What is the delivery status?
The delivery state refers to the final plastic deformation or heat treatment state of the seamless tube product. Divided into hot rolling, cold drawing (rolling) state or manufacturing state, and heat treatment state, such as normalizing, quenching and tempering, solid solution, annealing state. The delivery status must be stated in the contract.
What are the delivery states of carbon steel seamless tubes?
1. Carbon steel seamless tubes are cold-drawn, cold-rolled and other cold-formed steel, and the state of direct delivery without any heat treatment is called cold-drawn or cold-rolled state. Compared with the hot-rolled (forged) state, the steel in the cold-drawn (rolled) state has high dimensional accuracy, good surface quality, low surface roughness, and high mechanical properties. The surface is not covered by scale, and there is a large internal stress, which is very easy to be corroded or rusted. Therefore, the packaging, storage and transportation of cold-drawn (rolled) steel products have strict requirements, and generally need to be kept in the warehouse. And should pay attention to the temperature and humidity control in the warehouse.
- Carbon steel seamless tubes are no longer subject to special heat treatment after hot rolling or forging, and are delivered directly after cooling, which is called hot rolling or hot forging state. The termination temperature of hot rolling (forging) is generally 800°C ~ 900°C After that, it is generally cooled naturally in the air, so the hot rolling (forging) state is equivalent to normalizing treatment.
The difference is that the termination temperature of hot rolling (forging) varies from high to low, unlike the strict control of normalizing heating temperature, so the fluctuation of steel structure and performance is larger than that of normalizing. Many iron and steel enterprises adopt controlled rolling. Due to the strict temperature control of the final rolling and the forced cooling measures after the final rolling, the grains of the steel are refined, and the delivered steel has high comprehensive mechanical properties. This is the reason why the performance of non-twist-controlled cold and hot-rolled wire rods is superior to that of ordinary hot-rolled wire rods. The steel delivered in the hot-rolled (forged) state has a certain corrosion resistance because the surface is covered with a layer of iron oxide scale. Storage, transportation and storage The requirements are not as strict as those delivered in the cold-drawn (rolled) state. Large and medium-sized steel and medium-thick steel plates can be stored in the open yard or after being covered with thatch.
- Carbon steel seamless tubes are annealed and heat-treated before leaving the factory. This delivery state is called the annealed state. The purpose of annealing is mainly to eliminate and improve the structural defects and internal stress left over from the previous process, and to prepare for the structure and performance of the subsequent process. Alloy structural steel, structural steel with guaranteed hardenability, cold heading steel, bearings Steel, tool steel, steel for steam turbine blades, and cable-shaped stainless heat-resistant steel are usually delivered in the annealed state.
- Carbon steel seamless steel pipes are heat-treated by normalizing before leaving the factory. This delivery state is called normalizing state. Since the positive heating temperature (Ac3+ 30~50°C for hypoeutectoid steel and Accm+ 30~50°C for hypereutectoid steel) is strictly controlled than the hot rolling termination temperature, the microstructure and properties of seamless steel pipes are uniform. Compared with the steel in the annealed state, since the autumn heating temperature is strictly controlled than the hot rolling termination temperature, the structure and properties of the seamless steel pipe are uniform. Compared with the seamless steel pipe in the annealed state, Yu Zhengqiu has a faster cooling rate, the number of pearlite in the structure of the seamless steel pipe increases, and the grains of the pearlite layer and steel are refined, so it has higher comprehensive mechanical properties, and It is beneficial to improve the Widmanstatten structure of low carbon steel and the cementite network of hypereutectoid steel, and can prepare the structure for further heat treatment of finished products. Seamless steel pipes are often delivered in the normalizing state.
- High-temperature tempering state. Carbon steel seamless steel pipes are treated with high-temperature tempering before leaving the factory. This delivery state is called high-temperature tempering state. The high-temperature tempering temperature is high, which is conducive to completely eliminating internal stress and improving the plasticity and toughness. Carbon structural steel pipes, alloy steel pipes, and structural steels with guaranteed hardenability can be delivered in a high-temperature tempered state. Some martensitic high-strength stainless steel seamless pipes, due to their high hardenability and the strengthening effect of alloying elements, are often subjected to a high-temperature tempering after quenching (or tempering) to properly aggregate carbides in the steel. , a tempered sorbite structure with relatively coarse carbide particles (similar to the spheroidizing annealed structure) is obtained. Therefore, the steel in this delivery state has good machinability.
- The steel has been solution treated before leaving the factory, and this delivery state is called the solution treatment state. This state is mainly suitable for the treatment of austenitic stainless steel before leaving the factory. Through solution treatment, a single-phase austenite structure is obtained to improve the toughness and plasticity of the steel, to create conditions for further cold working (cold rolling or cold drawing), and to prepare for further precipitation hardening.
As a manufacturer of stainless steel tube and carbon steel tubes, Husteel Industry Group. specializes in the production and supply of seamless steel tubes: including thin-wall/thick-wall seamless tubes, precision seamless tubes, small-diameter/large-diameter seamless tubes, and various specifications and materials , large inventory, rich experience, can provide customized services according to customer requirements.
