Seamless Pipe Raw Material Selection

Seamless pipe (SMLS pipe), as an important material widely used in the industrial field, its performance and quality are directly affected by the raw materials. Therefore, selecting appropriate raw materials and ensuring their high quality are of vital significance to the production of high-quality seamless steel pipes.

Main raw materials of seamless pipe:

The main raw material of seamless pipes is steel, which can be divided into several categories such as carbon steel, stainless steel, and alloy steel. The chemical composition, mechanical properties and smelting methods of these steels will affect the final performance of seamless steel pipes.

1. Carbon steel seamless pipe

Carbon steel is one of the main raw materials for seamless steel pipes. Its chemical composition is mainly composed of carbon, silicon, manganese, phosphorus and sulfur. Carbon steel has high purity, good toughness and weldability, and relatively low price, so it is widely used in general industrial applications. Carbon steel can be divided into low carbon steel, medium carbon steel and high carbon steel according to different carbon content. This type of pipe is often used in fields such as fluid transportation, building structures, and machinery manufacturing.

① Low carbon steel (carbon content less than 0.25%): Low carbon steel seamless pipe has good toughness and plasticity and is easy to process. However, low carbon steel has low strength and hardness and is not suitable for use as mechanical parts.
② Medium carbon steel (carbon content between 0.25% and 0.6%): Medium carbon steel pipes have higher hardness and strength and are suitable for making mechanical parts with higher strength requirements.
③High carbon steel (carbon content greater than 0.6%): High carbon steel has high hardness and strength, but poor toughness and plasticity, and is easy to break.

2. Stainless steel seamless pipe
Stainless steel seamless pipes are made of stainless steel and have good corrosion resistance and aesthetics. Stainless steel seamless steel pipes can be divided into martensite, austenite, ferrite and duplex stainless steel seamless steel pipes according to their organizational states, with different performance characteristics, and is widely used in petroleum, chemical, medical and food industries. Stainless steel material can also resist high temperature and high pressure, ensuring normal operation in various complex environments.

3. Alloy steel seamless pipe

Alloy steel adds a small amount of alloying elements, such as chromium, nickel, tungsten, molybdenum, etc., to carbon steel to improve its performance. Alloy steel seamless steel pipes have higher strength, heat resistance, corrosion resistance and wear resistance, and are suitable for manufacturing equipment and pipelines in high temperature, high pressure and corrosive environments, such as automotive, aviation and energy industries. There are various types of alloy steel, such as chromium-molybdenum alloy steel.

4. Copper and copper alloy seamless pipe
Copper and copper alloy seamless pipes are known for their good electrical conductivity, thermal conductivity and corrosion resistance. They are often used to make heat exchangers, condensers and water supply systems. In addition, copper pipes are also widely used in refrigeration and air conditioning systems.

In summary, seamless pipes are made of a variety of materials, including stainless steel, carbon steel, alloy steel, copper and copper alloys. Each of these materials has its own characteristics, and it is crucial to choose the right seamless pipe material according to the specific application scenario and needs. Stainless steel seamless pipes are corrosion-resistant and high-strength, suitable for a variety of industries; carbon steel seamless pipes are low-cost and widely used in fluid transportation and machinery manufacturing; alloy steel seamless pipes are high-temperature and corrosion-resistant, suitable for high-pressure and high-temperature environments; copper and copper alloy seamless pipes have good electrical and thermal conductivity, and are often used in the manufacture of heat exchangers and water supply systems.

How to choose high-quality seamless pipe raw materials?

Selecting high-quality raw materials is the key to producing high-quality seamless steel pipes. Here are a few strategies for choosing high-quality raw materials:

1. Understand the sources and suppliers of raw materials
Choosing suppliers with good reputation and strong technical strength can ensure the quality and reliability of raw materials. At the same time, understanding the source and production process of raw materials can help to better control the quality of raw materials.

2. Check the chemical composition and mechanical properties of raw materials
The chemical composition and mechanical properties of raw materials are tested to ensure that they comply with national standards and relevant industry regulations. In particular, attention should be paid to the content of harmful elements such as sulfur and phosphorus, as well as key indicators such as tensile strength, yield strength, and elongation.

