RU2437943C1 - Procedure for quenching long-length metal items - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: item is heated and tempered at low temperature. Also, the long-length item is continuously transferred on a transporter at rate 3-10 mm/sec. The item passes through a local zone of heating with alternative electro-magnetic field of 8-20 kHz frequency. In the local zone the item is heated to temperature 800-1000C. Further tempering is performed to temperature 300-200C. Local intensive cooling with a jet of compressed air facilitates formation of martensite structure of metal, where upon temperature of the item is brought to temperature of environment. ^ EFFECT: high efficiency and manufacture of items with different strength characteristics along section. ^ 2 cl, 1 dwg

Description

The invention relates to the field of engineering, and in particular to methods of heat treatment of long metal products, in particular when hardening knives for road machines designed to clean the road surface.

The known method of continuous heat treatment of long steel products [1], including heating the product in an oxidizing atmosphere to an austenitizing temperature, accelerated cooling to a predetermined temperature, isothermal aging and final cooling, while accelerated cooling is carried out to a temperature of minimum stability of supercooled austenite, at this temperature plastic deformation with a compression ratio of 1-20% using a die while simultaneously pressing a graphite layer with oyannoy load of 20-200 kg / mm ^2, and then carried out isothermally at a temperature of 20 ° C above the start of martensite transformation of the steel, but below 650 ° C with application of a tensile force constituting 10,5-1,0 yield strength.

The disadvantage of this method is the complexity of its implementation, due to the need for plastic deformation of the product and the need to use a layer of graphite.

The closest in technical essence to the proposed technical solution is a known method of hardening steel parts [2], which includes heating the parts to austenitic temperature, cooling moving parts in a quenching tank with at least two quenching media with different densities, not miscible with each other and located in the direction of movement of the parts, while the location of the quenching media in the direction of movement of the parts in the quenching tank and the speed of movement of the parts are preliminarily determined by the cooling method the volume of liquids and the necessary curve for the hardening of parts.

The closest analogue [2] requires a cooling operation in two quenching media with different densities to monitor the cooling ability of liquids, which determines the necessary speed of parts, which complicates the technical implementation.

Known methods of hardening long-sized parts provide volumetric hardening of metal with cooling in liquid media and do not allow to obtain products with different strength characteristics in cross section, which is required, for example, in the manufacture of knives with hardened edges intended for contact with the road surface. In addition, for heat treatment of products by known methods requires a significant amount of thermal energy and large volumes of cooling media (liquids).

The technical result, which consists in eliminating the noted drawbacks of the prototype, is achieved in the proposed method of hardening of long metal products based on heating the product and subsequent low-temperature tempering, in that the long product is continuously moved on a conveyor at a speed of 3-10 mm / s with the passage of the product through a local heating zone with an alternating electromagnetic field with a frequency of 8-20 kHz, ensuring the heating of the product in the local zone to a temperature of 800-1000 ° C, and subsequent tempering is carried out they are heated to a temperature of 300-200 ° C with the formation of a martensitic metal structure by local intensive cooling with a jet of compressed air, after which the product temperature is brought to ambient temperature, and the stream of cooling compressed air is directed mainly to areas of the metal product intended for mechanical contact with external environments.

The essence of the proposed method is illustrated in the drawing, which shows a functional diagram of the device with which the method of hardening of long (extended) metal products, for example, knives for road harvesting machines, is carried out.

The proposed method is carried out in the following way.

A long-sized product 1 ₁ (for example, a steel plate) is placed on the conveyor 2 and continuously moved at a speed of 3-10 mm / s.

When moving the product falls into the zone 1 _{2 of the} impact of the device 3, generating an electromagnetic alternating field created by a high frequency current with a frequency of 8-20 kHz. The selected frequency range is determined experimentally. The specific frequency depends on the material and the geometric dimensions of the product (thickness, width, length).

When this occurs, the heating of part 1 ₂ in the local zone to a temperature of 800-1000 ° C (temperature of the product at various points on the surface). Inductors (not shown) of the device 3 are arranged so that the heating occurs mainly in the corresponding local areas, for example, along the edge of the plate of the product 1 ₂ . This saves energy on heating.

Next, the product 1 ₃ is cooled to a temperature of 300-200 ° C (the temperature range is determined experimentally) to ensure the formation of a martensitic metal structure by means of local intensive cooling with a stream of compressed air using device 4.

In this case, a stream of cooling compressed air from the device 4 (compressor) is directed mainly to the sections of the metal product 1 ₃ intended for mechanical contact with external media. This leads to faster cooling of selected local sections of the metal product, which contributes to their hardening.

At the final stages 1 ₄ , the product is dispensed and the temperature of the product 1 _{5 is} brought to ambient temperature, and the product is transferred to the next production technological section for machining.

The proposed method provides low thermal energy costs for heating, high productivity and the ability to obtain parts after hardening with different strength indicators for the cross section of the part, for example: with hardened edges and a soft core, which facilitates machining, for example, when drilling mounting holes.

The proposed method is used in the technological process for the manufacture of knives from wear-resistant steel in a wide range of geometric parameters for various types of road mechanisms and machines.

Information sources

1. RF patent No. 2087555, IPC C21D 9/52 of 01/10/1995.

2. RF patent No. 2222609, IPC C21D 1/56, C21D 1/25, C21D 1/63 of 02/14/2001.

Claims (2)

1. The method of hardening of long metal products, including heating the product and subsequent low-temperature tempering, while the long product is continuously moved on a conveyor at a speed of 3-10 mm / s with the passage of the product through the local heating zone with an alternating electromagnetic field with a frequency of 8-20 kHz with heating the product in the local zone to a temperature of 800-1000 ° C, and subsequent tempering is carried out to a temperature of 300-200 ° C with the formation of the martensitic structure of the metal by local intensive cooling jet of compressed air, and then bring the temperature of the product to ambient temperature. 2. The method according to claim 1, in which the stream of cooling compressed air is sent mainly to areas of the metal product intended for mechanical contact with external media.

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