The domestic seamless steel pipe enterprises are known to reduce the production and maintenance of blast furnaces by 13 steel mills, and it is estimated that the output will be affected by about 1.32 million tons; while the production reduction and maintenance of the rolling line is more concentrated, and it is expected to affect the seamless steel pipe production to reach 2.547 million tons. However, depending on the distribution of its species, it is mainly due to the difference in the degree of loss.
According to analysts, the current maintenance of the steel mills is mainly due to the maintenance of high ore prices, while the price of seamless steel tubes and seamless casing continues to be low, and the finished steel products inventory is also large. However, from the current perspective, blast furnaces have limited overhauls. Steel mills choose the overhauling mills to reduce inventory pressure.
However, if the ore prices continue to maintain high prices in the later period, the blast furnace overhaul will be further expanded. In addition, the downturn in demand is also the main reason for the centralized maintenance of steel plants. It is understood that recently, Sany Heavy Industry and other machinery factories have begun to implement the plan for the exchange of seamless steel tubes for mechanical products due to the high level of funds in machinery inventory, which shows that downstream demand has entered the winter, From July to August, it was the traditional off-season of downstream companies. Demand was so light that steelmakers focused on overhauling during this period. Due to increased production and maintenance, the shortage of seamless steel pipe specifications may increase in the later period of the market, which may cause short-term rebound of seamless steel pipe production process.
1 Hot-rolled seamless steel pipe production process (mainly inspecting process):
Tube blank preparation and inspection △→Pipe blank heating→Punching→Pipe rolling→Reheating of steel pipe→Determining (reducing) diameter→Heat treatment △→Production pipe straightening→Finishing→Inspection △ (Non-destructive, physical and chemical, table inspection) → Storage
2 Cold rolling (pulling) seamless steel pipe main production process:
Billet preparation → pickling lubrication → cold rolling (pulling) → heat treatment → straightening → finishing → inspection
General seamless steel pipe production process can be divided into two kinds of cold drawing and hot rolling. The production process of cold rolled seamless steel pipe is generally more complicated than hot rolling. The pipe blank must be firstly rolled by three rollers, and it must be pressed after extrusion. In the sizing test, if the surface does not respond to cracks, the circular tube must be cut by a mower to cut a blank having a length of about one meter. Then enter the annealing process, annealing with acidic liquids for pickling, pickling should pay attention to the surface whether there is a lot of blistering, if there is a large number of blisters generated that the quality of the steel can not meet the corresponding standard. Appearance of cold-rolled seamless steel pipe is shorter than hot-rolled seamless steel pipe, cold-rolled seamless steel pipe wall thickness is generally smaller than the hot-rolled seamless steel pipe, but the surface looks brighter than thick-walled seamless steel pipe, the surface is not too More rough, caliber does not have too many glitches.
The delivery status of hot-rolled seamless steel tubes is generally after hot-rolled and heat-treated. After the hot rolled seamless steel tubes undergo quality inspection, they must be strictly hand-selected by the staff. After the quality inspection, surface oiling is performed, followed by several times of cold drawing experiments, and after the hot rolling treatment, perforation tests are performed. If the perforation expansion is too large, straightening correction is required. After straightening, it is transported by the transmission device to the flaw detection machine to carry out the flaw detection experiment. Finally, it is labeled and placed in the warehouse after specification.
Round billet → heating → piercing → three-roller oblique rolling, continuous rolling or extrusion → de-spooling → sizing (or reducing) → cooling → straightening → hydrostatic test (or flaw detection) → marking → incoming seamless steel pipe The ingot is made by punching a steel ingot or a solid tube and then hot-rolled, cold-rolled or cold drawn. The specifications of the seamless steel pipe are expressed in millimeters of the thickness of the outer wall.