high hardness.(Purpose: make it easy to manufacture)
- The precision can be easier to control after heat treatment.
Reasons for Hardening Soft Metals:
- Soft metal is easy to machine but its strength and wear resistance are insufficient.(Purpose: for improving performance)
- Harden soft metals can prolong lifespan and improve load-bearing capacity of a part.
How to Soften Hard Metal?
Soften hard metal to make it easier to machine, bend and form. Heat treatment like annealing, tempering, and normalizing is usually used to soften hard metal.
Annealing
Heat the meta up to specific temperature and keep for a period of time, then cool it slowly to reduce hardness. Pure copper is typically heated to 500-700°C, but aluminum alloy is heated to low temperature about 350-420°C. The temperature needs to be controlled strictly.
Tempering
This method is mainly for steel. After hardening, heat to a lower temperature to reduce brittleness while keeping some strength.
Normalizing
Heat the metal above its critical temperature, then air-cool to refine grain structure and relieve internal stresses.
How to Harden Soft Metal?
In contrast to softening, sometimes we want to improve the strength and elasticity of parts after bending. Some soft metals like pure aluminum and copper can’t be hardened by heat treatment. The primary method is work hardening. However, the work hardening of metals is limited. Excessive hardening can lead to loss of plasticity, reduced toughness, and ultimately brittle fracture under stress.
What Are Soft Metals Used for?
In which industries is it used? Soft metal is used in many applications based on three impressive engineering features:
- Superior Electrical and thermal conductivity
- Excellent plastic forming capability
- Specific chemical stability
Electrical Industry
Soft metal such as pure copper and aluminum are widely used for making bus bar because their optimal electrical conductivity. Copper bus bar and aluminum bus bar are manufactured by metal bending technique.
Automotive Industries
Aluminum alloys and copper are soft and used for manufacturing lightweight parts such as some auto structure components, auto housing, heat sink, etc.
Aerospace Industries
Aluminum alloy is the typical metal used for making aircraft shell, cold plate, and brackets and so on because of its high strength and light weight.
What Are the Common Soft Metals?
In engineering practice, several soft metals and alloys are commonly used for bending parts.
Pure Aluminum (1xxx Series)
1100 and 1050 have excellent formability and weldability, widely used for making complex bent parts. Aluminum can be bent into enclosures for electronics, heat sinks, and mounting plates.
Pure Copper (T2)
It has incomparable electrical and thermal conductivity, usually used for making electrical connectors, terminals, and heat conductive parts, etc.
Brass(H62)
It is harder than pure copper. It is usually used for precision mechanical components, decorative fittings and mounting brackets because of its good corrosion resistance and good appearance.
AI-Mg Alloy(5xxx Series)
It is the most common material for sheet metal bending. It not only has good formability, but also higher strength than pure aluminum. It is very suitable for manufacturing structural brackets.
Properties of Soft Metals
Soft metals dominate bending forming processes due to their great physical and mechanical properties. The physical and mechanical properties of soft metals include:
Low Yield Strength
It means that it takes a small amount of stress to cause permanent deformation. In other words, the metal can be easily bent without springback. This is helpful to control the geometry of parts, and the precision of parts can be improved.
High Elongation
Soft metals usually exhibit post-break elongation rates. This means that soft metals can be stretched at the outer edge during bending without cracking. It is the key parameter for evaluating whether the material is suitable for small-radius bending.
Good Thermal Conductivity
During high-speed bending, the heat can be quickly transferred, which can reduce the change of material properties caused by local temperature rise.
Advantages of Soft Metals
From engineer’s perspective, there are obvious advantages of selecting soft metals for bending parts. Here are some advantages:
- High Precision of Parts: Soft metals can lead to little springback and the structure is stable. It is easier to control the final angle and dimensions of the finished parts by adjusting bending parameters, like bending angle compensation, which is crucial for precision assembly.
- High Design Flexibility: Smaller bending radii can be achieved, which means parts with complex geometries can be easily bent.
- Energy Efficiency: Both cutting and bending processes require minimal mechanical force, which can reduce energy consumption and bending time.
결론
In precision manufacturing, soft metal takes advantages of its low yield strength, high elongation rates, and excellent machinability. Successful bending depends on the understanding of soft metal’s properties, but also the methods for softening or hardening metals. When designing and manufacturing soft metal, the most suitable materials should be selected scientifically based on the functions of parts, application environments and budget.
Tuofa metal bending hope this guide will assist engineers and procurement professionals in mastering soft metal bending forming processes with greater precision and confidence for future projects.
FAQ
Are Soft Metals Bendable?
Yes, soft metal is very suitable for bending or forming process. However, some factors like heat treatment can influence the bending. So when bending soft metals, you should consider the situation of metals.
How to Choose Suitable Soft Metals for Bending?
Selecting suitable soft metal for bending parts should following the following steps:
- Determine the requirement of parts: the requirements include electrical or thermal conductivity, strength and weight, corrosion resistance requirement, cost control.
- Evaluate the bendability of metals: make sure the designed bending radius is greater than or equal to the minimum value of material. Although soft metal has little springback, it is still necessary to calculate it in high precision bending. The higher the yield strength of the material, the lower the elastic modulus, and the greater the springback.
Are pure metals soft?
Not all pure metals are soft, but many of them are relatively soft compared to their alloys.