JPH0734139A - Continuous heat treatment device for improving descaling property - Google Patents

Abstract

PURPOSE:To provide a heat treatment device which continuously heat treats works, such as coiled wires, and is so improved as to make the scale generated on their surfaces easily removable. CONSTITUTION:This continuous heat treatment device consists of a continuous atmosphere furnace 1 in which a reducing atmosphere is maintained the works 4, such as wires, are continuously carried therein and are subjected to prescribed heat treatments, such as heating and soaking, an oxidizing chamber 9 into which the works taken out of the continuous atmosphere furnace 1 are charged and air is introduced and a cooling chamber 13 which rapidly cools the works 4 taken out of the oxidizing chamber 9 by blast.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment apparatus for continuously heat-treating a treated product such as a wire wound in a coil shape and improving so that scales generated on the surface of the product can be easily removed.

[0002]

2. Description of the Related Art When a steel material such as a hot rolled bar material or a wire coil is further subjected to high-dimensional plastic working such as wire drawing or cold forging, the steel material is kept in, for example, a reducing atmosphere before the working. It is annealed by heating and soaking in a predetermined process in a heat treatment furnace.

By the way, a scale is generated on the surface of the steel material after the heat treatment, and if the above-mentioned processing is performed while the scale is adhered, the die is significantly worn or the scale is hard to be ground and the quality is deteriorated. The steel material after heat treatment is descaled by a chemical method such as pickling or a mechanical method such as shot blasting.

[0004]

When the steel material is taken out from the atmospheric heat treatment furnace at about 650 ° C. and left in the atmosphere, wustite (F _e O) is generated on the surface of the steel material, and the wustite is magnetite (F _{e 3} O ₄ ), hematite (F
_e2 O ₃ ). Therefore, on the surface of the steel material, a wustite layer, a magnetite layer,
A scale consisting of a hematite layer is formed.

When cooled slowly, a part of the wustite layer near the base steel interface transforms into magnetite and iron. When gradually cooled in the atmosphere in this way, hard magnetite precipitates with wustite on the surface of the steel material and the magnetite does not easily dissolve even by pickling, and it does not easily fall off even by a mechanical method such as shot blasting. The descaling property becomes extremely poor.

[0006]

The present invention has been made in view of the above problems, and an object thereof is to provide a continuous heat treatment apparatus in which descaling of a steel material is further improved. for that reason,
The present invention relates to a continuous atmosphere furnace that continuously conveys a processed product such as a wire rod into a furnace kept in a reducing atmosphere, heats and soaks it to perform a predetermined heat treatment, and a treatment taken out from the continuous atmosphere furnace. It is characterized by comprising means for oxidizing the surface of the product and a cooling chamber for rapidly cooling the processed product whose surface is oxidized. Further, according to the present invention, a continuous atmosphere furnace in which a treated product such as a wire is continuously conveyed into a furnace kept in a reducing atmosphere and heated, soaked and subjected to a predetermined heat treatment, and a continuous atmosphere furnace taken out from the continuous atmosphere furnace. It is characterized in that it comprises an oxidation chamber in which a treated product is charged and an oxidizing gas is introduced into the chamber, and a cooling chamber for rapidly cooling the treated product taken out from the oxidizing chamber.
Further, according to the present invention, a continuous atmosphere furnace in which treated products such as wire rods are continuously conveyed into a furnace kept in a reducing atmosphere to heat, soak and perform a predetermined heat treatment, and the continuous atmosphere furnace is taken out from the continuous atmosphere furnace. It is characterized in that it comprises a cooling chamber for rapidly cooling the processed product, and the continuous atmosphere furnace and the cooling chamber are connected by a transfer means. Further, the present invention continuously conveys a processed product such as a wire rod into a furnace kept in a reducing atmosphere and heats it.
A continuous atmosphere furnace for soaking and performing a predetermined heat treatment, and a cooling chamber for rapidly cooling the processed product taken out from the continuous atmosphere furnace, and an oxidizing gas was introduced into the cooling chamber. Was featured. Furthermore, the present invention is characterized in that the temperature of the processed product in the oxidation chamber is maintained at 700 to 560 ° C. and air is introduced. Further, the present invention is characterized in that the treated product is cooled in the cooling chamber at least in the range of 560 ° C to 350 ° C at a cooling rate of 8 ° C / min or more.

