As a professional seamless steel tube manufacturer, the hot piercing process is the primary forming procedure for hollow billets. The quality of piercing directly decides wall thickness deviation, inner surface quality, and dimensional tolerance of the rough tube. Strict tolerance control throughout hot working is essential to meet ASTM, DIN, and GB standards for high-pressure pipeline, boiler, and hydraulic tubing. Round billets for carbon steel or alloy steel will first go through strict sampling tests including chemical composition analysis and ultrasonic flaw detection to remove cracks, slag inclusions and internal porosity. The solid round bar is cut into fixed lengths by sawing equipment. For high-precision thick-wall seamless tubes, we machine a central pilot hole on the billet to reduce inner surface tearing during piercing and improve concentricity. Then the billet is evenly heated in a rotary heating furnace to the rolling temperature ranging from 1180℃ to 1250℃. Uneven local heating will inevitably result in eccentric wall thickness. The heated blank is sent into a two-roll piercing mill. Under continuous squeezing from tapered rolls, transverse tensile deformation takes place inside the metal. A plug mandrel is pushed into the center to form a hollow tubular shell known as a pierced bloom. After piercing, the hollow shell enters the continuous rolling mill, where the outer diameter is reduced and the tube wall is thinned evenly to stabilize the preliminary dimension. The tube then passes through the sizing mill to fix outer diameter and moves to the cooling bed for slow air cooling to prevent cracking caused by thermal stress. Cold straightening is used to correct bending deformation, followed by visual inspection and dimensional measurement before cold drawing and other finishing treatments. The most frequent tolerance errors during hot piercing mainly include eccentric wall thickness, out-of-round shape, inner hole scratches, outer diameter out of tolerance, as well as local folds and internal cracking. Most of these defects stem from inconsistent billet temperature, mandrel misalignment and improper roll gap setting. To keep dimensional accuracy stable, we strictly control heating uniformity and limit the temperature difference along the billet within 30℃. Excessive temperature will lead to over-tensile deformation, while insufficient heating causes metal tearing and inner folds. The rotary furnace adopts segmented temperature control to keep the metallographic structure consistent batch after batch. Operators adjust the cross angle and roll gap strictly based on wall thickness. An overlarge feed angle worsens eccentricity, whereas too small an angle fails to form a complete hollow structure. Roll clearance will be recalibrated before every production run to keep the wall thickness tolerance of hot rough tubes within ±8%. The piercing plug must maintain perfect concentricity with the billet, and mandrel deviation is the leading reason for uneven wall thickness. Boron nitride high-temperature lubricant is coated on the mandrel surface to lower friction and avoid inner hole scoring and metal adhesion. Feeding speed is also well regulated. High-speed feeding disturbs metal flow and leads to uneven wall distribution. We use low-speed stable piercing for alloy steel and thick-wall tubing to ensure consistent dimensions. Laser calipers conduct continuous online testing of outer diameter and wall thickness right after piercing, so defective hollow blooms can be eliminated timely and avoid carrying tolerance errors into the next rolling process. For carbon steel seamless pipe blanks after hot piercing, the outer diameter tolerance is controlled at ±1.0%, wall thickness tolerance between ±7% and ±10%, and straightness less than 2mm per meter. Subsequent cold drawing and fine rolling can further narrow down tolerances to produce precision seamless tubes used in machinery and pressure vessels. Every batch of pierced tube blanks will receive full inspections including visual examination for internal and external folds and cracks, multi-point wall thickness measurement, and UT nondestructive testing to find metallurgical defects. Only qualified hollow blanks can proceed to elongation rolling and finishing. Standardized hot piercing technology and precise parameter adjustment form the core competitiveness of a reliable seamless steel tube manufacturer. By managing billet quality, heating temperature, roll parameters and mandrel concentricity, we greatly reduce wall eccentricity and surface defects. Stable piercing quality cuts rejection rates and ensures finished pipes fully comply with international industrial standards for overseas engineering procurement.