RU2807260C1 - METHOD FOR MANUFACTURING BRONZE RODS “БрХ08” - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method for the production of rods from low-alloy heat-resistant copper-based alloys obtained by electroslag refining of consumable electrodes of vacuum induction smelting, suitable for the manufacture of products used at elevated temperatures. The method for manufacturing rods from “БрХ08” bronze includes smelting “БрХ08” bronze ingots, hot rolling of billets obtained from the ingots and their further cold deformation. Ingots are smelted in a vacuum induction furnace, followed by forging to produce consumable electrodes, and their electroslag refining to produce ingots, which are pressed in one step with a total degree of deformation of 90%. After hot rolling, the hot-rolled billets are pickled, and cold deformation is carried out by drawing to produce rods.

EFFECT: ensuring high level of mechanical properties.

3 cl, 6 dwg, 4 tbl, 1 ex

Description

1. Technical field

The invention relates to the field of non-ferrous metallurgy, in particular, to a method for the production of rods from BrKh08 bronze, obtained by electroslag remelting of consumable electrodes of vacuum induction smelting, suitable for the manufacture of products used at elevated temperatures.

2. Prior art

There is a known “Method for the manufacture of contact wires” (patent RU 2236918, class B21B 1/46, published on September 27, 2004), which includes obtaining a melt, alloying it, drawing a cast billet and forming the required wire profile from it by plastic deformation. In this case, the melt is produced in a furnace with an inert atmosphere, the working space of which consists of three zones - a melting zone, an alloying zone and a zone for dispensing the resulting melt into crystallizers for drawing the cast billet from them. Elements having hexagonal or tetragonal crystal lattices are used as alloying elements. The formation of the wire profile is carried out in two stages - first, a rod is obtained by drawing with a degree of deformation of 15-50%, from which the required wire profile is then obtained by rolling with a degree of deformation of 50-70%.

The disadvantage of this technology is limited productivity, because There is a step-by-step local crystallization of the melt, which requires large energy costs to maintain a fairly large volume of the melt in the liquid phase for a long time. In terms of mechanical properties, wires made of copper and strain-hardening low-alloy copper alloys demonstrate a tensile strength of no higher than 390 MPa and a relative elongation of 3-5%.

The “Method of manufacturing electrical contact wires for high-speed railway transport” is known (patent RU 2685842, class B21C 23/08, C22F 1/08, published 04/23/2019). The method includes feeding the alloy into a mold, crystallizing the alloy in the form of a continuously cast billet, deforming the said billet into a wire rod, hardening, aging at 400-500°C, and forming an electrical contact wire. Hardening is carried out immediately after crystallization from a temperature of 900-1000°C, deformation onto the wire rod is carried out by radial compression with a total accumulated degree of deformation of at least e=1.5, and the formation of an electrical contact wire with a shaped profile is carried out by sequentially combining in one operation equal-channel angular pressing according to “Conform” scheme and pressing at a temperature not exceeding 500°C, with aging carried out as a finishing operation.

The disadvantage of this method is the production of wires that have insufficiently high resistance to contact wear due to the emerging grain-subgrain structural state in the volume of the workpieces, which has a high anisotropy of mechanical properties compared to the grain type of structure. Another disadvantage is the limited productivity of the method associated with the technical capabilities of serial forging machines.

The “Method of rolling round profiles” is known (patent RU 2237529, class B21B 1/02, published 10.10.2004). The method involves compressing the strip in pre-finishing oval and finishing round gauges. In pre-finishing and finishing gauges, the strip is crimped with draw ratios of 1.18-1.30 and 1.20-1.35, respectively. Compression in the finishing gauge is carried out with a support of 100-250 N with a ratio of the width of the finishing gauge to its height equal to 1.009-1.018.

The disadvantage of the known method is that when rolling a strip in continuous roughing and finishing groups of stands of a section rolling mill, due to a mismatch in the speeds of the strip entering the finishing group of stands and exiting the roughing group, either the strip tightens or gets stuck in an emergency - “drilling”. This reduces the quality of varietal profiles and the yield.

The “Method of thermomechanical processing of promising copper alloys” is known (patent RU 2778130, class C22F 1/08, published 08/15/2022). The method includes rolling, equal-channel angular pressing and drawing, while hot rolling is carried out at a temperature of 700°C to a degree of deformation of 0.5-2, continuous equal-channel angular pressing is carried out to a true degree of deformation of 1-2 at a temperature corresponding to the development of continuous dynamic recrystallization with strain aging, the drawing operation is carried out to a true degree of deformation of 1-2 at a temperature corresponding to the development of continuous dynamic recrystallization with strain aging.

The disadvantage of this method is the heterogeneous microstructure of the final material, as well as complex and expensive technological equipment.

Also known, accepted by the applicant as the closest analogue, is “Method of thermal deformation processing of chrome bronze rods” (patent RU 2327807, class C22F 1/08, published on June 27, 2008), including smelting an ingot, hot rolling of an ingot to obtain a hot-rolled billet and cold rolling.

