What is machinability, and why does it matter?
For finished components, machining operations generally make up a large proportion of their total cost. That is why machinability is a critical aspect of metal cutting operations that require:
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Good chip control
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Reliable cutting action
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Long and consistent tool life
One challenge with determining machinability is that there is no absolute definition of machinability in grades or numbers. By “good machinability” we usually mean undisturbed cutting action and a reasonable tool life. Generally, to evaluate the machinability of a certain material, we rely on practical tests, and the results are compared with other materials machined under the same conditions.
How does lead improve machinability?
Lead (Pb) was first added to steels in the early 1900s to facilitate high throughput machining operations. Adding lead and sulfur, both up to about 0.3%, was found to:
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Lower cutting forces
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Improve chip control
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Extend tool life
This created “free-cutting” steel. This was at a time when cutting tools were mostly made of high-speed steels, with metal removal rates often 1/50-1/20th of the cutting rates common today. Hence, the machining costs per component produced were substantially higher than they are today.
In the 1970s, carbide tools with ceramic coatings were introduced. In addition, tools with exchangeable inserts made machine shop operations more efficient. At the same time, steel making operations improved, while demand for higher quality steels increased. This resulted in the development of more low sulfur alloyed steels. At the same time, lead started to be phased out from many components, for reasons of mechanical strength and toughness.
Today, there is still a substantial segment of steel products manufactured from free-cutting steels with added lead. These parts are typically mass-produced, with a focus more on their geometry rather than durability. Now though, many producers of finished steel products are considering moving away from leaded steel due to its toxicity and environmental impact. It is a surprise that this transition hasn't happened sooner, since lead has been the subject of industry discussions dating back to the 1990s. However, there is now increasing regulatory and industry pressure to reduce or eliminate the use of lead in various materials.
How can M-steel replace leaded steel?
Our M-Steel is a great way to eliminate the need for lead in steel. It is a well-proven treatment that can be applied to any steel grade and any as-delivered condition. While it is often thought of as a solution for round bar, our tests show that it also works well for flat bar.
The M-Steel treatment is based on the modification and control of non-metallic inclusions with calcium treatment. A protective layer, originating from these calcium inclusions, is deposited on the cutting tool during machining. This deposit:
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Reduces the chemical wear of the tool from the passing steel
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Acts as a thermal barrier so more heat is carried away with the chip and less heat flows into the cutting tool
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Helps hot chips curl more, displaying better chip breaking
By enabling cutting speeds up to 30% faster than conventional steel, M-Steel meets the market demand for lower processing costs. In many circumstances, the tool life span can be more than doubled when machining components from M-Steel. This not only saves on actual machining time but also reduces the true cost per component. Tool life and operational efficiency are also factors that have an impact on a business’s profitability.
M-Steel ensures consistent machinability from heat to heat, meaning that machines can be run with fixed high cutting rates and predictable tool change intervals from one production run to another. This makes it very suitable for un-manned automated production.
While it is true that M-Steel treatment is an added cost on raw materials, it actually reduces the overall cost of machining. Some customers using our M-Steel have recorded a 30-40% reduction in total machining costs compared with conventional steel.
Research project in Denmark is evaluating M-steel
We have submitted our M-Steel for evaluation in the current Environmentally Friendly Steel project coordinated by DAMRC (Danish Advanced Manufacturing Research Center). The project is sponsored by machining companies in Denmark who face challenges in making the transition away from leaded steels.
The project is evaluating alternatives to leaded steel in the mass production of precision parts, such as quick-connect couplings and manifolds for hydraulic and pneumatic components. The program will test round, flat, and square steel products. We will publish the findings when this project is concluded.
Our Machining Cost Calculator illustrates the M-steel difference
To help you understand the difference that M-Steel can make to your productivity, we have developed a machining cost calculator as part of our overall Steel Navigator. All you need to do is enter all the details related to your own operations. You will then get an immediate illustration of the benefits that M-Steel can offer compared with your existing material.
Try the Machining Cost Calculator
More information about M-Steel is available here:
