304L Stainless Steel Pipe is made of iron and carbon, just like standard steels, to which chromium is added which beyond a certain proportion (10.5%) allows the formation of a chromium oxide layer.
Other elements can be added to improve the mechanical strength (Nickel) or the high-temperature resistance (Molybdenum, Titanium, Vanadium, Tungsten).
Although at a higher cost than standard steel tubes, stainless steel tubes are widely used in a large number of industries such as the chemical, petroleum, pharmaceutical, aeronautic, shipbuilding industry, etc.
Indeed, api 5l grade b resistance to corrosion and their chemical stability make it possible to use these tubes for fluids which must not be contaminated, such as those used in the pharmaceutical industry or the food industry or corrosive fluids as the found especially in the chemical industry.
The machining of stainless steel is highly dependent on the proportion of alloying elements. A high proportion of chromium, nickel or titanium will make machining more difficult, while elements such as carbon or sulphur will facilitate machining.
1.Superalloys
The superalloys used in the manufacture of tubes are mostly part of the range of nickel-base superalloys.
The base of the 304 Stainless Steel Pipe is, therefore, nickel which can be alloyed with chromium, iron, titanium or aluminium. These alloys have the same advantages as stainless steels but in a more significant way. In fact, their heat resistance is higher as is their resistance to corrosion (corrosion with chlorine ion, pure and caustic water). Their price is much higher than that of standard alloys, but this price is justified for applications where operator safety is an essential criterion.
Nickel-based Superalloy tubes are used in aeronautics, in the chemical industry for their resistance to corrosion, in nuclear engineering and to a lesser extent in the food industry.
Machining superalloys are known to be very difficult. This difficulty arises from several factors. It is therefore important to be able to cool the cutting-edge during machining. The second factor that complicates machining operations is the hardness of the material.
2.Titanium
Titanium is an extremely useful metal for industry. It allows the manufacture of light tubes but very resistant to corrosion and extreme temperatures. Its mechanical characteristics are also advantageous. Only its cost limits its use to specific applications.
The thermal conductivity of titanium is very low; the heat dissipation is not optimal during machining. The cutting edge must be cooled properly to avoid machining faults.
3.Aluminum
Aluminium is a very widely used metal in the industry. Aluminium tubes are inexpensive, easy to shape and assemble together. They are also corrosion-resistant and lightweight, making them the materials of choice in aerospace, transportation and construction. Aluminium tubes are also widely used in the construction of pneumatic circuits.
The machining of Stainless Steel 316 Pipe is relatively easy because its hardness is very low. However, some problems due to its malleability can appear, such as chip clogging. The solution is to increase the machining speed, the depth of cut and the feed rate. Tube deformation during machining can also occur if the machining machine, and especially its chuck, is not suitable.