RU2320735C2 - Method for electroslag production of die blanks for pressing-rolling line for production of railway wheels - Google Patents

Abstract

FIELD: special electric metallurgy, in particular, process used in enterprises for manufacturing and/or utilizing of processing technique for hot plastic working of metals.

SUBSTANCE: method involves providing process in melting space of crystallizer having shape approximating in maximum extent to shape of die blank; melting metal and heating flux using current conductive consumable electrodes made from blank metal and disposed circumferentially within melting space with filling coefficient of at least 0.2, with total weight of electrodes being at least equal to that of blank; conducting process with value of supplied power being constant up to time when shrink hole is removed. Method allows die blanks of desired sizes and shapes to be produced with maximum high metal recovery of 0.8-0.9.

EFFECT: increased efficiency in producing of die blanks for railway wheels.

3 cl, 3 ex

Description

The invention relates to special electrometallurgy and can be used at enterprises manufacturing and / or operating technological equipment for hot metal forming.

Features of the operation of the dies of the press rolling line (PPL) are associated with the presence of high-speed presses with increased power. Quick-flowing thermodynamic alternating loads, significant heating of the working surface, the effect of a special coolant place high demands on the quality of the metal of the die blanks, which largely determines the operational stability of the stamps.

In addition, the special geometry of the PPL pressing tool, which is a large solid and hollow ingot with a height to diameter ratio of more than 1: 3.5 (“short” ingots), combined with an increased die weight (more than 0.8 t) suggests difficulty receiving blanks for the tool.

The traditional technology for producing workpieces of a deformation tool includes steelmaking in a metallurgical unit, casting into ingots and forging them into workpieces with permitted tolerances for further heat and machining.

The process is characterized by a low metal utilization coefficient (KIM <0.5) as a result of metal losses at all stages and the presence of an expensive forging operation that ensures the shape of the tool and sufficient metal quality of the product.

In the manufacture of PPL dies using this technology, the cost of manufacturing blanks increases due to the need to use specialized powerful equipment. In some cases, it is also impossible to obtain blanks of the desired geometry in combination with satisfactory metal quality.

There is an improved technology for the preparation of deformation tool blanks, according to which modern semi-continuous casting machines are used instead of casting metal into ingots.

The utilization of metal in this case increases to 0.50-0.55. However, the design capabilities of machines do not allow to obtain the necessary range of sizes of blanks.

In addition, the quality of the workpiece metal still has to be forged or drafted. At the same time, the above-mentioned disadvantages of the technology associated with an increase in the mass and size of the workpiece are preserved.

A known method for producing hollow ingots electroslag surfacing (RF Patent No. 2190029, publ. 2002). The method is intended for electroslag production of hollow ingots of a given size in a melting space formed by two water-cooled crystallizers placed coaxially in one another.

Surfacing is carried out under a liquid flux, the melting and heating of which is carried out by non-consumable, non-consumable graphite electrodes. At the same time, the quality of the ingot, the chemical composition of the metal and its constancy are ensured by the rotation of the melting zone in combination with a system for feeding into it and regulating the amount of liquid and granular materials. In this method, non-consumable, non-consumable graphite electrodes do not perform the function of melting the metal, but rather contribute to the melting of the flux and its maintenance in a liquid state.

The known method cannot be used to obtain large "short" ingots, because it is technically difficult to rotate a water-cooled melting space with a diameter of more than 700 mm with liquid high-temperature components (metal and slag) weighing more than a ton.

The use of graphite non-consumable electrodes is also inapplicable due to carburization of pre-eutectoid die steels containing carbide-forming alloying chemical elements through molten slag and the inability to obtain guaranteed performance properties of PPL dies. In addition, it is irrational to have a large capacity intermediate device separate from the melting zone for melting and storing liquid metal.

The objective of the present invention is to develop an effective method for producing high-quality electroslag blanks of dies for a press-rolling line for the production of railway wheels of various sizes.

For these purposes, the method of electroslag production of die blanks involves placing current-carrying consumable electrodes from the metal of the workpiece, the total weight of which is not less than the weight of the workpiece, around the circumference in the melting space of the mold with a fill factor of at least 0.2, fusion of the consumable electrodes under a liquid flux, the formation of an ingot under liquid flux, in this case, the process is conducted at a value of input power that is constant until the shrink shell is removed, and the shape of the melting space is as close as possible ene to form a preform die.

