Comprehensive protection of the metal jet from oxidation
23.05.2017
Joint work with the technical and scientific staff of metallurgical plants allowed the company PROMATEKHNOLOGII to achieve significant results in the direction of reducing marriage during metal pouring. This technology solves one of the problems. of modern metallurgical production – protection of the metal jet from oxidation during pouring.
One of the options for solving the problem was a device to protect the metal jet from oxidation when pouring a car. St. USSR for the invention No. 1502173, publ. 1989.08.23, IPC4 B22D7/12. The main disadvantage of this protection device is the danger of burning the refractory pipe, which is made in the form of corrugated shells-screens with heat resistance; gas-tight fabric. This leads to a decrease in the reliability of the protection of the metal jet from the secondary. oxidation during its passage through this device.
This device metal jet protection device eliminates the danger of burning the refractory pipe from metal splashes while maintaining the flexibility of this refractory pipe, which allows to increase the reliability of protecting the metal jet from its secondary oxidation, thereby improving the quality of the metal and reduce marriage.
Proposed metal jet protection device includes an outlet cup for supplying a jet of molten metal, which is installed with an annular gap to the internal section of the refractory pipe and located on top a channel for receiving molten metal, a gas distribution unit for supplying inert gas to the indicated annular gap. The refractory pipe is made flexible from a special heat-resistant elastic material, while inside. inside the refractory pipe there is a frame sleeve that burns, and outside the refractory pipe there is a bandage wire.
The cross-section of the refractory pipe is made in the form of an ellipse to ensure the transverse movement of the outlet glass for supplying a jet of molten metal. The internal cross-section of the refractory tube is 3 to 4 diameters of the molten metal jet, and the external cross-section of the refractory tube is 1.0 to 1.15 of the external cross-section of the channel for supplying the molten metal to the mold. Refractoriness of refractory pipe, is 1100-1600 0С, and the density of its material is from 150 to 250 kg/m3.
The execution of the refractory pipe from a special refractory elastic material allows to exclude the possibility of burning this refractory pipe from splashes of metal, as due to the absence of a corrugated surface inside this pipe, and due to the higher fire resistance of the material itself, which has a fibrous structure, and the pipe itself has a flexible and thick-walled form. At the same time, the location inside the a refractory pipe that burns in the first seconds of pouring metal, a frame sleeve, and an externally refractory pipe with a bandage wire arrangement, allows you to ensure both the required shape of this pipe and its necessary flexibility when centering a multi-ton bucket with metal over it. And all this leads to an increase in the reliability of the protection of the metal jet against its secondary oxidation when passing through this device.
Making the frame sleeve from cardboard allows you to ensure that it burns out in the first seconds of metal pouring.
The execution of the cross-section of the refractory pipe in the form of an ellipse allows for the possibility of lateral movement of the outlet cup for supplying a jet of molten metal when a multi-ton ladle with metal is centered over this pipe.
This set of essential features allows, compared to the prototype of the device to protect the metal jet from oxidation during pouring, to provide an exception. the possibility of burning a refractory pipe from splashes of metal, while maintaining the flexibility of this refractory pipe. And this makes it possible to increase the reliability of the protection of the metal jet against its secondary oxidation. In addition, the simplification and reliability of fixing the gas distribution unit above the refractory pipe is ensured.
The test of such a device for protecting the metal jet from oxidation during pouring showed that during the pouring of metal, oxides build up on the edge of the outlet glass. are not formed, which creates prerequisites for excluding the impact of oxidized portions of metal inside the casting system and into ingots (products). This prevents the formation of products of the interaction of metal components with oxidized portions of the metal. In addition, environmental protection is ensured when pouring metal due to the complete exclusion of its splashing, as well as a reduction of thermal radiation at the same time.
This device was successfully tested at OJSC "Interpipe NTZ". At the same time, the tests showed a significant economic effect. in the form of a marriage reduction from 30 to 70 percent, depending on the steel grades and technical requirements applied to the products.
Effectiveness of using this device increases when pouring steels with a high content of alloying elements, such as aluminum, titanium, vanadium.
This effect occurs due to the action of excess pressure of argon. At the same time, the metal stream not only does not come into contact with air during the pouring process, but is also enriched with argon, which in turn is released from the ingot during the filling and crystallization of the metal. At the same time, non-metallic inclusions are removed, as well as hydrogen and oxygen, which partially coincides with the vacuuming of steel, and leads to an increase in its quality.
A number of factors can be attributed to the advantages of the metal jet protection device against oxidation during pouring: