An Overview of Five Common Tubes: Properties, Applications and Key Parameters

Tubes are essential components in industrial production, infrastructure construction, high-end manufacturing, and many other fields. Their material, structure, and performance directly determine project quality and operational safety. Among numerous tube types, seamless steel tube, stainless steel tube, hydraulic steel tube, alloy steel tube, and aluminum tube stand out due to their unique advantages, dominating a large share of the application market. This article comprehensively popularizes these five common tubes from the perspectives of definition, core properties, application scenarios, and key parameters, helping readers understand their applicable logic and selection criteria.

I. Definitions and Core Classifications of the Five Tubes

Tubes are typically classified based on material, forming process, and purpose. Significant differences in production processes between different types of tubes directly lead to variations in their performance. The following are the precise definitions and core classifications of the five tubes, clarifying their essential attributes and scope boundaries.

1.1Seamless Steel Tube

 
Seamless steel tube refers to a steel tube produced by hot rolling, cold rolling, or cold drawing directly from a solid billet without welding seams. Its core advantage lies in a uniform overall structure, free from strength weak points caused by welding defects. According to the production process, it can be divided into hot-rolled seamless steel tube and cold-drawn (cold-rolled) seamless steel tube: hot-rolled seamless steel tube is manufactured by high-temperature rolling, with a wide diameter range (usually Φ25-630mm), suitable for medium and low-pressure working conditions; cold-drawn seamless steel tube undergoes low-temperature precision drawing, featuring higher dimensional accuracy (tolerance controllable within ±0.05mm) and low surface roughness, commonly used in high-pressure and high-precision scenarios.

1.2 Stainless Steel Tube

Stainless steel tube is made of stainless steel, with excellent corrosion resistance as its core feature. This corrosion resistance originates from the dense chromium oxide passive film formed on the surface of stainless steel. According to the material composition, the mainstream classifications are austenitic stainless steel tubes (such as 304 and 316 grades), ferritic stainless steel tubes (such as 430 grade), and martensitic stainless steel tubes (such as 410 grade). Among them, austenitic stainless steel tubes are the most widely used due to their good toughness, weldability, and corrosion resistance; martensitic stainless steel tubes are often used in scenarios requiring both corrosion resistance and load-bearing capacity due to their certain strength and wear resistance.

1.3 Hydraulic Steel Tube

Hydraulic steel tube is a special conveying tube for hydraulic systems, mainly responsible for the transmission of hydraulic oil and pressure. It has extremely high requirements for the pressure resistance, dimensional accuracy, and inner wall smoothness of the tube. According to the forming process, it can be divided into hydraulic seamless steel tube and hydraulic welded steel tube. However, due to the possible uneven pressure transmission caused by welding seams, hydraulic seamless steel tube is more commonly used. Its material is usually high-quality carbon steel or low-alloy steel. After precision processing, the inner wall roughness can be as low as Ra0.4μm or less, ensuring the smooth flow of hydraulic oil and reducing pressure loss.

1.4 Alloy Steel Tube

Alloy steel tube is a steel tube made by adding one or more alloying elements (such as chromium, molybdenum, nickel, vanadium, etc.) to carbon steel. The purpose is to improve the strength, toughness, temperature resistance, or corrosion resistance of the steel. According to the content of alloying elements and application, it can be divided into low-alloy steel tubes (total alloying element content < 5%), medium-alloy steel tubes (5%-10%), and high-alloy steel tubes (> 10%). Different combinations of alloying elements endow the tubes with different properties. For example, chromium-molybdenum alloy steel tubes have excellent high-temperature resistance, while nickel-chromium alloy steel tubes have stronger corrosion resistance.

1.5 Aluminum Tube

Aluminum tube is made of pure aluminum or aluminum alloy through extrusion, rolling, and other processes. Its core advantages are low density (2.7g/cm³, only 1/3 of steel), good thermal conductivity, corrosion resistance, and easy processing. According to the material, it can be divided into pure aluminum tubes (such as 1060 and 1050 grades) and aluminum alloy tubes (such as 6061 and 6063 grades); according to the forming process, it can be divided into extruded aluminum tubes, drawn aluminum tubes, and rolled aluminum tubes. Pure aluminum tubes are suitable for low-pressure and corrosion-resistant scenarios, while aluminum alloy tubes are often used in structures requiring both lightweight and load-bearing capacity due to their higher strength.

II. Core Properties and Typical Application Scenarios of the Five Tubes

The differences in properties of the five tubes determine the subdivision of their application fields. Understanding their core properties and applicable scenarios is the key to achieving accurate selection. The following will decompose the core performance of each tube one by one and illustrate their applicable ranges with practical application cases.

