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Defects on the inner surface of seamless steel pipes: how to control?

Views: 0     Author: Site Editor     Publish Time: 2021-03-01      Origin: Site

The shortcoming of the internal scab of the hot continuous-rolled seamless steel pipe is that there are dents similar to the size of soybean grains on the inner surface of the seamless steel pipe, and most of the scabs contain dark red or dark gray dirt. The influencing factors of internal scab are: metal oxide removal agent, gasifier processing technology, mandrel lubrication and other factors. Below is a look at how to manipulate the inner surface layer of seamless steel pipe with the seamless steel pipe manufacturer's network editor:


seamless welding factory- GKSTEELPIPE

1. In addition to metal oxides


The metal oxide is required to be in a molten state when the mandrel is pre-pierced. Strict management of its range, etc.


1) The particle size distribution of the powdered metal oxide removal agent is generally specified at 16 meshes.


2) The content of sodium stearate in the metal oxide removal agent should be more than 12%, so that it can be fully ignited in the inner wall of the capillary.


3) According to the total surface area of the capillary, the injection amount of the metal oxide removal agent is determined, which is generally 1.5-2.0g/dm2. The amount of metal oxide removal for capillary gas generators with different diameters and lengths is different.


2. Main parameters of processing technology of gas producer


1) The working pressure of the gas generator should be matched with the diameter and length of the capillary tube to ensure strong purging and sufficient ignition, and no metal oxide removal agent that is not completely ignited can be blown away from the capillary tube by the cyclone.


2) The purge time should be adjusted immediately and according to the length of the capillary, and the norm is that no floating hydroxide in the capillary is blown out.


3) The height-to-width ratio of the nozzle should be adjusted according to the capillary diameter to ensure good alignment. The nozzles must be removed once for each vehicle, and the nozzles must be removed for cleaning after long-term shutdown. In order to ensure that the metal oxide removal agent is evenly purged in the inner cavity of the capillary, optional equipment is used in the process of removing the metal oxide agent in the gas producer, and is equipped with a rotating standard pressure.


3. Mandrel lubrication


The actual effect of mandrel lubrication is not very good or the temperature of the mandrel lubricating fluid is too low, which will cause internal scabs. In order to increase the temperature of the mandrel, the method of cooling the circulating water only once can be used. During the processing, the temperature of the mandrel must be strictly controlled to ensure that the surface temperature of the mandrel is 80-120°C before spraying the lubricating fluid, and the temperature of the mandrel cannot be higher than 120°C for a long time to ensure that the lubricating fluid on the surface is dry and dry High density, operators should always check the mandrel lubrication.


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