RU2699887C1 - Method of producing high-precision alloy 42hnm (ep630y) on nickel basis - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: invention relates to special metallurgy, specifically to methods of producing 42HNM alloy on nickel base with recycling of wastes. Method consists of preparation of charge materials containing standard and off-standard wastes, including chips, formation of filling of vacuum furnace, subsequent vacuum remelting and metal casting, at that, remelting is carried out at high vacuum with electromagnetic mixing, and metal casting is performed in vacuum in steel pipes or molds with obtaining secondary activated standardized waste in form of electrode, which in the composition of charge materials fall into open induction furnace with protective cover for alloying 42HNM alloy.EFFECT: method provides resource saving due to waste recycling, including saving of expensive and scarce charge materials, and ensures compliance with chemical composition requirements.6 cl, 1 dwg, 2 tbl

Description

1. The technical field

The invention relates to the field of special metallurgy, specifically to methods for producing a precision alloy 42XHM (EP630U) on a nickel basis, intended for products for special purposes; especially thin-walled pipes used for the manufacture of parts in reactor engineering, cladding of fuel elements, SVP and RIN (working sources of neutrons), elements of the active zone of nuclear reactors, using waste recycling, and can also be used to produce other alloys.

2. The prior art

The well-known "Method for producing casting heat-resistant nickel-based alloys using waste" (Patent RU No. 2190680 (С22С 1/02) 2001), by refining waste in vacuum. The disadvantage of the technical solution is a narrow range of technological modes for local compositions that does not take into account the heterogeneity of the waste and the possibility of adjusting the composition.

The well-known "Method for the production of carbon-free casting heat-resistant nickel-based alloys" (Patent RU No. 2310004 (С22С 1/03, С22С 19/05, С22С 1/06) 2005), in which charge materials melted in vacuum are refined in two stages by introduction into the oxidizer melt in an inert gas atmosphere and the subsequent introduction of chromium, active alloying elements, rare-earth metals and calcium refining in a vacuum. The disadvantage of the technical solution is that it does not allow smelting alloys with a high chromium content due to high fumes and oxidation, as well as the inability to obtain low levels of harmful impurities in the alloy.

The well-known "Method for producing heat-resistant nickel alloys by processing metal waste" (Patent RU2398905 (C22C 19/03, C22B 7/00) 2009), including the loading of metal waste, its melting and subsequent refining. The disadvantage of this method is the inability to adjust the composition in preparation for the main smelting.

Also known, adopted by the applicant for the closest analogue, “Method for producing casting heat-resistant nickel-based alloys” (Patent RU No. 2470081, (С22С 1/02, С22В 9/02), 2011).

The method includes the preparation of charge materials in the preparation of nickel-based alloys, including cleaning of technical mechanical impurities of substandard waste, introducing a composition of purified substandard waste identical to the alloy into the composition of charge materials, and their subsequent re-melting in vacuum.

The disadvantage of this method is the lack of effective operations of chemical-physical adjustment of substandard waste at the stage of preparation of the charge materials.

3. The invention

3.1. Statement of the technical problem

Resource-saving, including saving expensive and scarce charge materials during smelting of the precision alloy 42KHNM (EP630U) on a nickel basis using waste recycling by activating their unrealized reserves.

The result of solving a technical problem

The resource-saving task was solved by involving in the production of the precision alloy 42KHNM (EP630U) secondary conditioned waste obtained by the preparation and refining of our own brand of conditioned and substandard waste. At the same time, in secondary conditioned waste, the identical chemical composition of the main charge charge is obtained.

3.2. Features

In contrast to the known technical solution for the production of nickel-based alloys, it includes the preparation of charge materials, purification of technical mechanical impurities of substandard waste, the introduction of a composition of purified substandard waste identical to the grade alloy into the composition of charge materials, and their subsequent re-melting in vacuum; in the claimed technical solution at the stage of preparation of charge materials from conditioned and substandard waste, for their recycling and receipt of secondary activated conditioned waste, they are sequentially smelted in a vacuum induction furnace under high vacuum (not higher than 25 × 10 ^-3 mm Hg) s using electromagnetic stirring (EMF), after which casting is performed through a pouring trough with two baffles and a foam-ceramic filter installed, which ensures physico-chemical cleaning and a product with an identical chemical composition of the main charge load, which is introduced into the composition of the charge of open induction smelting of grade metal in an amount of up to 40%.

