What is Black Steel Pipe

Black steel pipe is uncoated steel, also known as black steel. The dark color of this steel pipe comes from the iron oxide that forms on its surface during the manufacturing process. When the steel pipe is forged, a black oxide scale forms on its surface, giving this type of pipe a specific finish. The main uses of black steel pipe include the delivery of propane or natural gas to residential and commercial buildings. In addition, welded steel pipe for low-pressure fluid delivery (GB/T3091-2008) is also called general welded pipe or commonly known as black pipe. It is a welded steel pipe used for conveying generally lower pressure fluids such as water, gas, air, oil and heating steam and other uses.

Characteristics of black pipes

Black pipes have the following characteristics:

1. Corrosion resistance: Black steel pipes will generate black iron oxide on the surface due to oxidation reaction, forming a protective layer that is not easy to fall off, with excellent corrosion resistance and stronger ability to withstand chemical action;

2. High strength: Black steel pipes are processed by hot rolling, cold drawing and other processes, with smooth surface, high strength, strong pressure resistance, can withstand greater pressure, and strong bending resistance, so they are suitable for occasions with heavy loads;

3. Good processability: The surface is black. Since the material of black steel pipes is relatively soft and has good processability, it can be subjected to a variety of surface treatments, and has better aesthetics than other steel pipes;

4. It has good mechanical properties and stronger tensile, compressive and bending resistance.

Types and uses of black steel pipes

1. Welded steel pipes

Welded steel pipes are pipes formed and welded by steel strips or steel plates. Its advantages are low production cost, easy customization by manufacturers, and widely used in construction, bridges, ships, machinery manufacturing and other fields. But at the same time, those steel pipes that use welding forming technology are prone to cracks, cracking and blockage at the joints, and are also prone to rust and corrosion.

2. Seamless steel pipe

Seamless steel pipe is produced by heating, perforating, rolling and other processes of steel billet, and has very good seamless performance. Seamless steel pipe has the advantages of high tensile strength and good compressive strength, and has a wide range of uses in water conservancy, petroleum, natural gas and other industries. In addition, seamless steel pipe can also be made into pipes for high-pressure boilers, pipes for fertilizer equipment, pipes for oil cracking, pipes for automobile manufacturing, etc.

3. Galvanized steel pipe

Galvanized steel pipe is a layer of zinc plated on the surface of ordinary steel pipe, which has good anti-corrosion ability. Galvanized steel pipe is commonly used in construction, chemical industry, electric power and other industries, and is widely used for conveying various media such as gas, water, oil, etc. In addition, galvanized steel pipe can also be used in automobile manufacturing, fire fighting equipment, HVAC equipment and other fields.

Black steel pipe is a common pipe material, and different types of black steel pipes have their own advantages and disadvantages during use. By understanding the characteristics of various types of steel pipes, you can more accurately choose the right pipe material to meet different needs.

Application fields of black pipes

Black pipes are widely used in machinery, construction, engineering, petrochemical, chemical, metallurgy, shipbuilding, electricity, environmental protection and other fields, and their application range covers steel components in various fields. For example, supporting structures of columns, beams, and steel plates in buildings; pipelines for transporting liquids and gases in petrochemical, chemical and other industries, as well as equipment used to make steam boilers, pressure vessels, coolers, heat exchangers, etc.; in the field of mechanical processing, black steel pipe fittings are usually used to make bearings, tires, etc.

Differences between black pipes and other steel pipes

1. Color: The surface of black steel pipe fittings is often covered with black iron oxide formed after oxidation, while other steel pipe fittings are generally silver-white or yellow, with different treatment methods such as galvanizing and spraying;

2. Toughness: The toughness of black steel pipe fittings is relatively good, while other steel pipe fittings are generally brittle.

3. Usage scenarios: Black steel pipe fittings are suitable for various construction and mechanical fields, while other steel pipe fittings have more subdivided application scenarios.

4. Manufacturing process: Black pipes are usually made by welding, while other steel pipes may use different manufacturing processes.

For example: The main difference between black steel pipe and galvanized steel pipe is whether it is coated. Galvanized steel pipe is steel covered with a layer of zinc metal. By immersing the steel in a molten zinc bath, a strong and uniform isolation coating is ensured, making the steel pipe more corrosion-resistant. Black steel pipe, on the other hand, remains in its original, uncoated state, and its surface is black due to oxidation.

Material introduction

Black steel pipe fittings are usually made of carbon structural steel materials with a high carbon content, also known as ordinary carbon steel pipe fittings. This material has the characteristics of high strength and good toughness, and is suitable for use in various mechanical equipment, construction projects, oil and gas transportation and other fields. Common black steel pipe fittings are made of Q195, Q235, Q345, etc.

How to prevent cracks in seamless black steel pipes

High-precision seamless black steel pipes generally improve the properties of the material by adding alloys to the metal. After cold drawing, the seamless black steel pipe needs to be subjected to stress relief annealing to eliminate the residual stress of the material, improve the material structure, and improve the material. Plasticity, thereby preventing the occurrence of fracture failure of seamless black steel pipes.

At present, the material of stainless steel seamless steel pipe in my country is ordinary 45# or 20# steel 27SiMn steel, which improves the metal strength through cold drawing deformation; however, it is at the expense of sacrificing the plasticity and toughness of the metal. High precision cold drawn seamless steel pipe is based on its high dimensional accuracy and high strength properties. It is necessary to ensure that the deformation amount is within a certain range in order to maximize the performance of the material and reduce the material. Negative impact.

The deformation of the seamless black steel pipe is too small to meet the requirements of surface finish and dimensional accuracy, and the strength index of the components cannot be achieved; A fibrous structure is formed, and the metal will have significant anisotropy. The axial direction of the cold-drawn seamless steel pipe is parallel to the elongation direction of the grain, and the strength increases; the radial direction of the cold-drawn seamless steel pipe is perpendicular to the elongation direction of the grain, and the strength decreases instead. The maximum stress of the hydraulic cylinder exists in the seamless steel pipe. The radial direction of the steel pipe, so the excessive deformation is not conducive to the performance of the cold drawn pipe.

Conclusion

In general, black pipe, as a widely used steel component, has many characteristics and advantages. I hope that through the introduction of this article, readers can better understand the relevant knowledge of black pipes and provide reference for their application in actual work and life.

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