During the design phase, the characteristics of the materials must be carefully studied and fixed to avoid any complications during their use while avoiding unnecessary costs.
This is even truer when it comes to choosing a material for a tube. Certain tubes are, in fact, subjected to strong mechanical, thermal or even chemical stresses depending on the type of fluid they transport, its pressure and its temperature.
The Carbon steel pipe from which the tube was made will have an influence on all manufacturing operations, including machining operations. The machinability of a tube depends directly on the material in which it was made, and for each material, special precautions must be taken to guarantee quality machining.
Machining is a common operation when preparing for welding, for example, where the end of the tube must be machined at precise angles to allow the weld to penetrate the material throughout the thickness of the tube.
1. Standard Steel
Standard steel tubes are the most widely used because of their low cost and their mechanical qualities which are suitable for a large number of applications. Steel tubes are strong, durable and deformable. They can therefore be used for applications involving large variations in temperature or pressure. This type of tube is also widely used when shocks or vibrations can affect the pipeline. a106 grade b are quite simple to make and can be bent or cut quite easily.
Steel pipes are, however, very susceptible to corrosion if no treatment is applied. A common treatment against corrosion is galvanizing. This involves covering the steel tube with a zinc coating. This zinc coating will oxidize instead of the steel it protects, but very slowly.
The machining of low A335 P11, that is to say with low carbon content, does not pose any particular machining problems. As the carbon content increases, material properties such as hardness or mechanical strength tend to be significantly improved. This therefore also has a strong influence on the mach inability which tends to be more complicated with steels containing a high carbon content.
alloy steel pipe is alloy steel with a high content of Chromium (9%) and Molybdenum (1%). The addition of Chromium makes it possible to increase the mechanical resistance at high temperature as well as the corrosion resistance. Molybdenum improves resistance to deformation. Small amounts of Nickel and Manganese improve the hardness of the material. The P91 is very sensitive to variations in its microstructure which can occur during excessive heating. These variations in microstructure tend to weaken the material. This is why cold machining is often preferred for cutting this type of material.
This means that the last stages of the superheated and the pipes supplying the steam from the turbine must withstand these extreme conditions. A material with high mechanical strength that does not deteriorate over time like P91 is therefore necessary.
A Duplex stainless steel consists of a chrome stainless steel and addition of nickel. The matrix contains both ferrite and austenite hence the name Duplex. This alloy has been designed to provide corrosion resistance and tensile strength.