The filling of the vacuum induction furnace is formed using standard and non-standard waste of its own brand, including shavings in an amount of up to 40% of the weight of the filling. In this case, the chips are preliminarily calcined in an annealing furnace in a cast-iron brazier with a bulk layer of not more than (600–800) mm at a temperature of (500–800) ° C for 2–3 hours. Chip cooling is carried out with the furnace for 7 ÷ 8 hours to a temperature of 20 ÷ 50 ° C.

The alloy mixture 42XHM (EP630U) is smelted in a vacuum induction furnace under high vacuum (not higher than 25 × 10 ^-3 mm Hg). After the filling is melted at the melt temperature (1480 ÷ 1520) ° С, the metal is kept under vacuum for 10-15 minutes with the electromagnetic stirring connected for 5-7 minutes in the middle of the exposure.

Metal is cast in a vacuum at a temperature of (1540 ÷ 1560) ° C in steel pipes ∅80 ÷ 100 mm or in molds ∅200 ÷ 250 mm with heat-insulating inserts through a casting trough with two baffles installed in it, for cutting off slag, and specially prepared ceramic foam filter.

In addition, the lateral surface of the melted billets, before further use for smelting of branded metal, is subjected to continuous abrasive cleaning of the surface to a depth of 5-7% of the diameter of the billet and the technological trim on both sides is removed.

3.3. List of drawings

In FIG. 1 is a structural block diagram of a method for producing a precision alloy 42KHNM (EP630U) on a nickel basis, where 1. - Formation of filling an open induction furnace; 1a. - “Fresh” (standard) charge components; 1b. - Corrective components of the mixture (alloying additives); 2. - Open induction (OI) smelting of grade metal; 3. - Casting electrodes OI smelting; 4. - Processing of electrodes OI smelting; 5. - Production of metal products; 6. - Substandard waste (6-1. - Underfilling, scrap; 6-2. - Profitable parts; 6-3. - Chips); 7 - Conditioned technological waste (7-1. -Technological trimmings; 7-2. - Residues from cutting); 8. - The formation of filling the vacuum induction (VI) furnace; 9. - Mechanical cleaning and waste treatment; 10.

- Smelting in a vacuum induction (VI) furnace; 10a. - "High" vacuum and electromagnetic stirring; 11. - Casting of electrodes through a slag cut-off system and metal filtration; 12. - Processing of electrodes of VI smelting; 13. - Secondary activated conditioned waste.

SI smelting - open induction smelting in FIG. 1 block 2; VI smelting

- vacuum induction smelting in FIG. 1 block 10.

4. Description of the invention

In the claimed technical solution, at the stage of preparation of the charge materials, operations of chemical-physical adjustment of the waste of its own brand are carried out, while the following steps are sequentially performed to obtain a precision nickel-based alloy (Fig. 1.):

- preliminary smelting in a vacuum induction furnace of own brand waste, including shavings in an amount up to 40% of the filling weight, at high vacuum (not higher than 25 × 10 ^-3 mm Hg) (Fig. 1, block 8, 10 );

- after filling the melt at the melt temperature (1480 ÷ 1520) ° С, the metal is kept under vacuum for 10-15 minutes with the electromagnetic stirring connected for 5-7 minutes in the middle of exposure using electromagnetic stirring (Fig. 1, block 10 and 10a) ;

- casting of metal in vacuum through a casting chute with two baffles installed, for slag cut-off, and a specially prepared foam ceramic filter at a temperature of (1540 ÷ 1560) ° С in steel pipes ∅80 ÷ 100 mm or in molds ∅200 ÷ 250 mm with heat-insulating inserts (Fig. 1, block 11) designed to obtain a shortened profitable part of the ingots, electrodes, cast bar stock, which excludes the penetration of the shrink shell into the body of the ingot and prevents the formation of transverse cracks;

