RU2808615C1 - METHOD FOR MANUFACTURING RODS WITH DIAMETER OF 8-60 mm FROM LOW-ALLOYED HEAT-RESISTANT COPPER-BASED ALLOYS - Google Patents

Abstract

FIELD: rolling mill.

SUBSTANCE: used for hot rolled section of rods with a diameter of 8-60 mm from low-alloy heat-resistant copper-based alloys, subject to turning and suitable for the manufacture of products used at elevated temperatures. The method includes multi-pass hot rolling of a previously obtained pressed blank with a diameter of 95-100 mm, to pre-finishing sizes in the temperature range 950-700°C on calibration “circle-oval-circle” with reductions per pass of 5-40% and a total degree of reduction of 50-99%, followed by cutting to final dimensions.

EFFECT: possibility of expanding the range of rods, increasing productivity, reducing the production cycle of rods, reducing metal consumption and increasing the environmental friendliness of the process.

3 cl, 1 tbl, 1 ex

Description

1. Technical field

The invention relates to rolling production, and can be used for hot section rolling of rods with a diameter of 8-60 mm from heat-resistant copper-based alloys, subject to turning and suitable for the manufacture of products used at elevated temperatures.

2. Prior art

The well-known “Method for the production of long products” (patent RU 2291205, class C21D 8/06, C22C 38/14, published 01/10/2005), including heating the billet to 1100-1280 ° C, subsequent multi-pass hot rolling with compression in rolls with gauges with a rolling end temperature in the range of 950-1100°C and cooling with water to 850-950°C, and when using a rolled billet, multi-pass rolling is carried out with a total stretch of at least 16, and when using a cast billet - with a total stretch of at least 36.

The disadvantage of this known method is that it is not suitable for objects made of low-alloy heat-resistant copper-based alloys.

The “Method for the production of high-quality profiles” is known (patent RU 2243834, class B21B 1/46, published 01/10/2005). The method includes heating a continuously cast steel billet to the austenitization temperature and subsequent multi-pass hot rolling with a regulated end-of-rolling temperature. In this case, multi-pass rolling is carried out with a rolling end temperature of 860-1000°C and a total drawing X regulated by the steel group.

The disadvantages of the known method are that the wire rod, especially with a diameter of 8-10 mm, has low technological ductility and uneven mechanical properties across the cross-section, and is also not suitable for rolling copper-based alloys.

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 the sections and the yield; moreover, the method is not suitable for rolling low-alloy heat-resistant copper-based alloys.

Also known, accepted by the applicant as the closest analogue, is “Method of thermal deformation processing of products made of chrome bronze” (patent RU 2327807, class C22F 1/08, published on June 27, 2008), including the production of rod blanks by hot pressing through a matrix with a channel, their quenching in water, drawing finished rods to final dimensions and subsequent aging.

The disadvantages of this method include high labor costs.

3. Essence of the invention

3.1. Statement of technical problem

The technical objective of the claimed invention is to ensure a stable level of mechanical characteristics, as well as increase productivity by reducing the number of auxiliary operations.

The result of solving a technical problem

The solution to the stated technical problem is achieved by multi-pass hot rolling of a pressed billet of 095-100 mm to pre-finishing dimensions, followed by turning to finishing dimensions of 08-60 mm. Rolling is carried out in the temperature range of 950-700°C on a circle-oval-circle calibration with reductions per pass of 5-40% and a total reduction degree of 50-99%. As a result, the following is achieved: expansion of the range of rods, increased productivity, reduction of the production cycle for manufacturing rods, reduced metal consumption and increased environmental friendliness of the process.

3.2. Features

In contrast to the known technical solution, which includes obtaining a workpiece and its further thermal deformation processing; In the claimed technical solution, multi-pass hot rolling of a previously obtained pressed billet of 095-100 mm is carried out to pre-finishing dimensions in the temperature range of 950-700 ° C on a circle-oval-circle calibration with reductions per pass of 5-40% and a total degree of reduction of 50- 99%, followed by cutting to final dimensions.

In this case, the deformation of an ingot made of a heat-resistant copper-based alloy to a final workpiece size of 095-100 mm is carried out in one step with a total degree of deformation of about 90% after heating it according to the regime: planting in a furnace at a temperature of no more than 950°C, holding for no more than 2 hours.

Then the resulting workpieces are machined until defects are removed.

In addition, 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.

4. Description of the invention

The claimed technical solution considers the possibility of manufacturing rods from heat-resistant alloys on a copper base from a cast ingot obtained either by open smelting or vacuum smelting with or without subsequent electroslag remelting.

The deformation of an ingot from a low-alloy heat-resistant copper-based alloy to a final billet size of 095-100 mm is carried out after it is heated according to the following regime: planting in a furnace at a temperature of no more than 950°C, holding for no more than 2 hours. Then the ingot is pressed in one step with a total degree of deformation of about 90%, after which the resulting blanks are machined until defects are removed.

