What’s the purpose of heat treating springs exactly? This is an important process that should be understood accurately. Read on.
Raw spring materials have to go through multiple steps in order to bring them to a satisfactory and finished product. One of these steps is heat treatment. The spring manufacturer puts the last touches on the material in order to ensure it is as efficient as possible for a specific desired application.
Heat treatment refers to the tightly controlled activity that involves heating and cooling a particular material in order to arrive at considerably improved and desired chemical, mechanical, and physical properties. Some color changes may also occur by the time this process comes to an end.
Although metals undergo numerous heat treatment during production and refinement, it is left to the spring engineers to complete the last or final treatments, which is often based primarily on the client’s specifications.
Heat treating metals – such as springs – has to do with controlling the size of the metal’s grain structure or microstructure, thereby improving properties such as shear strength, toughness, and tensile strength.
In the case of springs, in particular, this could mean boosting the working life of a highly durable commodity or product with enhanced wear resistance as well as higher loads. It could also imply surface hardness, increased ductility, temperature resistance, etc.
The Heat Treatment Process
Heat treatment is one of the most crucial phases of the metal manufacturing process. This is primarily because it helps to significantly enhance a metal part – including springs – in order to better combat wear and tear.
It is not all materials that undergo heat treatment the same way. In this case, it is very important to, first of all, understand the primary purpose of your application as well as the operating environment of the spring.
When these are fully understood, the next step will be to select the most appropriate process that applies to your particular spring.
Why You Should Heat Treat Springs
All springs need to undergo heat treatment in one way or another in order to relieve the overall stresses that coiling induces significantly. Some materials require heat treatment in less than 4 hours of coiling, while others have multi-stage heat treatments or undergo hardening by precipitation.
All these processes are highly essential to the overall performance of any spring. Nearly every in-house heat treatment of springs must be verified via mechanical tests that help ensure that the material has attained its maximum or desired properties post heat treatment.
Uniformity is never a guarantee for any spring heat treatment that involves the use of conveyor ovens.
Different Types of Heat Treatment
Heat treatment serves as an umbrella term in the context of metal preparation for springs and precision wire products.
There are up to 3 major types of heat treatment utilized in spring manufacturing:
- Aging
- Annealing
- Stress Relieving
Let’s discuss them briefly, one after the other.
1. Aging
Aging – in reference to heat treatment – gives room for a change in the properties of specific alloys and metals. These are changes that occur at elevated and ambient temperatures after cold working or heat treating metals.
When the properties of these materials change, it is often a result of precision – i.e., a phase change. It is generally never involved in the change in the chemical composition of the alloy or metal.
Aging is a heat treatment process employed to boost a metal’s yield and tensile strengths to a much higher level than the unaltered material.
2. Annealing
Annealing is a heat treatment process that involves the softening of metals or achieving several changes in the material’s microstructure. The process has to do with heating a particular metal and then holding its temperature at that specified level. After a pre-set period, the metal is cooled at a particular rate.
Annealing has 3 stages:
- Recovery
- Recrystallization
- Grain growth
The primary purpose of this heat treatment process is to minimize the hardness of the metal. This makes the metal much easier to form and malleable. Spring manufacturers use annealing only if its parent metal has a low tensile strength that must be worked significantly.
3. Stress Relieving
Stress relieving shares some similarities with annealing given that the metals are usually heated until it reaches an appropriate temperature and then cooled readily at a specified rate.
The only difference between stress relieving and annealing is that the temperature of the metal is maintained at an incredibly high level for prolonged periods. This helps to minimize its residual stress before it is cooled slowly in order to prevent the formation of new residual stress.
Any metal that undergoes the stress relieving process has much better machinability. This means that such metals have a higher flatness standard as they can easily be cut.
Spring manufacturers generally use this process to relieve stress in the springs they create and return them to a normal state right after the forming operation. This can enhance the overall strength of the metal or material to a higher point before forming.
Advantages of Heat Treating Springs
Heat treating springs has several advantages, which are outlined below:
- It engenders a more durable, high-quality spring.
- It enhances wear-resistance.
- It boosts the overall lifetime of the spring.
- It increases the spring’s shear strength, toughness, and tensile strength.
- It leads to a significantly improved fatigue life.
- It increases its ductility.
- It affects the unique properties of the material, such as elasticity, hardness, etc.
You can experience some or all these benefits, depending on the application of the spring or its intended purpose. The heat-treating process springs undergo – irrespective of the type of heat treatment administered – leaves lasting effects on the material.
Final Thoughts
As you can see, heat treating springs is a vital process that every spring manufacturer does not trifle with. This closely controlled process is required during spring manufacturing in order to bring out the best properties that the metal has to offer. The advantages of heat treating springs show how vital the process is in this industry.
This makes the finished product easier to use for a specified purpose as properties such as shear strength, toughness, and tensile strength are considerably improved for maximum effectiveness.