The disadvantages of the prototype include the lack of effective operations that provide sufficient margin and stability of mechanical properties.

1. Essence of the invention

1.1. Statement of technical problem

The technical objective of the claimed invention is to increase the mechanical properties of rods made of BrKh08 bronze.

The result of solving a technical problem

The solution to the set technical problem is achieved by first smelting a BrKh08 bronze ingot in a vacuum induction furnace, followed by forging a consumable electrode for electroslag remelting, after which the resulting electroslag ingot is pressed, hot rolling, pickling and drawing are performed.

1.2. Features

Unlike the known technical solution, which includes smelting ingots, hot rolling of billets obtained from ingots and their further cold rolling; In the claimed technical solution, ingots are melted in a vacuum induction furnace, followed by forging to produce consumable electrodes, their electroslag remelting to produce ingots, which are pressed in one step with a total degree of deformation of 90%, after hot rolling, hot-rolled billets are etched, and cold deformation is carried out by drawing to obtain rods.

At the same time, to ensure the chemical composition, a choice of charge materials is made to ensure the purity of the metal in terms of impurities.

Electroslag remelting of the consumable electrode is carried out in a crystallizer with a diameter of 300-500 mm, and the remelting is carried out according to the mass deposition rate of the ingot depending on the diameter of the crystallizer.

The deformation of the electroslag ingot to the final size of the workpiece is carried out after cooling it in air and subsequent heating according to the regime: planting in a furnace at a temperature of no more than 950°C, holding for no more than 2 hours.

Next, before hot rolling, the billets are heated in two stages according to the following regime: heating at 800°C for at least 45 minutes, then at 950°C for 1-3 hours.

In addition, pickling of hot-rolled rods is carried out in a double acid solution of the following composition, wt. %: NaCl - 3-5, H ₂ SO ₄ - 12-22, H ₂ O - 85-73.

3.3. List of figures and drawings

In fig. Figure 1 shows a photograph of the appearance of hot-rolled rods ∅27 mm of BrKh08 alloy before pickling.

In fig. Figure 2 shows a photograph of the appearance of hot-rolled rods ∅27 mm of BrKh08 alloy after pickling.

In fig. Figure 3 shows a photograph of the appearance of calibrated rods ∅26 mm of BrKh08 alloy.

In fig. Figure 4 shows a photograph of the appearance of turned rods ∅25 mm of BrKh08 alloy.

In fig. 5. A photograph of the appearance of drawn rods ∅21 mm of BrKh08 alloy is presented.

In fig. 6. Photographs of the macrostructure of drawn rods ∅24 mm and ∅21 mm of BrKh08 alloy, selected from two opposite sides of rods numbered 1 and 2, are presented.

4. Description of the invention

Heat-resistant copper-based alloys are characterized by high electrical and thermal conductivity and are used in components designed to operate at elevated temperatures, while maintaining high strength and hardness.

In the claimed technical solution, a consumable electrode is made by forging a copper vacuum ingot obtained by melting charge materials in a vacuum induction furnace (VIF) in a graphite crucible, followed by casting the melt in a protective atmosphere of inert gas.

When smelting copper-based heat-resistant alloys in a high-pressure alloy, there is no contact with the atmosphere; smelting occurs in a graphite crucible either in a vacuum environment or in a “technical vacuum” environment - argon. The deoxidation process is carried out at temperatures up to 1400°C so that the gas and volatile elements can completely evaporate.

Also, to ensure the chemical composition of copper-based heat-resistant alloys, it is necessary to select charge materials that ensure the purity of the metal in terms of impurities. In such alloys, the base is copper, so the key factor in choosing charge materials is the choice of copper grade. Copper grade M00k contains the least amount of impurities, such as hydrogen, oxygen and especially phosphorus, which are most difficult to remove from the melt during vacuum smelting. Also during smelting it is permissible to use chromium of a grade no worse than X99N1, electrolytic nickel of the N-0 grade, metallic titanium of the VT1-00 grade and zirconium iodide.

To obtain a high-quality workpiece for further deformation, a two-stage process is used: consumable electrodes are made, which are then remelted using the electroslag method. The use of electroslag remelting improves the quality of cast metal, improves mechanical characteristics, and reduces the amount of harmful impurities and non-metallic inclusions.

Electroslag remelting of a consumable forged electrode is carried out in a crystallizer with a diameter of 300-500 mm, and the remelting is carried out according to the mass deposition rate of the ingot depending on the diameter of the crystallizer. Table 1 shows the electroslag remelting mode of the manufactured consumable electrode.

After cooling in air, the resulting electroslag ingot is subjected to deformation. To do this, the ingot is heated for deformation according to the following regime: placing it in a furnace at a temperature of no more than 950°C, holding for no more than 2 hours. Pressing is performed in one step with a total degree of deformation of about 90%.

Next, hot rolling is carried out with preliminary two-stage heating of the workpieces according to the following regime: heating at 800°C for at least 45 minutes, then at 950°C for 1-3 hours.

