Research on Mechanical Properties of Cold Rolled Tube Grouting Sleeve

Cold-rolled seamless steel pipe grouting sleeve, also known as a cylindrical sleeve, is a tube-like part made of seamless steel pipe, which is used to link two seamless steel pipes. The sleeve can prevent the threaded joint from being worn and damaged because of axial movement and pressure, so as to effectively prolong the service life of the pipeline. As a fastening part, the mechanical properties of the sleeve are especially important, which determines its ability to resist pressurization, vibration and aging. Through researching on materials, heat treatment, metallness and friction properties, this article expounds the mechanical properties and importance of cold-drawn seamless steel pipe grouting sleeve in the joint connection of pipe fittings.
    
Material Characteristic of the Cold-rolled Seamless Steel Pipe Grouting Sleeve
    
The selection of cold-rolled seamless steel pipe grouting sleeve material plays a decisive role in its performance. In consideration of cost, weight, corrosion and other aspects,Grade 20# carbon structural steel is usually chosen and the main content includes 0.17-0.23% of carbon, 0.35-0.60% of silicon and 0.35-0.70% of manganese. Grade 20# carbon structural steel has excellent mechanical properties, creep strength and corrosion resistance, which make it widely used in many industries.
    
Cold-rolled Seamless Steel Pipe Heat Treatment Characteristic:
The heat treatment of cold-drawn seamless steel pipe grouting sleeve is closely related to its mechanical properties. After heat treatment, the sleeve achieves the process requirements for mechanical properties, dimensions and certain environmental requirements. Generally, high-temperature normalizing and high-temperature tempering are adopted for the heat treatment of grouting sleeve. In high temperature normalizing treatment, the sleeve is heated to 860-900 ℃ and then cooled in air or oil. In high temperature tempering treatment, the sleeve is initially heated to 700-760℃, then subjected to quenching, and finally it is heated to a temperature of 200-330℃ for tempering.
    
Cold-rolled Seamless Steel Pipe Metallographic Characteristics:
Metallographic examination of the cold-drawn seamless steel pipe grouting sleeve is helpful to further understand its qualities. The higher the hardness and microstructure of the pipe, the better its mechanical properties. The hardness of Grade 20# carbon steel can reach HB270~330 during normalizing treatment, which can ensure its strong compressive strength, elasticity and impact toughness. The microstructure of 20# seamless steel consists of lath martensite, bainite and ferrite.
    
Cold-rolled Seamless Steel Pipe Friction Characteristics:
The anti-friction characteristics of cold-drawn seamless steel pipe grouting sleeve is a key metric for its performance. The grouting sleeve is usually matched with other fastening parts, such as bolts and nuts in its application; therefore, the friction between them must be considered. In order to maximize its anti-friction performance, the sleeve needs to be coated with a variety of anti-friction materials, such as oxidation resistant coatings and oil-film coatings. This will effectively improve its wear-resistance, bearing capacity and anti-corrosion ability.
    
Cold-drawn seamless steel pipe grouting sleeve is used to connect two seamless steel pipes, so it is important to understand its material, heat treatment, metallness and friction characteristics. The material of the grouting sleeve should be Grade 20# carbon structural steel for its excellent mechanical properties and corrosion resistance, and usually it need to go through high-temperature normalizing and high-temperature tempering treatments. The metallographic examination of the sleeve shows that its hardness can reach HB270~330, and its microstructure consists of lath martensite, bainite and ferrite. The friction characteristics of the sleeve needs to be improved through coating with oxidation resistant coatings and oil-film coatings in its application. Therefore, it is clear that the mechanical properties of cold-rolled seamless steel pipe grouting sleeve are incredibly important in ensuring secure pipeline connections.

---