It analyzes the role of the main elements in the austenitic stainless steel, the tissue of steel, the mechanical performance, the resistance of corrosion resistance and the high temperature performance, and the low temperature performance, and explain the principles of reasonable selection in the design of petrochemical devices.

Rice carburizing extremely uneven

The problem of ethylene furnace tubes and some other equipment is not easy to be perceived by people. It is unpredictable and uneven. The mathematical model developed according to operating experience is a little helpful for the total carburizing rate. Unfortunately, none of the existing models are absolutely accurate or satisfactory. The main reason is that the carburizing is uneven. Temperature itself is not a decisive factor.

Many years ago, people thought that the surface conditions of the tube were an important factor, but it was no longer the only factor that played, because these tubes were the same when they started to use, as well as the conditions for many years. This unevenness also brings a problem, that is, the degree of carburizing cannot be determined. Crystal carburizing makes normal non -magnetic forging (rolled) and casting heat -resistant alloys into magnetic. For many years, this magnetic permeability is used to calculate the degree of carburizing. The measured device used from handheld magnets to currently technically advanced multi -frequency vortex. Although the vortex can not only help to determine the carburizing rate, but also determine the carburizing form, due to the changes in the previous discussion, more attention must be paid to the conclusion. There are other benefits to conduct such a survey in the radiation heat area. The carburizing figure can show an uneven combustion form, otherwise it may not be found. They also help different metallurgical treatment of furnace management alloys. For example, for multi-pipe pipes and vapor inlet pipes, low-cost, low-nickel-improved HP alloys can be used, and 35CR-45NI alloys are used for high-cost but more durable.

Metal powder

Metal powder is considered a common form of carburizing in the process of refining and petrochemical production. Although they have some similarities, it is different from traditional carburizing in many aspects. It consumes metal at a very fast speed, while normal carburizing does not consume metals; the depth of carburizing before metal loss is usually shallow, but it is very strong. It is often related to the carbon dioxide CO/CO2/H2 airflow. These airflows are often related to reorganization, synthetic gases, partial oxygen or other production processes. Metal powder usually occurs within the temperature range of 900 ~ 1600 (482 ~ 871 ° C), and the highest response speed is the highest when 1300 ~ 1350 (704 ~ 832 ° C). This reaction speed can be very fast, and the consequences are unimaginable. Its losses are the surface of the surface. Metal powder can not predict at all, and most of the stainless steel and heat -resistant alloy will be eroded. It is effective to use gas diffusion heat -plating, and it can also be controlled when steam, sulfur or ammonia is added. However, the most active solution is to reduce CO division and adjust the gas composition.

Nitriding

Nitrogen exudation is similar to carburizing. When chromium and other elements are combined with nitrogen to generate crispy nitride, nitrogen seepage occurs. When carbon steel, low -carbon steel, low alloy steel and stainless steel are at a high temperature nitrogen -containing environment, nitrogen seepage is usually occurred. Like the condition of carburizing, because the solubility of nitrogen in nickel is low, the ability of high nickel alloy is strong. 72%alloy 600 nickel is often used in thermal treatment industry, and accidentally used in refining and petrochemical industries with a temperature of 650 (343 ° C), which contains ammonia. Compared with the alloy 800h and the casting improvement HP, due to low economic and intensity factors, the application of alloy 600 in the refining and petrochemical industry is very small. These alloys are not not eroded, but their cost -effectiveness is better. Although nitrogen molecules are very stable, the fully disintegration effect at the combustion temperature makes the 800h or HP furnace tube occur at 1850 (1010 ° C) or higher metal temperature.