To implement the method, current-carrying consumable electrodes of tool die steel of a given chemical composition and a certain size and weight are used.

The novelty of the proposed method lies in the development of the progressive method of ESR in the application to such a type of products as PPL dies having special operating conditions, special geometry and various sizes.

In the inventive method, consumable electrodes of tool die steel of a given chemical composition are a source of consumable metal and, having a weight of at least the weight of the workpiece, are involved in the "organization" of obtaining workpieces of various sizes.

In conjunction with the shape of the mold melting space, which is as close as possible to the shape of the tool blank, the method allows you to obtain blanks of the required sizes and shapes with the highest possible CMM (0.8-0.9).

The location of the consumable electrodes around the circumference in the melting space with the optimal fill factor and the process with the input power constant until the withdrawal of the shrink shell allows directional crystallization of the metal from a small volume of the liquid metal bath and to ensure high quality of the resulting “short” billet, minimizing segregation and foundry defects in steel.

A new technical result achieved by the claimed method is to increase the utilization of metal, obtaining high-quality "short" large blanks of various sizes and special shapes.

Thus, the organization of the process in a single melting space in the manner described above allows you to get the whole range of standard sizes of high-quality PPL dies with minimum costs and the highest metal utilization rate.

The method was tested in an industrial environment at one of the enterprises having the appropriate equipment. To implement the method, consumable electrodes obtained by any method were used, which are metal rods of a certain size and weight from tool die steels, which allows you to gain the weight of workpieces of any standard size and provides the necessary fill factor.

The electrodes were arranged around the circumference in the melting space of the mold.

Example 1. To obtain a hollow billet with an outer diameter of 1000 mm, an inner diameter of 245 mm and a height of 220 mm in a water-cooled melting space formed by a crystallizer and placed in it with a coaxial mandrel insert, 8 consumable electrodes with a section of 170 × 120 mm were simultaneously fused under a liquid flux , with a total weight of 1.3 tons. With a fill factor of 0.2 and an input power of 1120 kVA, the consumable electrodes were completely melted in 125 minutes of the process and a workpiece weighing 1.27 t was obtained with a metal utilization factor of 82.

Example 2. To obtain a hollow billet with an outer diameter of 780 mm, an inner diameter of 245 mm and a height of 225 mm in a water-cooled melting space formed by a crystallizer and placed in it with a coaxial mandrel insert, 6 consumable electrodes with a section of 170 × 120 mm and a total weight of 0.7 t were simultaneously melted under a liquid flux.

With a fill factor of 0.34 and an input power of 814 kVA, the consumable electrodes were completely melted in 68 minutes of the process and a workpiece weighing 0.63 tons was obtained with a metal utilization factor of 0.87.

Example 3. To obtain a solid with an outer diameter of 1000 mm, an inner diameter of 245 mm and a height of 250 mm in a water-cooled melting space formed by a mold without a mandrel, 12 consumable electrodes with a section of 170 × 120 mm and a total weight of 1.53 t were simultaneously melted under a liquid flux .

With a fill factor of 0.31 and an input power of 1620 kVA, the consumable electrodes were completely melted in 95 minutes of the process and a workpiece weighing 1.53 tons with a metal utilization factor of 0.92 was obtained.

The technical means of realizing the constant input power until the shrinkage shell is removed in all the examples is the stationary melting mode known in the ESR.

Operational testing of dies obtained from electroslag billets was carried out on a press-rolling line for the production of railway wheels. The resistance of the stamps made by the present method is 1.8 times higher than a similar stamp produced by technology.

Claims (3)

1. The method of electroslag production of die blanks for a press rolling line for the production of railway wheels, comprising placing current-carrying consumable electrodes from the metal of the workpiece, the total weight of which is not less than the weight of the workpiece, around the circumference in the melting space of the mold with a fill factor of at least 0.2, fusion of the consumable electrodes under liquid flux, the formation of an ingot under the liquid flux, while the process is carried out at a value of input power, constant until the withdrawal of the shrink shell, melting space of the mold form as close to the shape of the preform die. 2. The method according to claim 1, in which current-carrying consumable electrodes of tool die steel of a given chemical composition are used. 3. The method according to claim 1, in which current-carrying consumable electrodes of a certain size and weight are used.