2.1 Seamless Steel Tube: Excellent Strength for Medium and High-Pressure Conditions

The core properties of seamless steel tube are high tensile strength (hot-rolled seamless steel tube: ≥410MPa; cold-drawn seamless steel tube: ≥510MPa), dense structure, and high pressure resistance. It is widely used in oil and gas transmission pipelines, boiler tubes, and mechanical structural parts. For example, in oilfield exploitation, hot-rolled seamless steel tubes are used to transport crude oil and natural gas due to their ability to withstand high pressure and harsh underground environments; cold-drawn seamless steel tubes are used in the manufacturing of engine cylinders and hydraulic system components due to their high precision.

2.2 Stainless Steel Tube: Corrosion Resistance for Harsh Environments

Stainless steel tube's biggest advantage is corrosion resistance, which can resist the erosion of acids, alkalis, salts, and other corrosive media. 304 stainless steel tubes are commonly used in food processing, medical equipment, and architectural decoration fields. For example, in food factories, 304 stainless steel tubes are used to transport food raw materials and cleaning agents due to their non-toxicity and corrosion resistance; 316 stainless steel tubes, with better corrosion resistance than 304, are widely used in marine engineering and chemical industry to withstand the corrosion of seawater and chemical reagents.

2.3 Hydraulic Steel Tube: High Precision for Efficient Hydraulic Transmission

Hydraulic steel tube is designed for hydraulic systems, requiring high pressure resistance (usually able to withstand pressure above 31.5MPa), high dimensional accuracy, and smooth inner wall. It is the core component of hydraulic systems in construction machinery, industrial machinery, and aerospace fields. For example, in excavators, hydraulic steel tubes transmit hydraulic oil to drive the movement of arms and buckets; in aircraft hydraulic systems, precision hydraulic steel tubes ensure the stable operation of landing gear and control systems.

2.4 Alloy Steel Tube: Customizable Properties for Special Working Conditions

 
Alloy steel tube's performance can be customized by adjusting the type and content of alloying elements, making it suitable for special working conditions such as high temperature, high pressure, and strong corrosion. Chromium-molybdenum alloy steel tubes are widely used in thermal power plants and petrochemical plants to transport high-temperature and high-pressure steam and oil; nickel-chromium alloy steel tubes are used in nuclear power plants due to their excellent radiation resistance and high-temperature stability.

2.5 Aluminum Tube: Lightweight and High Thermal Conductivity for Diversified Applications

Aluminum tube's low density and good thermal conductivity make it widely used in aerospace, automotive manufacturing, and air conditioning and refrigeration fields. In aerospace, aluminum alloy tubes are used to manufacture aircraft fuselage and engine components to reduce the overall weight of the aircraft; in automotive air conditioning systems, aluminum tubes are used to transport refrigerant due to their good thermal conductivity; in architectural decoration, pure aluminum tubes are used to make handrails and decorative strips due to their corrosion resistance and beautiful appearance.

III. Key Performance Parameters Comparison of the Five Tubes

To facilitate the selection of tubes in practical applications, the following table compares the key performance parameters of the five tubes, including density, tensile strength, maximum service temperature, and corrosion resistance. The data in the table is based on common grades of each tube type, providing a reference for engineering selection.

Tube Type	Density (g/cm³)	Tensile Strength (MPa)	Maximum Service Temperature (℃)	Corrosion Resistance Level
Seamless Steel Tube (20#)	7.85	410-550	450	Medium
Stainless Steel Tube (304)	7.93	515-720	870	High
Hydraulic Steel Tube (20# Precision)	7.85	≥510	420	Medium
Alloy Steel Tube (15CrMoG)	7.80	440-640	550	High
Aluminum Tube (6061)	2.70	205-310	200	High

Note: The data in the table is for reference only. Specific parameters may vary depending on the material grade, production process, and heat treatment method. For special working conditions, it is necessary to select the appropriate tube type and grade based on professional technical specifications.

IV. Conclusion

Seamless steel tube, stainless steel tube, hydraulic steel tube, alloy steel tube, and aluminum tube each have unique performance advantages and application fields. Seamless steel tube is favored for its high strength, stainless steel tube for its corrosion resistance, hydraulic steel tube for its high precision in hydraulic transmission, alloy steel tube for its customizable properties, and aluminum tube for its lightweight and good thermal conductivity. In practical applications, the selection of tube type should comprehensively consider factors such as working pressure, temperature, corrosive environment, load-bearing requirements, and cost. By mastering the properties and parameters of these five tubes, we can better apply them to various engineering fields, ensuring the reliability and efficiency of the project.