- smelting of grade metal in an open induction furnace with a protective cover using the resulting secondary activated conditioned waste (Fig. 1, block 1 and 2), while:

- filling the vacuum induction furnace is formed using chips (up to 40% of the weight of the filling) and lump waste of its own brand (Fig. 1, block 8);

- the chips are preliminarily calcined in an annealing furnace in a cast-iron brazier with a bulk layer of not more than (600–800) mm at a temperature of (500–800) ° C for 2–3 hours;

- the chips are cooled with the furnace for 7 ÷ 8 hours to a temperature of 20 ÷ 50 ° C;

- smelting in a vacuum induction furnace is carried out at high vacuum (not higher than 25 × 10 ^-3 mm RT.article) with the connection of electromagnetic stirring for 5 ÷ 7 minutes in the middle of exposure to metal under vacuum for 10 ÷ 15 minutes after the filling is melted at a temperature melt (1480 ÷ 1520) ° C (Fig. 1, block 10 and 10a);

- metal is cast in a vacuum at a temperature of (1540 ÷ 1560) ° C in steel pipes ∅80 ÷ 100 mm or in molds ∅200 ÷ 250 mm with heat-insulating inserts through a casting trough with two baffles installed in it, to cut off the slag, and specially prepared ceramic foam filter (Fig. 1, block 11);

- the side surface of the melted charge preforms is subjected to continuous abrasive cleaning to a depth of 5–7% of the electrode diameter before being used for smelting grade metal and the technological trim on both sides is removed (Fig. 1, block 12);

- prepared charge billets are used for smelting grade metal in an amount up to 40% of the weight of the heat (Fig. 1, block 13).

The developed progressive technology for the smelting of billets of alloy 42KHNM (EP630U) includes:

- return to production of scarce and expensive materials (waste recycling - gates, scrap, treads from the crucible, profitable parts of open ingots, shavings, technological trimmings, residues from cutting) (Fig. 1, block 6 and 7);

- full use of all types of waste without compromising the properties of the alloy and ensuring a narrowed chemical composition, as well as ensuring a low nitrogen content in the grade metal within the recommended ranges (0.03-0.15%) (Fig. 1, block 10 and 10a);

- quick establishment of a liquid bath in the initial period of the OI smelting, reducing the time of melting of the metal and ensuring the addition of metallic chromium directly into the liquid metal.

Using the proposed method allows for the cleaning of technical (calcining chips, abrasive cleaning) and physico-chemical impurities (the ability to adjust the chemical composition) of materials.

Using the proposed method allows to obtain charge blanks clean with respect to non-metallic and slag inclusions, and also saves expensive and scarce charge materials (nickel, chromium, molybdenum, tungsten) when smelting grade metal.

5. An example of a specific implementation (implementation of the method)

The method can be implemented on the integrated installation of standard equipment:

but. chip annealing is carried out in a single-chamber gas hearth furnace;

b. smelting of billets (secondary activated conditioned waste) is carried out in a 1.5-ton vacuum induction furnace equipped with a system for slag cut-off and metal filtration;

at. continuous abrasive cleaning of charge billets is carried out on a peeling-grinding machine;

d. the removal of technological trim on both sides of the workpieces is carried out on an abrasive cutting machine;

d. smelting of grade metal using secondary activated waste is carried out in an open induction furnace with a capacity of 1.0 t with a protective cover.

The filling for smelting activated conditioned waste includes 60% of our own conditioned (technological) waste and 40% of shavings (return of our own production), previously cleaned as follows:

- calcination in an annealing single-chamber gas furnace with a roll-out hearth in a cast-iron brazier with a bulk layer of not more than (600 ÷ 800) mm at a temperature of (500 ÷ 800) ° C for 2 ÷ 3 hours;

- then it was cooled with the furnace for 7 ÷ 8 hours to a temperature of 20 ÷ 50 ° C.

