RU2405843C1 - Method for making high-quality instrument steels from wastes of instrument manufacture - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves remelting of lump scrap of instrument steel in electric furnace so that consumable electrodes are obtained and their further remelting in electroslag remelting plant at simultaneous continuous supply of instrument steel chips of similar chemical composition to melting zone is performed.

EFFECT: invention allows melting ingots of instrument steel only from lump scrap and chips of instrument steels of the required chemical composition with increased level of physical and mechanical properties and operating characteristics.

1 ex, 1 dwg

Description

Criticism of analogues and prototype

The rational use of waste generated at tool and machine-building plants is a major problem. At the same time, out of the total amount of waste arriving at Vtorchermet's bases, up to 70% is accounted for by shavings. The cost of a rolled profile of the most common high-speed steel P6M5 is only 2.7-3.2 times higher than the price of chips, which necessitates the efficient use of the resulting lump and chip waste for the production of gauge metal.

The existing technology for processing lump and chip waste of tool steels is multistage and is associated with high energy consumption: a small-sized charge is melted in electric arc furnaces and poured into charge ingots, which are then used already for smelting steel. At this redistribution, the total waste of the charge is 6-12%, including tungsten on average 15%, vanadium - 30%, molybdenum - 10%. It should be borne in mind that chips with a low bulk density are not compacted at most plants, which leads to an increase in transportation costs and its loss during transshipment and storage [1, 2].

The casting of high-speed steels into relatively small ingots, weighing up to 1000 kg, causes significant metal loss to the edge and does not provide high quality steel.

An analysis of the currently used methods for the production of high alloy steels, such as induction and electric arc melting, electroslag remelting, indicates the advantages of the latter method, which can provide:

- insignificant fumes of the main alloying elements of high-speed steels, which excludes additional doping during metal remelting of a final chemical composition;

- defect-free surface of ingots that does not require stripping before deformation;

- high chemical and structural homogeneity of the metal with a low content of impurities and gases;

- increased yield of the product due to increased deformability of the ingot and lower head and bottom trim;

- the best complex of physico-mechanical properties compared to conventional smelting metal.

Due to the fine microstructure and uniform distribution of the carbide phase, chemical uniformity and purity, high-speed steel of electroslag smelting has higher ductility than steel of ordinary smelting. The yield for forging, for example, of electroslag ingots of PI8 steel is 80-93%, instead of 60-70% for ingots of conventional smelting [3].

The described advantages of tool steels smelted using the ESR method apply only to the use of compact (cast or deformed) consumable electrodes. Such material as chips, characterized by increased contamination, developed specific surface area, low bulk density, can make significant adjustments to the smelting technology. The connection between the quality of the metal and the technology of its smelting seems obvious, therefore, the choice of a rational scheme of chip ESR is of fundamental importance.

The objective of the invention is the production of high quality tool steel, based on the full (100%) use for the smelting of scrap and chip steel.

To solve this problem, steelmaking uses tool production waste, 100% consisting of a start bed and shavings, while melting it in an electric furnace of lump scrap of tool production to produce consumable electrodes and their subsequent remelting in an electroslag remelting unit with simultaneous continuous supply to the zone melting chips of instrumental production of a similar chemical composition.

The following flow chart is proposed for the production of tool steels using lumpy waste and shavings generated in tool production:

1. Remelting in the electric arc or induction furnace of lumpy waste of tool production with the necessary bringing the melt by additional alloying to the required chemical composition, for example, steel P6M5.

2. Casting of melted P6M5 steel into a chill mold to obtain a consumable electrode for subsequent electroslag remelting.

3. Remelting of the consumable electrode at the ESR unit, which allows simultaneously feeding chips of tool steel (for example, the same steel P6M5) into the melting zone and remelting to obtain a final chemical composition (for example, diameter up to 125 mm) of the finished ESR ingot (for example, steel P6M5).

For the implementation of electroslag remelting of tool chips, a design of the ESR installation is proposed, the schematic diagram of which is shown in the drawing.

From the hopper 1, the chips along the inclined chute 2 through the intermediate funnel 3 are fed to the weighing batcher 4, and then through the vibratory funnel of the batcher 5 it enters the mold 8, where it is melted by the electrode 6. To supply the chips to the crystallizer, for example, a weighing batcher DN -21U with belt feeder. Chip dosing performance can vary between 30-160 kg / h.

The installation for ESR chips can be mounted on the basis of a serial apparatus for electroslag welding and surfacing A - 550C with power sources - single-phase transformers TSD - 2000.

It is possible to produce remelting in diam. 125 mm sq. 125 mm, slider 120 × 180 mm.

For remelting, dia electrodes can be used. 40-60 mm.

At the same time, to obtain a quality ingot, the amount of chips used for remelting should not exceed 60-70% of the mass of the obtained ESR ingot.

An example of the method

The proposed technology was implemented on a standard electroslag furnace type A-550, equipped with a dosing and supply chip system (in accordance with the drawing). Smelting of steel P6M5 was carried out in an ESR mold of diameter. 125 mm using cast electrode dia. 50 mm, melted in an electric arc furnace using 100% lumpy waste of tool production and the introduction of P6M5 steel shavings from the batcher during remelting.

Below are the test results of the obtained metal:

Chemical composition

The content of elements,% FROM W Mo Cr V Shavings 0.91 6.1 5.2 4.1 2.0 ESR ingot 0.92-0.95 5.75-5.85 4.8-4.95 4.0 1.85-1.90

Properties of forged steel P6M5

Hardness of hardened and tempered steel, HRc Bending strength, MPa Beats viscosity, kJ / m ² 62-64 3130-3230 245-274

Electroslag high-speed steel P6M5, obtained by remelting chips, is characterized by the absence of defects of liquation origin, a dense defect-free macrostructure, microcrystalline structure and structural homogeneity.

Comparative tests of the tool (drill with a diameter of 20 mm) made of standard steel P6M5 for electric arc smelting and steel obtained by electroslag remelting of chip P6M5 were carried out. 10 drills were manufactured and tested in the processing of steel from 40X steel.

Under similar cutting conditions, the average resistance of the experimental drill between regrinding was 200 minutes, standard - 190 minutes.

Thus, the proposed method of electroslag remelting of chips allows producing tool steel that fully meets all the requirements for serial tool production.

Literature

1. Ivanov V.G. and others. Remelting shavings of high-speed steels. Metallurgist. 1975. No4, p.25-26.

2. Stroganov A.I. et al. Losses of tungsten in the production of high speed steel. Metallurg, 1971. No. 1, pp. 30-33.

3. Moshkevich L.D. and others. On the quality of high-speed steel electroslag remelting. Steel, 1977. No. 3., S. 219-233.

Claims (1)

A method of smelting a tool steel ingot from tool production waste, characterized in that the waste is 100% melted out of lump scrap and tool steel shavings, while the tool steel lump is remelted in an electric furnace to produce consumable electrodes, which are then remelted in the installation electroslag remelting with simultaneous continuous supply of tool steel with a similar chemical composition to the melting zone.

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