The cooling method of seamless steel pipe varies with its material. For most steel grades, natural cooling can meet the requirements. For some special-purpose seamless steel pipes, in order to ensure the required organizational state and physical and mechanical properties, there must be a certain cooling method and cooling system. For example, austenitic stainless steel seamless steel pipe needs to be finished rolled at a certain temperature, then quenched with water for solution treatment, and then sent to a cooling bed for natural cooling; GCrIS bearing seamless steel pipe is to make it have a flaky pearlite structure And to prevent the precipitation of reticulated carbides, in order to facilitate the subsequent spheroidizing annealing process, the final rolling should be controlled at above 850 ° C, and then the rapid cooling should be carried out at a speed of 50 to 70 ° C/min. Spray for forced cooling.

The cooling time of the seamless steel pipe is the main basis for determining the length of the cooling bed. The cooling of the seamless steel pipe mainly relies on radiation and convection heat dissipation. The test proves that the temperature of the seamless steel pipe above 500 ℃ mainly relies on the radiation heat dissipation, while the convection conduction heat dissipation is the main method below 500 ℃. In order to reduce the cooling time of seamless steel pipes, reduce the length of the cooling bed and improve the operating conditions of the workshop, forced ventilation on the cooling bed can be considered. The use of forced ventilation below 500 ℃ can shorten the cooling time by 50-40%.

The main defects in the heat treatment of seamless steel pipes are that the iron oxide skin is too thick. The oxidation of the surface of the seamless steel pipe to generate iron oxide scale is a common phenomenon in the thermal process. It is the result of the rolling steam and carbon dioxide in the iron and furnace gas on the surface of the seamless steel pipe.
During heat treatment, if the furnace gas is in a strong oxidizing atmosphere or the heat treatment time is too long, the iron oxide scale on the surface of the entire seamless steel pipe will be thick; if the heating temperature is not uniform, the local iron oxide scale will be too thick. Extend pickling time. The iron oxide scale of the seamless steel pipe is too thick locally and is prone to over-pickling or under-pickling.

In order to prevent the whole or part of the iron oxide scale from being too thick, in the case of open fire heating, positive pressure operation should be used, the heating should be uniform and the heating time should be avoided too long, and the surface of the furnace elbow seamless steel pipe should be dry.