Production process of hot rolled seamless steel pipes

Seamless steel pipes are produced from a solid round steel billet that is perforated to create a hollow tube without any welds on the surface. These pipes, known for their uniformity and strength, are classified into several types based on their production methods, including hot rolled, cold rolled, cold drawn, extruded, and jacked seamless steel pipes. Among these, the hot rolling process is particularly significant, playing a crucial role in determining the quality of the final product.

Hot Rolling Process of Seamless Steel Pipes

The hot rolling process begins by unloading the continuous cast billet into a hot rolling mill, where it undergoes a series of steps to achieve the desired cross-sectional size. The billet is heated and passed through rollers, which hot-roll the material to the required dimensions. After cooling and solidification, the steel is stretched to the specified size using a stretcher, resulting in a finished product that meets the necessary specifications.

Main Production Steps of Hot Rolled Seamless Steel Pipes

The production of hot rolled seamless steel pipes involves several key stages:

Preparation and Inspection of Tube Blank: The raw tube blank is prepared and inspected for quality.

Heating of Tube Blank: The blank is heated to the appropriate temperature for further processing.

Perforation: The heated blank is perforated to create a hollow tube.

Pipe Rolling: The tube is rolled to further refine its dimensions.

Reheating: The steel pipe is reheated as necessary to maintain workability.

Sizing (or Reduction): The pipe undergoes sizing or diameter reduction to achieve the precise dimensions.

Heat Treatment: The pipe is subjected to heat treatment to enhance its mechanical properties.

Straightening: The finished pipe is straightened to ensure uniformity.

Finishing: Additional finishing processes are applied to refine the surface and dimensions.

Inspection: The pipe undergoes rigorous inspections, including non-destructive testing, physical and chemical tests, and individual piece inspection.

Warehousing: After passing all quality checks, the pipes are marked, labeled, and stored in the warehouse.

Quality Control and Delivery

Hot rolled seamless steel pipes are typically delivered in a hot-rolled state after undergoing heat treatment. The production process includes several quality control measures, such as manual inspection, surface oiling, multiple cold drawing tests, and perforation experiments. If the perforation diameter is too large, the pipe is straightened before being transferred to flaw detection equipment for further testing. After all inspections are complete, the pipes are labeled with specifications and stored.

General Production Flow

The overall production flow for seamless steel pipes involves the following steps:

Round Tube Blank Preparation

Heating

Piercing

Three-Roll Cross Rolling, Continuous Rolling, or Extrusion

Removal of Tube

Sizing or Diameter Reduction

Cooling

Straightening

Hydraulic Testing or Flaw Detection

Marking

Warehousing

Seamless steel pipes are typically produced from steel ingots or solid tube blanks that are perforated to create capillary tubes. These tubes are then subjected to hot rolling, cold rolling, or cold drawing to achieve the final product. The specifications of seamless steel pipes are usually indicated by their outer diameter and wall thickness, measured in millimeters.