Difference between mild steel pipe and carbon steel pipe

Difference between mild steel pipe and carbon steel pipe refers to the machining surface has a smaller spacing and small valley roughness. 

Two peaks or troughs which the distance between the two (the pitch) is small (at 1mm or less), it is difficult to distinguish with the naked eye, so it belongs to the micro geometry errors. Smaller the surface roughness, the surface is more smooth. The size of the surface roughness on the performance of mechanical parts have a great impact.

Mild Steel

Mild steel is the type of carbon steel where it contains very low amounts of carbon. Approximately, it is 0.16–0.29% by weight. This steel is very cheap and most commonly used. It is malleable and ductile but has low tensile strength. Mild carbon cannot be hardened by heat treatment. 

Carbon steel

Carbon steel is used to denote steel with carbon as the main alloying element. In carbon steel, the properties are mainly defined by the amount of carbon it has. For this alloy, the amounts of other alloying elements like chromium, manganese, cobalt, tungsten are not defined. There are four types of carbon steel. This categorization is based on the carbon content. Mild and low carbon steels contain very low carbon percentages. There are three other types of carbon steel as medium carbon steel, high carbon steel and ultra high carbon steel. In the higher carbon steels, the carbon level varies between 0.30–1.70 % by weight. Medium carbon steel has 0.30–0.59% carbon content whereas the high steel has 0.6-0.99%. Ultra high carbon steel has 1.0-2.0% of carbon content. They can undergo heat treatment successfully. Therefore, normally these are very strong and hard, but ductility can be low. 



Mild steel has very low carbon percentage compared to other carbon steel. Mild steel has high ductility, and it is malleable, whereas other carbon steel types have low ductility. Mild carbon cannot be hardened by heat treatment, but other types of carbon steel can be hardened by heat treatment. Mild steel is less strong and harder than other carbon steel types. Steel surface roughness Ra is usually expressed.



Pipe surface roughness is mainly manifested in the following aspects:

1. Surface roughness of the wear parts. The rougher the surface, with the effective contact surface area between the smaller, the greater the pressure, the faster the wear.
2. the nature of the surface roughness with stability. For clearance fit, the rougher the surface, the more easy to wear, so that the work process gap increases; against interference fit, because the assembly will squeeze micro convex peak level, reducing the actual effective interference, reduce the connection strength.
3. Surface roughness fatigue strength of parts. The rough parts of the surface of the trough there is a big, they look like sharp as gaps and cracks, the stress concentration is very sensitive, thus affecting the fatigue strength of parts.
4. Surface roughness of parts corrosion resistance. Rough surface, easy to corrosive gas or liquid through the valley penetrate microscopic surface to the metal inner layer, resulting in surface corrosion.
5. Surface roughness of the sealing parts. Rough surfaces can tightly fit between the gas or liquid through the gap between the contact surface leakage.
6. surface roughness of parts contact stiffness. Parts with surface contact stiffness is under external force, the ability to resist deformation of the contact. The stiffness of the machine depends largely on the contact stiffness between the various parts.
7. affecting the measurement accuracy of parts. Parts measured surface and measuring tools to measure surface roughness will directly affect the measurement accuracy, especially in precision measurement. In addition, the surface roughness of the part plated coating, thermal resistance and contact resistance, and radiation reflectance properties, resistance to the flow of liquids and gases, the flow of current conductor surface and so have different degrees.

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