Hot Rolled Seamless Steel Tube

Hot rolled seamless steel tube: hot rolling is related to the cold drawn, hot rolling is performed above the recrystallization temperature of the rolling. 

Hot-rolled Seamless Steel Tube Advantages: 

1. High Pressure Capacity, Safe and Reliable
No Welds: This is the core advantage. Welds are often the weak link in pipelines. Hot-rolled seamless steel pipes are weld-free throughout, resulting in uniform pressure-bearing capacity in all directions. They can withstand extremely high internal pressures and are suitable for critical high-pressure systems (such as power plant boilers and petrochemicals).

2. Improved Material Properties
High-Temperature Hot-Rolled Microstructure: The hot rolling process breaks down the ingot cast structure, refines the steel grains, eliminates microstructural defects, and improves mechanical properties (such as yield strength and tensile strength). This improvement is primarily achieved along the rolling direction, making the steel less isotropic to a certain extent. Air bubbles, cracks, and loose areas formed during casting can also be welded together under high temperature and pressure.

Suitable for Harsh Working Conditions: They can withstand complex stresses such as impact, vibration, and alternating loads, making them suitable for harsh working environments.

3. Reduced Energy Consumption
High thermoplasticity and low deformation resistance reduce energy consumption. ‌

4. Improved Efficiency, Relatively Low Cost‌
Using large ingots and high reduction rolling, production efficiency is improved and continuous automated production is achieved.

Compared to cold drawing/cold rolling, hot rolling has a shorter production process, higher output, and higher production efficiency. Therefore, for the same material and specifications, the production cost of hot-rolled seamless pipe is lower than that of cold-drawn/cold-rolled seamless pipe, making it cost-effective for bulk purchases and large-scale projects.

5. Wide Specification Range, Capable of Producing Large Diameter, Thick-Walled Pipes
Wide Diameter Range: OD typically starts at 32mm and can reach over 1000mm, a range difficult to achieve with cold-drawn pipes.
Wide Wall Thickness Range: Thick and ultra-thick wall seamless steel pipes can be produced, reaching thicknesses of tens or even hundreds of millimeters. They are commonly used in large mechanical structures, nuclear power plant main piping, and other applications.

6. Wide Application Range
Various Materials: Hot rolling can produce a variety of materials, including carbon steel, alloy steel, and stainless steel.
Strong Temperature Resistance: Due to its dense structure and uniform properties, it maintains stable performance in both high and low temperature environments.

Hot-rolled Seamless Steel Tube Disadvantages: 

Disadvantages of Hot Rolling Process:

1. After hot rolling, the steel inside the non-metallic inclusions (mainly sulphide and oxide, and silicates) is pressed into the sheet, delamination (interlayer) phenomenon. Layered in the thickness direction of the steel tension performance deteriorated significantly, and there may be an interlayer tear weld shrinkage. Weld local strain-induced contraction of the yield point strain often reach several times larger than the load caused by the strain.

2. Residual stresses caused by uneven cooling. Residual stresses in the absence of external force from the internal equilibrium of stress, both hot-rolled steel section such various residual stress, the greater the cross-sectional size generally of steel, the residual stress is larger. Although the residual stress from equilibrium, but still has some influence on the performance of the steel members under loads. Terms such as deformation, stability, anti-fatigue effects may adversely. 

3. Hot-rolled steel products, poor control of the thickness and width of the edge in this respect. We are familiar with thermal expansion and contraction, since the beginning of the hot rolling out even the length, thickness are standard, and finally cooled or there will be some negative difference, this negative difference edge width wider, thicker the more obvious manifestations. So for large steel for steel edge width, thickness, length, angle, and no law requires very precise edges. 

Disadvantages of Hot Rolling Seamless Pipe Finishes:

1. Poor Dimensional Accuracy and Surface Finish
Wide Dimensional Tolerances: Compared to cold-drawn pipe, the control accuracy of the outer diameter and wall thickness is lower, and the tolerance range is wider.
Surface Quality: The surface is relatively rough with scale and may contain pitting and slight pitting. It is generally not suitable for direct use in applications requiring high surface quality.

2. Poor Wall Thickness Uniformity
This is a common problem with hot-rolled seamless pipe. Due to the inherent characteristics of the piercing and rolling processes, the wall thickness uniformity is generally inferior to that of high-quality welded pipes and cold-drawn pipes, and some eccentricity may occur.

3. Limited Cut Lengths

Due to the hot-rolling process, the length of a single steel pipe is generally not as long as that of continuously produced welded pipe.

4. Limited Minimum Diameter and Wall Thickness

It cannot produce small diameters (e.g., < Φ25mm) and thin-walled pipes like cold-drawn pipe. The minimum diameter and wall thickness limits for production are relatively high.

5. Subsequent processing may require oxide scale removal.
The oxide scale formed on the surface after hot rolling requires removal through processes such as sandblasting and pickling, increasing the cost and steps of subsequent processing.

Hot-rolled Seamless Steel Tube Manufacturing Process: 

Round tube perforation → heating → three-roll rolling, rolling or extrusion → detached → sizing (or reducing) → cooling → straightening → hydrostatic test (or testing) → mark → storage

Application areas of hot-rolled seamless tubes and how to choose:

1. Petroleum field: Hot-rolled seamless steel tubes can be used as oil well riser pipes, oil pipes, oil casings and casings, etc. They can withstand greater oil pressure and the high-temperature and high-pressure environment in the oil circuit.
2. Chemical industry: Hot-rolled seamless steel tubes can also be used in chemical pipelines, furnace tubes, containers and storage tanks, etc. Has good corrosion resistance.
3. Aviation and aerospace fields: Hot-rolled seamless steel tubes are commonly used in the aviation and aerospace fields to manufacture components such as engines and tires.
4. Machinery manufacturing field: Hot-rolled seamless steel tubes can also be used as hydraulic pipes, transmission shafts and other components of machines. Due to its high strength, high precision and high pressure resistance, it can effectively improve the working efficiency and service life of machinery and equipment.

Hot-rolled seamless pipes are widely used in oil and gas transportation, chemical industry, aerospace, machinery and equipment manufacturing, building decoration and other fields. When choosing steel pipes, you should choose according to its use environment and characteristics: in areas where higher strength is required, hot-rolled seamless tubes are a good choice. If a higher surface finish is required, you can choose cold-drawn seamless tubes or cold-drawn welded pipes.

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