Based on the types of pipes and tubes the line pipe suppliers manufacture, you need to choose the materials for the pipes. You must follow the specific standards and codes while choosing the materials. Different materials have different stress capacities, design rules, temperature-withstanding capacities, etc.
Each material has its benefits that determine why the users choose certain materials. However, before choosing the materials, you should know how to choose them. The basics of choosing materials for pipes play a vital role as that can determine how strong and durable the pipes will be. Also, you should know the mechanical properties of the materials before choosing them. Without delay, let us dive into the selection of the materials.
The basics of selecting pipe materials:
Metallurgy engineers, popularly known as process engineers, decide the materials you should choose. Different materials have a wide range of specifications, such as AS, CS, SS, LTCS, etc. The selection procedure depends on your process, the metallurgy requirements, the licensor, temperatures, corrosion resistance, pressure resistance, etc.
As line pipe suppliers, you should also remember that the specifications include the value of the pipes users require, corrosive materials such as acid, seawater, sodium, etc., and hazardous materials such as hydrogen, phosgene, chlorine, etc. Even exposure to oxygen is essential in choosing the materials because some materials react with oxygen and oxidize, weakening the pipes and tubes.
Since metals are not mechanically strong enough to withstand pressure and temperature conditions in their raw form, you only use them with treating them. Hence, you need to heat-treat the metals and create metal alloys. Alloys enhance the metal’s properties, improving its ductility and robustness.
When you create an alloy by mixing the right proportions of alloying materials with metals, you improve its heat threshold, mechanical properties, and corrosion resistance. For example, if you use galvanization on stainless steel seamless tubes and pipes, you ensure the pipes last even longer than they ideally should. Galvanization is the process of using a zinc layer to cover the stainless steel pipes. While stainless steel is corrosion-resistant, galvanizing the metal makes it even more durable. Zinc does not react with oxygen or salt water. Therefore, you can build pipes for shipbuilding, the aviation industry, automobile exhaust systems, and many other uses where the pipes will be exposed to a corrosive environment.
Besides, alloying enhances mechanical properties, such as weldability, machinability, etc., as well.
You can also bond metal alloys with organic materials, ceramic, graphite, etc. Binding pipe materials with organic products change their mechanical properties and make them ideal for some specific uses.
Mechanical properties:
Based on the project where the users will install welded or seamless pipes, you should remember the mechanical properties of the metals. Let us quickly go through some of the properties that you should keep an eye out for:
- The elasticity of the modulus: Tension tests are used to measure the stress-to-strain ratio of the metals.
- Plastic range: Material becomes deformed even when you release the load.
- Ductility: The specimen exhibited elongation and reduced cross-sectional area before failing. Hence, you must measure the minimum diameter before failure and the maximum length before extension.
- Elastic range: When you release afterload, the material comes back to its original shape.
- Tensile strength: Tensile strength is vital as it decides how much load you can put on the metal. If the constant strain put by the load crosses the limit of the metal’s capacity, it starts thinning, losing its elongation capability, and results in failure.
- Hardness: Line pipe suppliers use Rockwell or Brinell Hardness Test to ensure that the pipes’ materials are hard enough to resist deformation.
- Fatigue resistance: Metal pipes develop fatigue when exposed to constant pressure, stress, and extreme temperatures. Every metal has its own fatigue threshold. You should choose fatigue-resistant materials to ensure that they do not crack or break when you extensively use them in repeated loading conditions.
- Toughness: Although you may think that toughness is the same as the hardness of the materials, there is a slight difference between the two. While hardness is the measurement of the resistance power of the materials when put under pressure, toughness is the measurement of how long the material can survive once deformation has set in.
Definition and terms of the materials:
Before you select the materials for seamless tubes and pipes, you must know some relevant terms about piping materials.
- Stabilization: Stabilization is the process of adding alloying material, such as zinc, to stop carbon-chromium precipitation and the appearance of carbides. Stabilization allows you to make metal pipes corrosion and high-temperature resistant.
- Creep strength: The term creep strength refers to the ability of the metal pipes to withstand intense pressure and stress at a raised temperature without failing.
- Reducing acids: Reducing acids is the term you use to state oxygen reduction and hydrogen buildup. In this case, you mean the buildup of hydrogen-based acids, such as hydrobromic, hydrofluoric, and hydrochloric acids.
- Brittle fracture: Sometimes, the materials may not be able to withstand pressure. As a result, the pipes may break apart without developing any deformation.
- Organic acids: As you can understand from the name, organic acids are a group of carboxyl acids that contain hydroxide. These include citric, formic, and acetic acids.
- Oxidizing acids: Oxidation is the opposite term of reducing acids. It means that oxidation is the term that refers to the metals gaining oxygen because of oxidization and losing hydrogen in the process. Examples include chromic, sulfuric, and nitric acid.
- Intergranular corrosion: Line pipe suppliers notice that metals often develop grain boundaries that result in corrosion. The reason behind the problem is the depletion of chromium because a carbide layer is formed when it reacts to carbon. Carbon is supposed to protect metal pipes from corrosion. However, when carbon reacts with chromium, it becomes less effective. Reducing acids, organic acids, and oxidizing acids cause the reaction.
- Stress corrosion cracking: Stress corrosion occurs when the metal pipes develop cracks due to both chemical and tensile stress corrosion. You may also notice stress corrosion because of the solution environment, metal properties, service temperature, and exposure duration.
- Hydrogen blistering: It is a common problem you notice when you use steel pipes in low temperatures. You will only notice an atomic diffusion of hydrogen into the steel pipes if you use seamless pipes. As hydrogen stays inside the metal as non-metallic inclusion, it bulges with time and causes blistering.
- Oxidation: Oxidation is popularly known as scaling. When the metal pipes react with oxygen present in the air and form oxide, you call it oxidation.
Common pipe materials for line pipe suppliers:
Metallic pipes are the most common choice for many industries. Even though choosing metallic materials can be challenging, metallic pipes are more robust, long-lasting, withstand extreme temperatures, and work even under stress. In addition, by following proper preventive methods, you can prevent oxidation, hydrogen blistering, brittle fracture, and other problems.
On the contrary, if you use alternate cheaper materials, you may save money initially. But, eventually, it may incur losses because industries do not invest in low-quality pipes.