[0007]

The steel material taken out from the atmosphere heat treatment furnace is rapidly cooled to form a scale with many cracks, thereby facilitating the permeation of the acid solution and improving the descaling property. Further, by promoting the oxidation of the surface of the object to be treated, the magnetite layer occupies the majority, and a scale with a thin wustite layer is formed at the base iron interface. And, many cracks are generated in this scale by rapid cooling of 8 ° C./minute or more. For this reason, the dense and thick magnetite layer easily holds the thin wustite layer and peels it off, and facilitates descaling by a mechanical method. Further, the acceleration of the oxidation of the surface of the article to be treated is performed at a temperature of 560 ° C or higher.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the whole of this continuous heat treatment apparatus, 1 is a continuous atmosphere furnace whose inside is kept in a reducing atmosphere, 2 is a heater provided in the continuous atmosphere furnace 1, 3 is a ceiling fan,
4 is a wire coil which is a treated product, and 5 is a hearth roller provided in series in the furnace. 6 is a purge chamber provided at the inlet of the continuous atmosphere furnace 1, 7 is a door chamber provided between the purge chamber 6 and the continuous atmosphere furnace 1, and 8 is provided outside the continuous atmosphere furnace 1. It is the entrance table.

The treated product 4 is carried into the purge chamber 6 from above the inlet table 8, the air in the purge chamber 6 is replaced with atmospheric gas, and then the treated product 4 is loaded into the continuous atmosphere furnace 1. . The processed product 4 loaded in the continuous atmosphere furnace 1 is a roller 5
Thus, while being conveyed in the direction of the arrow in the furnace, it is heated and soaked to a predetermined temperature by the heater 2 and taken out to the oxidation chamber 9 at about 650 ° C. 10 is a door chamber provided between the oxidation chamber 9 and the outlet of the continuous atmosphere furnace 1. Oxidation chamber 9
The processed product 4 taken out of the continuous atmosphere furnace 1 is 700 to
A heat-retaining heater 11 is provided so that the temperature can be maintained at 560 ° C. A blower 12 is provided so that air can be introduced into the oxidation chamber 9 from the outside. Although not shown, the oxidizing chamber 9 is provided with a purge gas supply port so as to function also as a purge chamber.

A cooling chamber 13 is provided for rapid cooling of the processed product 4 taken out of the oxidation chamber 9.
As shown in FIG. 2, by providing fans 14, 15 and 16 for blowing the outside air to the hearth and both side walls, respectively, and applying an air blast of the outside air to the lower surface and surroundings of the wire rod coil 4 in the cooling chamber 13. The wire coil 4 can be rapidly cooled at a rate of 8 ° C./minute or more, preferably 10 ° C./minute or more. 17
Indicates an exhaust port provided on the ceiling of the cooling chamber 13. 1
Reference numeral 9 denotes a transfer carriage provided outside the cooling chamber 13.

In this heat treatment apparatus, the treated product 4 charged in the oxidation chamber 9 is kept at a temperature near the surface thereof at a temperature of 700 ° C. or less at which oxidative decarburization does not occur and at a temperature of 560 ° C. or more at which magnetite does not precipitate at the base iron interface. It is oxidized by introducing air. Here, the temperature near the surface is the temperature of the portion including the scale on the surface of the processed product. The temperature at which oxidative decarburization does not occur and magnetite does not precipitate on the surface of the base metal varies depending on the steel type, but it is preferable that the temperature range is 700 to 560 ° C in consideration of safety.

This oxidation is also carried out to re-oxidize a part of the secondary scale reduced in the atmospheric furnace and to burn the carbon adhering in the sooting in the furnace. It is performed to generate a wustite layer.

A large number of cracks are generated in the scale of the processed product 4 by transferring the processed product 4 in which the scale has been generated in the oxidation chamber 9 to the cooling chamber 13 and applying a blast to its surface to rapidly cool it. This quenching is performed so as to quench at least the temperature range from the formation start temperature of magnetite at the base metal interface to the transformation end temperature of the wustite formed at the base metal interface (at least in the range of 560 ° C to 350 ° C depending on the steel type). When this temperature range is gradually cooled, the wustite at the base metal interface is transformed into magnetite and the descaling property deteriorates significantly.