To clean the surface of the resulting hot-rolled rods from scale and increase the service life of the matrices of drawing machines, etching is carried out in a double acid solution of the following composition, wt. %: NaCl - 3-5, H ₂ SO ₄ - 12-22, H ₂ O - 85-73. After which the rods are passed through drawing dies, where the profile and dimensions of the finished product are formed. This technological operation, when compared with rolling, makes it possible to obtain products with higher accuracy of geometric parameters.

The declared technical solution was tested under production conditions at JSC Electrostal Metallurgical Plant with positive results.

Using the proposed method provides:

- obtaining the required chemical composition;

- low content of harmful impurities in the metal;

- accuracy of geometric parameters.

The proposed method makes it possible to produce rods from low-alloy heat-resistant copper-based alloys using traditional metallurgical technologies and standard metallurgical equipment, and also guarantees compliance with the requirements for chemical composition and provides a high level of mechanical properties.

5. Example of method implementation

The method can be implemented on a complex installation of standard metallurgical equipment:

- the alloy is smelted in a vacuum induction furnace of the ISV series, with a capacity of 1.0 t and/or 2.5 t, with a graphite crucible installed in the inductor;

- free forging of consumable electrodes for electroslag remelting (ESR) is carried out on a radial forging machine (RKM) or on a 16MN forging press;

- mechanical treatment of the surface of the prepared consumable electrode;

- ESR of consumable electrodes into a crystallizer ∅320 mm or ∅425 mm;

- deformation of an electroslag ingot on a 16MN forging press into a workpiece for hot-rolled steel;

- hot rolling on a 350/250 mill;

- pickling and drawing of hot-rolled rods.

An ingot ∅320 mm of low-alloy heat-resistant alloy BrKh08, obtained by electroslag remelting of a consumable electrode of vacuum induction smelting (the chemical composition is given in Tables 2 and 3), was deformed in one step onto a workpiece ∅95 mm. After preliminary two-stage heating, the workpieces were hot rolled to a size of ∅27 mm.

The appearance of hot-rolled rods ∅27 mm of BrKh08 alloy before and after pickling is shown in Fig. 1 and 2, respectively.

The production of drawn rods ∅24 mm and ∅21 mm from BrKh08 alloy was carried out according to the following schemes:

Scheme 1: hot-rolled ∅27 mm → etching → calibration ∅26 mm → turning ∅25 mm → drawing, ∅24 ^-0.21 mm.

Scheme 2: hot-rolled ∅27 mm → etching → calibration ∅26 mm → turning ∅25 mm → drawing ∅23 mm → drawing ∅21.0 ^-0.21 mm

The appearance of calibrated rods ∅26 mm and turned rods ∅25 mm of BrKh08 alloy is shown in Fig. 3 and 4, respectively. In fig. 5. The appearance of drawn rods ∅21 mm of BrKh08 alloy is presented.

To study the macrostructure of drawn rods ∅24 mm and ∅21 mm, samples 30 mm long were selected from two opposite sides of the rods, marked with numbers 1 and 2. The macrostructure is presented in Fig. 6. On all samples, metal from the surface to a depth of has a crystalline structure with a characteristic luster. There are no defects in the form of shells, inclusions, delaminations, etc., visible without the use of magnifying devices.

Additionally, ultrasonic testing was carried out on drawn rods of BrKh08 alloy. Ultrasound examination revealed no defects ≥3 mm.

The mechanical properties of BrKh08 alloy rods ∅24 mm and ∅21 mm were tested on heat-treated samples at 20°C in accordance with TU 48-21-197. The control results meet the requirements and are shown in Table 4.

The declared technical solution was tested under production conditions at JSC Electrostal Metallurgical Plant with positive results. The proposed solution ensures the required chemical composition and low content of harmful impurities. The mechanical properties of drawn rods of BrKh08 alloy in sizes ∅24 mm and ∅21 mm meet the requirements.

Thus, the proposed method makes it possible to produce rods from low-alloy heat-resistant copper-based alloys using traditional metallurgical technologies and standard metallurgical equipment, and also guarantees compliance with the requirements for chemical composition and provides a high level of mechanical properties.

Claims (3)

1. A method for manufacturing rods from BrKh08 bronze, including the smelting of BrKh08 bronze ingots, hot rolling of billets obtained from the ingots and their further cold deformation, characterized in that the ingots are smelted in a vacuum induction furnace, followed by their forging to obtain consumable electrodes, their electroslag remelting to produce ingots, which are pressed in one step with a total degree of deformation of 90%; after hot rolling, the hot-rolled billets are pickled, and cold deformation is carried out by drawing to produce rods. 2. The method according to claim 1, characterized in that before hot rolling, the workpieces are heated in two stages according to the following regime: heating at 800°C for at least 45 minutes, then at 950°C for 1-3 hours. 3. The method according to claim 1, characterized in that the pickling of hot-rolled billets is carried out in a double acid solution of the following composition, wt.%: NaCl - 3-5, H ₂ SO ₄ - 12-22, H ₂ O - 85-73.