The Importance of Precise Wall Thickness Control
Date:2025-10-21
1. Why is Wall Thickness Control So Important?
The quality of wall thickness control directly determines the fate of steel pipes.
Safety (Pressure Capacity): For pressure-bearing pipes transporting media such as oil and gas, wall thickness is crucial for resisting internal pressure. Excessively thin wall thickness can directly lead to insufficient pressure-bearing capacity, causing catastrophic accidents such as pipe bursts and leaks.
Economics (Cost and Efficiency):
Negative Wall Thickness Deviation: While ensuring minimum wall thickness, precisely controlling negative wall thickness deviation (i.e., actual wall thickness slightly below nominal wall thickness but still within the standard range) can save significant amounts of steel, reduce raw material costs, and achieve "weight reduction and efficiency improvement."
Positive Wall Thickness Deviation: Excessive positive wall thickness deviation means material waste, increasing costs and causing the unit weight of the steel pipe to exceed the standard, impacting subsequent construction and transportation.
Process Stability and Service Life: Steel pipes with uneven wall thickness will experience stress concentration when subjected to stress, particularly at the thinnest wall thickness. This significantly reduces fatigue life and accelerates corrosion and damage to the pipe body.
Meeting Standards and Customer Requirements: Various domestic and international standards (such as API, ASTM, and GB) have strict regulations for wall thickness tolerances for steel pipes. Precise wall thickness control is crucial for meeting product standards and securing market access.
II. Key Factors Affecting Steel Pipe Wall Thickness Uniformity
Wall thickness unevenness is a systemic issue, the root cause of which runs throughout the entire production process.
Pipe Quality: Center segregation, shrinkage cavities, or internal cracks in continuously cast billets are amplified during subsequent piercing and rolling, leading to uneven wall thickness.
Piercing: This is the core step in hot-rolled seamless steel pipe production. The position and wear of the piercing plug, as well as roll adjustment parameters (such as feed angle and rolling angle), directly determine the initial rough pipe wall thickness distribution. Force imbalance is the primary cause of symmetrical "ear-shaped" wall thickness unevenness.
Rolling Process: In equipment such as continuous tube mills and sizing mills, the roll pass design, roll gap accuracy, rolling center alignment, and speed matching between stands all have a decisive impact on final wall thickness accuracy.
Equipment Condition: Equipment factors such as mill housing stiffness, roll and mandrel wear, and bearing clearance can all introduce unpredictable thickness fluctuations.
Temperature Uniformity: Uneven temperatures within the heating furnace lead to varying resistance to deformation during rolling, causing the material to flow toward softer (higher) wall areas, resulting in wall thickness variations.