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

When the rolling start temperature of the pressed billet is above 950°C, oxidation of the grain boundaries occurs during the heating process. A decrease in the rolling start temperature below 850°C leads to a loss of ductility in the last passes, which reduces the quality of the rods and the yield.

Next, multi-pass hot rolling of pressed billets 095-100 mm is carried out in the temperature range 950-700°C on a circle-oval-circle calibration with reductions per pass of 5-40% and a total reduction degree of 50-99%. Then the turning is performed. The range of hot-rolled rods produced is from a circle of 8 mm to a circle of 60 mm.

Rolling in calibers at temperatures of 950-700°C is accompanied by the development of dynamic recrystallization and the formation of a structure with a grain size of less than 10 microns. Increasing the rolling temperature will lead to excessive ductility and create problems with the passage of metal in the mill line and with ensuring the required rod sizes. A decrease in temperature will contribute to the hardening of copper alloys and a decrease in their technological ductility.

It has been experimentally established that cooling rolled rods below a temperature of 700°C does not exclude the formation of defects in the rods due to loss of ductility, and also does not provide the required set of mechanical properties. This deteriorates the quality of the rods and the yield of suitable rolled products.

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

Using the proposed method allows you to:

- produce rods from low-alloy heat-resistant copper-based alloys using traditional metallurgical technologies and standard metallurgical equipment;

- reduce the production cycle of rods by eliminating technological operations such as intermediate annealing, etching and drawing to the required size;

- increase the environmental friendliness of the rod manufacturing process by eliminating the etching operation used to clean the surface of the rods from scale;

- ensure the accuracy of geometric parameters;

- ensure a high level of mechanical properties.

b. Example of method implementation

After heating in a chamber furnace, melted and prepared ingots from a heat-resistant copper-based alloy BrKh08 were pressed onto a round billet with a diameter of 0100 mm. Then the resulting workpieces were cut to size 096 mm. Next, the processed workpieces were heated in a two-stage mode: heating at 800°C for 55 minutes, then heating at 950°C for 92 minutes. Then hot rolling was carried out using circle-oval-circle calibration to sizes 045 mm and 027 mm with a total reduction degree of 78 and 92%, respectively.

In order to compare the quality of hot-rolled and cold-drawn metal, rods were drawn from 027 mm to 024 mm and 021 mm. In this case, the 027 mm rods were etched and calibrated at 026 mm, then turned at 025 mm and calibrated at 024 mm (total deformation 15%) and 021 mm (total deformation 35%). Rods 045 mm were ground to a finishing size of 043 mm.

A study of the macrostructure in the transverse direction of the resulting rods did not reveal any defects in the form of shells, inclusions, delaminations, etc., visible without the use of magnifying devices. Additionally, ultrasonic testing was carried out on the rods of the BrKh08 alloy. No defects were found during ultrasonic testing.

The mechanical properties of BrKh08 alloy rods 045 mm, 027 mm, 024 mm, 021 mm were tested at 20°C in the delivered state and on heat-treated samples in accordance with TU 48-21-197. The control results are shown in Table 1.

Table 1. Results of mechanical properties testing. Size, mm State Use temperature, °C Mechanical properties Type of heat treatment bv, N/mm ² δ,% 045 g/k 20 266-270 41-47 No heat treatment 027 g/k 20 259-261 45-52 024 Hard-worked (E~15%) 20 284-289 26-31 021 Hard-worked Œ~35%) 20 360-362 15-18 045 g/k 20 348-353 28-31 980°С, 0.5 h, water+450°С, 5 h, air 027 g/k 20 404-440 17-28 024 Hard-worked (E~15%) 20 356-393 18-20 021 Hard-worked (E~35%) 20 351-417 19-29 ND requirements 20 >340.0 >12.0 980°С, 0.5 h, water+450°С, 5 h, air

The results obtained show that metal of different initial states (hot-rolled and cold-drawn) after heat treatment of the samples according to the regime of 980°C, 0.5 h, water +450°C, 5 h, air has the same type of properties that meet the requirements of the ND.

The declared technical solution was tested under production conditions at JSC Electrostal Metallurgical Plant with positive results. The method makes it possible to shorten the production cycle of rods by eliminating technological operations such as intermediate annealing, etching and drawing to the required size, which additionally leads to an increase in the environmental friendliness of the rod manufacturing process.

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

Claims (3)

1. A method for manufacturing rods with a diameter of 8-60 mm from heat-resistant copper-based alloys, including obtaining a workpiece and its further thermal deformation treatment, characterized in that multi-pass hot rolling of a previously obtained pressed workpiece with a diameter of 95-100 mm is carried out to pre-finishing sizes in the temperature range of 950 -700°C for circle-oval-circle calibration with reductions per pass of 5-40% and a total degree of reduction of 50-99%, followed by cutting to final dimensions. 2. The method according to claim 1, characterized in that the deformation of an ingot from a heat-resistant copper-based alloy to the final size of the workpiece with a diameter of 95-100 mm is carried out in one step with a total degree of deformation of about 90% after its heating according to the mode: landing in a furnace at temperature no more than 950°C holding time no more than 2 hours. 3. 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.