Large-diameter seamless steel pipe are those with an outer diameter exceeding 100 mm, wall thickness greater than 0.2, and the outer diameter of a pipe, and large-diameter seamless steel pipes are pierced with steel ingots or solid pipes, and then hot-rolled, cold-rolled, or cold dialed.
At present, China's large-diameter seamless steel tubes mainly produce large-diameter seamless steel tubes. Hot-rolled, thermal-expanded, and hot-expanded seamless steel tubes are 325mm-1220mm in thickness and 120mm in thickness, and can be used to produce non-GB thermal expansion of seamless steel tubes. Expanding seamlessly is what we often refer to as thermal expansion, where the density is relatively low but steel is strongly contracted or ramping methods are used to expand the process of the undersized tube. In a very short period of time, the production of seamless pipes for steel thickening and non-standard special types of time, low cost, high production efficiency, the development trend of today's international rolling field. The
Large-caliber seamless steel tubes are cold-drawn or cold-rolled by cold forming, cold-rolling, and other steel products that are cold-formed and heat-treated without any direct transfer. With the hot rolling (forging) state, high precision cold drawing (rolling) state, good surface quality, low surface roughness, and high mechanical properties, due to the oxide surface of the cold drawn (rolled) steel delivery state is not covered, There is a great deal of pressure, and it is susceptible to corrosion or rust. Therefore, the state of cold drawing (rolling) of steel has strict requirements for packaging and storage. Generally, it needs to be stored in a warehouse, and attention should be paid to a control bank for temperature and humidity.
Large-diameter seamless steels are specially heat-treated after hot rolling or forging. They are not directly delivered after cooling. The state is called hot-rolling or forging, and the hot-rolling (forging) final cooling temperature is generally 800 to 900 degrees. Normally, it is cooled naturally. After being in the air, the hot-rolled (forged) state corresponds to normalizing. The difference is that due to the termination of high and low temperatures in hot rolling (forging), unlike normalizing and strict temperature controlled heating, the microstructure and mechanical properties of steel are better than that of steel. At present, many iron and steel enterprises control rolling, because the temperature control of finishing rolling is very strict. After adopting forced cooling measures, grain refinement of steel and steel conveying have higher mechanical properties. Hot-rolled wire rods are superior to ordinary hot-rolled wire rods. The truth is that there is no twist-controlled cold and hot-rolled (forged) steel delivery state. The surface is covered with a layer of iron oxide, which has certain corrosion resistance, storage and strict requirements as cold. Pulled (rolled) medium-steel steels are delivered in the form of thick steel plates that can be stored in open storage yards or thatched covers. The large-caliber seamless steel tube plant is heat-treated before annealing. This condition is called the state of annealing feed. The main purpose of annealing is to eliminate defects, improve the organization and internal stress left before and after surgery preparation and tissue properties, alloy structural steel, guaranteed hardenability structural steel, cold crucible steel, bearing steel, annealed steel commonly used tool steel , Steam turbine blade steel, heat-resistant stainless steel body cable delivery.