Then, smelting was performed in a 1.5-ton vacuum induction furnace under high vacuum (not higher than 25 × 10 ^-3 mm Hg). After the filling was melted at the melt temperature (1480 ÷ 1520) ° С, the metal was kept under vacuum for (10 ÷ 15) minutes and the electromagnetic stirring was connected for 5-7 minutes in the middle of the exposure.

The metal was cast in vacuum at a temperature of (1540 ÷ 1560) ° С in steel pipes ∅80 ÷ 100 mm and in molds ∅200 ÷ 250 mm with heat-insulating inserts through a casting trough with two baffles installed in it, for cutting off the slag, and specially prepared ceramic foam filter. Table 1 shows the chemical composition of the smelted charge stock (activated conditioned waste).

Next, the lateral surface of the melted charge preforms was subjected to continuous abrasive cleaning on a rough grinding machine to a depth of 5-7% of the electrode diameter before being used for smelting grade metal and the technological cut was removed from both sides on a cutting machine.

Prepared billets were used for smelting in an open induction furnace of branded metal alloy 42XHM (EP630U) as activated (secondary conditioned) waste in an amount of up to 40% of the weight of the heat. This made it possible to start a liquid bath in the initial melting period, to reduce the time of metal melting, to ensure the addition of metallic chromium directly to liquid metal, and, as a result, to reduce the consumption of “fresh” charge components by up to 40%.

Table 2 shows the results of acceptance tests of a ∅60 mm pipe billet of alloy 42KHNM (EP630U) smelted using activated conditioned waste.

Table 2 shows that the properties of the metal smelted using activated waste meet the requirements and have a margin of all characteristics.

The claimed technical solution was tested in a production environment at JSC Metallurgical Plant Elektrostal with a positive result.

This technology allows to save expensive and scarce charge materials (nickel, chromium, molybdenum, tungsten), and reduce the cost of production of 42KHNM alloy electrodes (EP630U) for further redistribution by 10%.

Claims (6)

1. A method of producing a nickel-based alloy 42XHM by disposing of conditioned and substandard waste, including the preparation of charge materials containing conditioned and substandard waste, including shavings, forming a vacuum furnace filling, subsequent vacuum induction remelting and metal casting, characterized in that the vacuum induction remelting carried out under high vacuum with electromagnetic stirring, and the metal is cast in vacuum at a temperature of 1540 ÷ 1560 ° C in steel pipes ∅80 ÷ 100mm or ∅200 ÷ 250mm with receiving secondary activated conditioned waste in the form of an electrode, which, as part of the charge materials, is fed into an open induction furnace with a protective cover for smelting 42XHM alloy. 2. The method according to p. 1, characterized in that before the formation of the filling, the chips are preliminarily calcined in an annealing furnace in a cast-iron roaster with a bulk layer of not more than 600 ÷ 800 mm at a temperature of 500 ÷ 800 ° C for 2 ÷ 3 hours, then it is cooled with the furnace for 7 ÷ 8 hours to a temperature of 20 ÷ 50 ° C. 3. The method according to p. 1, characterized in that the vacuum induction remelting is carried out at high vacuum not higher than 25 × 10 ^-3 mm Hg, after melting the filling, the metal is kept under vacuum for 10-15 minutes at a melt temperature of 1480 ÷ 1520 ° C, while in the middle of the exposure carry out electromagnetic stirring for 5 ÷ 7 minutes. 4. The method according to p. 1, characterized in that the casting of metal into steel pipes or molds is carried out through a casting chute with two baffle plates installed in it for cutting off slag and a ceramic foam filter. 5. The method according to p. 1, characterized in that the lateral surface of the molten electrodes from the secondary activated conditioned waste is subjected to continuous abrasive cleaning to a depth of 5-7% of the diameter of the electrode and removal of the technological edge on both sides before being fed to the induction furnace for smelting 42XHM alloy . 6. The method according to p. 1, characterized in that the electrodes from the secondary activated conditioned waste are fed into the induction furnace in an amount up to 40% by weight of the heat.

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