3. Consider the smelting method and delivery status of raw materials
Smelting methods and delivery status also have an important impact on the quality and performance of raw materials. For example, electric furnace steel and converter steel may have differences in chemical composition and mechanical properties, and the appropriate smelting method needs to be selected based on specific needs. At the same time, the delivery status of raw materials also needs to be considered. Different delivery statuses such as hot rolling and cold rolling will have an impact on the performance of raw materials.

4. Strictly control the inspection and testing of raw materials
Strict inspection and testing of raw materials is an important means to ensure the quality of raw materials. Raw materials can be comprehensively tested and evaluated through ultrasonic testing, metallographic analysis and other methods to ensure that their quality and performance meet requirements.

Seamless pipe manufacturing process:

Seamless steel pipes are made by perforating steel ingots or solid tube blanks, hot rolling, cold rolling or cold drawing. Specifically, the production process of seamless steel pipes includes the following steps:

a. Raw material preparation‌: Use steel ingots or solid tube blanks as raw materials.
‌b. Perforation‌: The raw material is perforated through a perforator to form a capillary tube.
‌c. Heat treatment‌: After hot rolling, cold rolling or cold drawing, the capillary pipe is further processed to obtain the required seamless steel pipe.

According to different uses and production processes, seamless steel pipes can be divided into hot-rolled seamless steel pipes, cold-rolled (cold-rolled) seamless steel pipes and extruded seamless steel pipes. In addition, alloy seamless steel pipes are based on ordinary seamless steel pipes and add various alloy elements to improve the performance of the steel to meet the needs of specific industries, such as the high-temperature and high-pressure working environment requirements of power, boiler tube and other industries.

(1) Hot rolled seamless pipe
Hot rolled seamless pipes are generally produced on automatic pipe rolling units. After the solid tube blank is inspected and surface defects removed, it is cut into the required length, with the perforated end of the tube blank as the center, and then sent to the heating furnace for heating and perforation on the punching machine. It continues to rotate and advance during the piercing process. Under the action of the rollers and the ends, the tube blank gradually becomes hollow, which is called gross tube. Then it is sent to the automatic tube rolling machine to continue rolling. Finally, the wall thickness is leveled by a leveling machine, and the diameter is determined by a sizing machine to meet the specification requirements. Using a continuous pipe rolling unit to produce hot-rolled seamless steel pipes is a relatively advanced method.

(2) Cold rolled pipe or cold drawn pipe
If you want to obtain seamless pipes with smaller size and better quality, you must use cold rolling, cold drawing or a combination of both.

Cold rolling and cold drawing are two different processing methods, both of which can be used to produce seamless pipes with smaller sizes and better quality. Cold rolling is usually carried out on a two-roll mill, and the steel pipe is rolled in an annular pass composed of a variable cross-section circular groove and a fixed conical head. This method can improve the mechanical properties of the steel pipe through plastic deformation without changing the chemical composition of the steel pipe, making it more precise in size and better in surface quality. Cold drawing is usually carried out on a 0.5-100T single-chain or double-chain cold drawing machine, using hot-rolled seamless steel pipes or welded steel pipes as blanks to produce steel pipes and small-diameter steel pipes with little change in wall thickness. The cold drawing process can make the dimensions of the steel pipe more precise, and can also improve the internal structure and surface quality of the steel pipe.

The combination of cold rolling and cold drawing can further refine the size and improve the quality of steel pipes. This method is usually used to produce seamless pipes with smaller sizes and higher precision requirements, such as instrument pipes, precision machinery pipes, etc. Through the combination of cold rolling and cold drawing, not only can smaller seamless pipes be obtained, but its mechanical properties and service life can also be significantly improved to meet higher standard application requirements.

(3) Extruded tube
In the extrusion method, the heated tube blank is placed in a closed extrusion cylinder, and the perforated rod and the extrusion rod move together to make the extruded part extruded from the smaller die hole. This method can produce steel pipes with smaller diameters. 

Conclusion:

The main raw material of seamless pipes is solid tube blanks, which include carbon steel, stainless steel, and alloy steel. Choosing high-quality raw materials is the key to producing high-quality seamless steel pipes. By understanding the sources and suppliers of raw materials, checking their chemical composition and mechanical properties, considering smelting methods and delivery status, and strictly controlling inspection and testing, we can ensure that the raw material quality and performance of seamless steel pipes meet the requirements, thereby producing High quality seamless steel pipe products.

Read more: Seamless vs Welded Pipe or American Standard Seamless Steel Pipe