The cooling rate is 8 ° C./min or more, preferably 10 ° C./min or more, though it depends on the steel type. For this purpose, a fan is provided in the cooling chamber 13 so as to surround the article to be treated 4 from both sides and from below, and it is possible to achieve such a cooling rate by directly blowing the wind against the surface. The cooling atmosphere is not particularly limited and may be air, N ₂ , or a reducing atmosphere. As the cooling means, other cooling means, for example, spraying of spray water, immersion in a cooling water tank, or the like may be adopted.

In this way, the treated product in which many cracks are contained in the scale due to the rapid cooling can be cleaned easily by a mechanical descaling means such as shot blasting, roll bending, air blasting, or pickling so that the surface can be easily cleaned. Can be significantly increased.

An independent purge chamber may be provided between the continuous atmosphere furnace 1 and the oxidation chamber 9. In that case, the oxidation chamber 9 and the cooling chamber 13 may be integrated into one chamber, and the oxidation and the cooling may be performed in the same chamber.

Further, the above-mentioned embodiment is an example of a heat treatment furnace provided with an oxidation chamber, but it is not always necessary to oxidize the treated product which has been subjected to a pickling treatment before the heat treatment, and the oxidation chamber is omitted. However, the descaling property is improved.

Furthermore, if the cooling in the cooling chamber is carried out by introducing an oxidizing gas, the descaling property can be improved without the oxidizing chamber.

Further, the continuous atmosphere furnace and the cooling chamber are connected to each other through a conveying means in the atmosphere such as a roller conveyor,
If the surface of the article to be treated is oxidized while the article to be treated is conveyed to the cooling chamber, the descaling property is improved even if the oxidizing chamber is eliminated.

[0020]

As described above, according to the present invention, the descaling property of the treated product is remarkably improved, and the scale can be more completely removed by pickling or mechanical method, and there is a beneficial effect of improving the quality.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the entire continuous heat treatment apparatus for improving the descaling property according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a cooling chamber.

[Explanation of symbols]

 1 Continuous Atmosphere Furnace 2 Heater 4 Processed Product 9 Oxidizing Chamber 11 Heat Keeping Heater 12 Blower 13 Cooling Chamber 14, 15, 16 Fan

Claims (6)

[Claims] 1. A continuous atmosphere furnace in which treated products such as wire rods are continuously conveyed into a furnace kept in a reducing atmosphere and heated, soaked and subjected to a predetermined heat treatment, and a continuous atmosphere furnace taken out from the continuous atmosphere furnace. A continuous heat treatment apparatus for improving descaling properties, which comprises a means for oxidizing the surface of a treated product and a cooling chamber for rapidly cooling the treated product whose surface is oxidized. 2. A continuous atmosphere furnace in which treated products such as wire rods are continuously conveyed into a furnace kept in a reducing atmosphere to heat, soak and perform a predetermined heat treatment, and a continuous atmosphere furnace taken out of the continuous atmosphere furnace. Improving descaling characteristics, which is characterized by comprising an oxidation chamber in which a treated product is charged and an oxidizing gas is introduced into the chamber, and a cooling chamber for rapidly cooling the treated product taken out from the oxidizing chamber. Continuous heat treatment equipment. 3. A continuous atmosphere furnace in which treated products such as wire rods are continuously transferred into a furnace kept in a reducing atmosphere to heat, soak and perform a predetermined heat treatment, and a continuous atmosphere furnace which is taken out from the continuous atmosphere furnace. A continuous heat treatment apparatus for improving descaling property, comprising a cooling chamber for rapidly cooling a processed product, wherein the continuous atmosphere furnace and the cooling chamber are connected by a transfer means. 4. A continuous atmosphere furnace in which treated products such as wire rods are continuously conveyed into a furnace kept in a reducing atmosphere and heated, soaked and subjected to a predetermined heat treatment, and a continuous atmosphere furnace taken out from the continuous atmosphere furnace. A continuous heat treatment apparatus for improving descaling properties, which comprises a cooling chamber for rapidly cooling a processed product, and an oxidizing gas is introduced into the cooling chamber. 5. The temperature of the processed product in the oxidation chamber is 700 to 560.
The continuous heat treatment apparatus for improving the descaling property according to claim 2, wherein the temperature is kept at 0 ° C and air is introduced. 6. At least 56 processed products in the cooling chamber.
The continuous heat treatment apparatus for improving the descaling property according to any one of claims 1 to 4, wherein the range of 0 ° C to 350 ° C is cooled at a cooling rate of 8 ° C / min or more.