PRODUCTS & EQUIPMENT
Machining a stainless steel pipe before welding with a PROTEM SE60 beveling machine
iron, titanium or aluminum. These alloys have the same advantages as stainless steels, but to a greater extent. Specifically, their heat resistance is higher (about 900°C) as is their corrosion resistance (corrosion in chlorine ion solutions, ultrapure water and caustic mediums). They are also much more expensive than standard alloys, but this is justified for applications where operator safety is an essential criterion. Pipes made from nickel-based superalloys are used in aerospace (in combustion chambers, for example), the chemical industry (due to their corrosion resistance), nuclear engineering, and, to a lesser extent, in the food industry. Superalloys are considered very difficult to machine. This can be attributed to several factors. First, one must bear in mind that 70% of the heat is returned directly to the cutting tool (as opposed to 15% for standard steel, for example). Therefore, it is essential to keep the cutting-edge cooled during machining. The second complication
is the hardness of the material; in fact, the lifetime of a cutting tool used to machine a superalloy can be reduced to just a few minutes if the tool does not have the necessary power, or if the cutting speeds and tools are not suitable.
Titanium Titanium is an extremely interesting metal for the industry. Titanium can be used to manufacture pipes which are light and yet highly resistant to corrosion and able to withstand very high temperatures (600°C). Its mechanical properties (resistance, fatigue and ductility) are also appreciated. Titanium is, however, expensive and this limits its use to specific applications. In general, one finds titanium in the aerospace sector where its low density combined with its attractive mechanical properties make it an essential material. Since the thermal conductivity
of titanium is very low (about ten times lower than steel), the heat dissipation during machining is
Machining with superalloys, PROTEM TTNG 1016 Orbital Tube Cutting & Beveling machine
relatively poor. Therefore, the cutting edge needs to be properly cooled to avoid machining defects. Sharp tools should be used to facilitate chip detachment from the material, and thus reduce the cutting force. Machining is even more difficult
in the case of treated titanium (e.g., treatment by precipitation hardening, presence of chromium coating or alloying).
Aluminum Aluminum is very widely used in the industry. Aluminum pipes are inexpensive, easy to form and assemble. They are also light and corrosion-resistant, making them a natural choice in the aeronautics, transport and construction sectors. Aluminum pipes are also used to build compressed-air pipelines. Aluminum pipes have a very low
level of hardness, and are therefore relatively easy to machine. However, the malleability of aluminum can cause problems (shavings can lead to machine jamming, for example). In this case, the best response is to increase the cutting speed, the depth of the pass and the feeding speed. There is also a risk of aluminum pipes being deformed during machining if the machine tool, and in particular, the clamping jaws, are not correctly chosen. The high thermal conductivity of aluminum allows for good heat dissipation. Thus, the cutting speed can be increased without reducing the lifetime of the tools.
Protem SAS
www.protem.fr Mathieu Schram, Graduate of the Arts et Métiers Engineering School
Titanium-elbow machining for the Aeronautics sector, PROTEM SE 2T pipe-squaring machine
10 IMT June 2016
Drawn aluminum pipe with PROTEM SE 90 pipe-squaring machine
www.internationalmetaltube.com
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