CNC machining can be completed with various materials, from plastic to aluminum, or stainless steel. The material choice is dependent on what your product is to be used for.
308 stainless steel steps in when you need something durable, tough, and corrosion-resistant. Here’s everything you need to know about it.
What Is 308 Stainless Steel?
308 stainless steel is an austenitic stainless steel. If you’re wondering, that’s a group of stainless steels which have excellent corrosion resistance.
This particular variant is made of iron, nickel, and chromium. The exact make-up varies, but it will be approximately 10% nickel and 20% chromium. There will also be small amounts of carbon, manganese, and silicon.
308 stainless steel, with its corrosion resistance and high-temperature resistance, is suitable for use in your CNC machining projects. You’ll also find this makes it a desirable option in many industries.
As well as strength and temperature resistance, 308 stainless steel is an excellent choice for welding. You’ll commonly find it used as a filler metal for welding, often with 304 stainless steel.
Physical And Mechanical Properties of 308 Stainless Steel
There are various physical and mechanical properties associated with 308 stainless steel. It’s good for you to know what they are as it will help you decide when this is the right material for your project.
- High strength to weight ratio, with a density of 7.9 g/cm cubed
- A melting point of between 1,400 and 1,455 °C
- Moderate linear thermal expansion
- Efficient at heating and cooling with a rate of 500 J/kg
- Low level electrical conductivity
- Non-magnetic except in cold-work conditions
- Moderate tensile strength of 585 MPa
- Yield strength of 205 MPa
- Moderate hardness
- Will elongate significantly if broken
- High level of corrosion resistance
- Stable material unless exposed to extreme pH levels, especially strong acid
- Can resist surface oxidisation at temperatures up to 800° C
- Generates its own protective oxide layer
- Non-flammable and non-combustible
Why Is 308 Stainless Steel A Good Choice For CNC Machining?
When it comes to CNC machining, you’ve probably already spotted that 308 stainless steel is not the cheapest option. However, in the right situation, you’ll find it is the best.
When you look at the above properties, you’ll quickly realise that this type of stainless steel works well in extreme environments, whether that’s high temperatures or even high pressure. It’s what makes it an attractive and viable option when CNC machining.
If you’re still unsure, consider this; 308 stainless steel has low cracking and doesn’t warp easily. That makes it an ideal choice for your CNC machining project. It’s strong, durable and easy to look after.
Types of CNC Machining That Work with 308 Stainless Steel
308 stainless steel is an excellent choice for all your CNC machining needs. When you use all the options available, you can create virtually any shape object.
Milling
The milling cutter is a rotary cutter. It usually has multiple cutting points and it moves into the steel. The angle, cut speed, and even the pressure can all be varied to get the result you desire.
You can use it to cut a face into a piece of material.
Drilling
When you need precise holes in your 308 stainless steel product, you need the CNC drill function.
Turning
CNC cutters have a single cutting point, which can be used to cut 308 stainless steel into cylinders. If you’re looking to make cylindrical parts, such as shafts you’ll appreciate this machining technique.
Grinding
As you know, all grades of stainless steel are tough. Grinding across the surface of the stainless steel removes just enough material to create the right depth. It’s an effective way for you to get a high-precision finish.
Benefits Of Using 308 Stainless Steel
You’ll find the benefits make it a popular choice in many industries and components.
Quality control
308 stainless steel is created to strict standards. The finished metal must have between 9-11% nickel and 19-21% chromium. In short, no matter how many times you order 308, you know you’re going to get the same quality every time.
That makes creating moulds and the right CNC cutting tools easier. This quality control transfers through to the finished product. Whether you’re machining hospital tools or automotive parts, you know the tensile strength, corrosion and temperature resistance, and that these factors won’t change.
It allows you to create high-quality products which makes it easier for you to build a good reputation.
Durability
When you choose 308 stainless steel you’re choosing a material that is built to last. It resists oxidisation at higher temperatures than many other alloys.
More than that, it doesn’t warp or crack easily. You can create products confident in the knowledge they will last.
That means 308 stainless steel will probably be the cost-effective option for your project. After all, if you can build a reputation for quality you’ll have an almost never-ending customer base.
Works in high temperature environments
You may already know that the main reason the aerospace industry uses 308 stainless steel is that it doesn’t change even when subjected to high temperatures. In fact, it can handle temperatures well below freezing as well as temperatures as high as 870° C
Considering the stress and heat exposure that aeroplanes and space rockets are placed under, you won’t find it surprising that these industries choose 308 stainless steel.
If you’re looking at making things that need to operate in high temperature zones, such as car parts or monitoring a volcano, you need to choose the highest-quality 308 stainless steel.
Good choice for welding
If you’ve ever undertaken industrial welding you’ll already know that 308 stainless steel is a popular and practical choice.
As well as being tough, its composition means it doesn’t suffer from carbide precipitation while you’re welding. Carbide precipitation reduces the corrosion resistance level of metals.
The fact it has minimal effect on 308 stainless steel means your welded product will be less likely to suffer corrosion. Remember that if your product is likely to regularly be in or close to water.
Can be hardened
Although 308 stainless steel already has a high tensile strength, you can harden it to improve its strength further.
Resistant to corrosion
As we’ve mentioned so many times, 308 stainless steel has a high resistance to corrosion. You’ll find that useful in an assortment of applications, such as products designated for the great outdoors
Disadvantages of Using 308 Stainless Steel
Nothing is perfect and there are some downsides to you CNC machining with 308 stainless steel
Can experience stress cracking
You’ll find 308 stainless steel has a low cracking rate. However, in certain environments, particularly when dealing with high levels of thermal stress, the metal and the weld can crack. That will seriously weaken your component.
Generally higher cost
The purer the stainless steel, the higher the cost. You’ll find 308 stainless steel costs more than many other types of stainless steel. However, if it’s the one that will do the job properly, you have to see it as a worthwhile investment.
Pits in high chloride environments
If you’ve ever seen stainless steel you’ll know it generally has a high-quality smooth finish. Unfortunately, high levels of chloride can cause the surface to become pitted. At best that’s unsightly, at worse, it could weaken the component and shorten its life.
If your 308 stainless steel parts are destined for high chloride environments, such as swimming pools, choose a different stainless steel variant.
Potential Issues When Using 308 Stainless Steel And How To Deal With Them
Machining with 308 stainless steel is straightforward, provided you have the right tools and are aware of potential issues.
Overheating
308 stainless steel is tolerant of high temperatures. However, you can heat it too much during machining. If you do so for an extended period, you can damage the structure of the steel.
Thermal heat can rise dramatically when machining as it is often metal against metal. Make sure you complete the machining in stages to avoid extended temperature spikes.
Hardness
The hardness of 308 stainless steel is one of it’s most desirable qualities. Unfortunately, this can also cause issues when machining. It’s important you use the right equipment when handling the metal.
Incorrect tools
An extension of hardness is your tool choice. It’s vital to choose tools designed to work with 308 stainless steel. They will cut more efficiently and accurately.
It will make the job easier and less likely to cause you heat or other issues.
Conclusion
You won’t be surprised to learn that 308 stainless steel is one of the most desirable alloys. It has plenty of good qualities and can be easy to work with. It’s also a practical choice for many industries.
Whatever product you’re trying to create, you’ll find 308 stainless steel is a good choice, just choose the right CNC machining tools and equipment.
FAQs
Here are some of the most commonly asked questions; they may give you the answer you need.
What’s the difference between 308 stainless steel and other grades?
The only real difference is the chemical composition. 308 stainless steel has 10% nickel and 20% chromium. Other versions of stainless steel have different amounts of these important elements.
Why is 308 stainless steel a good choice for machining?
The main reason is its qualities. By now, you should appreciate that 308 stainless steel is strong, has a high temperature tolerance, and is difficult to corrode.
That makes it an attractive option for almost any component you’re making – especially if they are likely to be used in high-stress environments.
Should I choose 308 stainless steel instead of aluminium?
This depends on the job you’re trying to do. Stainless steel is generally better at resisting corrosion and offers more strength. Of course, aluminium is much lighter.
Why does the grade of stainless steel matter?
The most common grades of stainless steel are 304, 308, and 316, but there are many others. The higher the number the greater the corrosion resistance: and the higher the cost.
All businesses need to balance cost with quality. The various grades of stainless steel help you to make the right cost and quality decision.
Where can I get assistance machining 308 stainless steel?
Contact our customer support team. We’ll be happy to help with all your needs, from machining to advice.
Is 308 stainless steel magnetic?
308 stainless steel has an austenitic crystal structure, you’ll quickly notice it will not usually be magentic or possible to magentize it.
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