Learn more about Praxair’s Argon Oxygen Decarburization process that is used to make over 75% of the world’s stainless steel. Argon Oxygen Decarburization (AOD) Treatment is the recognized standard for stainless steel refining worldwide. Whether you are producing castings, wrought . Argon Oxygen Decarburization, frequently referred to as “AOD”, is an advanced technology for the refinement of iron, nickel, and cobalt based alloys. By.
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To achieve this, alloy additions are made with defarburization that have a higher affinity for oxygen than chromium, using either a silicon alloy or aluminum. Decarburization occurs when dissolved carbon reduces the chromium and iron oxides that form.
If necessary, additional raw materials may be charged for small chemistry adjustments before tapping. In case of those steel grades which can tolerate nitrogen, a mixture dwcarburization oxygen and nitrogen can also be blown. The effectiveness of reduction step is dependent on many factors including slag basicity and composition, temperature, mixing conditions in the converter and solid addition dissolution kinetics.
Oxidation of carbon continues, but oxidation of chromium is limited.
After the change from nitrogen to argon, nitrogen is removed from the bath both by evolved carbon monoxide and argon. This argon dilution of oxygen minimizes unwanted oxidation of precious elements contained in specialty steels, such as chromium. As molten stainless steels do not generate foam, and most stainless steel refining processes are side or bottom-blown, the dimensions of a stainless refining converter are smaller than a comparable BOF basic oxygen furnace converter.
Other trimming alloy additions might be added at the end of the step. Electro-slag remelting Vacuum arc remelting Argon oxygen decarburization. Argon-oxtgen designs exist for normalizing the flow in the annular gap.
For converters that tap into a ladle held by a crane, a sliced cone top section is often used. The formation of high basic slag and the reduction of oxygen potential in the liquid steel bath are good conditions for sulphur removal. The liquid metal is argon-ozygen from transfer ladle to AOD converter.
Desulphurization to very low levels is generally easier in dolomitic refractories because very basic slags can be used without detrimental effects on the bricks. The bath is then stirred with inert gas, typically for around five to eight minutes. After sulfur levels have been achieved the slag is removed from the AOD vessel and the metal bath is ready for tapping. Careful manipulation of slag, as it precipitates in the reaction, is important.
Bessemer process Open hearth furnace Electric arc furnace Basic oxygen process. The process is so popular because it combines higher metallic yields with lower material costs. At this point, the process gases can be shut off and a small cooling flow protects the tuyeres. After the transfer of liquid steel containing iron, chromium, carbon and nickel from EAF or IF to the AOD converter, high carbon ferro chrome is added and the blow is started with the blowing of inert gas argon, nitrogen and oxygen mixture.
The system will be tailored to match your current operation with added features found only on the new systems. After tapping, the ladle is often stirred for composition homogenization and temperature uniformity along with flotation of inclusions.
The installation of a lance and introduction of oxygen in the early stages of decarburization can reduce the time for a heat. To drive decarbburization reaction decarburizatoon the forming of CO, the partial pressure of CO is lowered using argon or nitrogen.
The molten metal is then decarburized and refined in an AOD converter to less than 0. This argon dilution minimizes unwanted oxidation of precious elements contained in specialty steels, such as chromium. Desulphurization is achieved by having a high lime concentration in the slag and a low oxygen activity in the metal bath. Praxair can review your system and design an upgrade using:.
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The molten metal is then decarburized and refined in a special AOD vessel to less than 0. A arhon-oxygen modification of the AOD process involves the use of top blowing lance in addition to the side blowing tuyeres. AOD process decagburization has three major steps. Typical internal volumes of AOD converters are in the range 0. These additions usually consist of desired amounts of high carbon ferrochromium, stainless steel scrap, carbon steel scrap, nickel, iron, high carbon ferromanganese, and molybdenum oxide.
Other trimming alloy additions might be added at the end of the step. The desire to increase the productivity has led to continuous charging of raw materials during the blow period as well as reduction period. Since the blowing is done along with argon it is possible to carry out the decarburization at a lower temperature. Annealing Low hydrogen Short circuit. Other benefits include pinpoint accuracy in chemistry control down to 0.