Capillary rolling is the main deformation process of seamless steel tube production. Its function is to make the wall thickness of the capillary close to or reach the thickness of the finished tube wall, and eliminate the non-uniform thickness of the longitudinal wall produced by the capillary during the perforation process. The surface quality of the inner and outer parts of the waste water pipe controls the outer diameter and roundness of the waste water pipe. The hollow capillary tube is rolled into a waste liquid tube close to the final size.


1. Automatic coiler: Automatic coiler is a double-roll irreversible vertical mill. The utility model is characterized in that a pair of high-speed reverse rotating return rolls are arranged behind the work rolls, and the function of which is to deliver the once-wound capillary to the front. Because of the second rolling, the production efficiency is low, and most of the domestic units have been modified or eliminated.  The material of roll is mainly infinite chilled cast iron, nodular cast iron or chilled nodular cast iron with hardness higher than HSD50.


2. Twin-roll continuous rolling mill: continuous rolling mill is a kind of advanced steel tube mill. It places porous capillaries on long mandrel and arranges them on several stand in turn. The roll gap of adjacent stand is 90 degrees. Continuous tube mill rolling. The main materials of continuous roll are infinitely cold-hardened nickel-chromium-molybdenum ductile iron (also known as pearlitic ductile iron), infinitely cold-hardened nickel-molybdenum ductile iron (also known as needle ductile iron), and the hardness of pass is HSD50-65. The first frame of continuous roll designed abroad is made of forged steel or graphite steel to further enhance the strength of the roll.


3. Three-roll continuous rolling mill: The three-roll adjustable limit mandrel mill (PQF) developed by INNSE Company of Italy overcomes the inherent limitation of the twin-roll mill because it will be 360 degrees. This type is divided into three parts. They reduce the linear velocity difference between the bottom and the edge of each roll hole type, so the rolling steel pipe has high precision. The continuous rolls of small PQF mill are integral. The infinite cold hardening ductile iron of nickel-chromium-molybdenum is used. Hardness is controlled at HSD55-65. The continuous rolls for assembling large PQF mills are wear-resistant. Nickel-chromium-molybdenum infinite chilled ductile iron is the best choice. The shaft is made of high strength forged steel, which can be reused after quenching and tempering, thus greatly saving the cost. The structure has been successfully applied in Tianjin Steel Tube Company.


4. Assel mill: Assel mill is a three-roll cross rolling process consisting of three active rolls and one mandrel. The rollers are divided into four parts: the entry cone, the shoulder of the rollers, the flat area and the exit cone. The material is made of 4Cr5MoSiV1 forged steel, cast semi-steel or alloy ductile iron. Heat treatment hardness: forged steel roll is controlled in HSD65-75, semi-steel roll is controlled in HSD50-60, alloy ductile iron roll is controlled in HSD55-65 (this material roll is designed for imported units, and has few successful application examples in China).