JPS6227127B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a direct processing heat treatment equipment array for hot-rolled wire rods, and in particular, to heat-treating hot-rolled wire rods, such as drawing materials, during the manufacturing process of the hot-rolled wire rods. The aim is to advantageously provide suitable wire drawability and other properties depending on the application.

Conventionally, in the production of piano wire, spring steel wire, etc., in order to give properties suitable for drawing processing to the hot-rolled wire rod (including bar-in coils; the same applies hereinafter), which is the raw material, prior to such processing, patenting and Softening heat treatment was required. However, such reheat treatment not only requires a large amount of thermal energy for heating, but also has disadvantages in terms of energy and resource conservation because scale loss is inevitable. It was strongly desired.

In order to meet the above requirements, a direct heat treatment method has been developed that utilizes the high heat of the wire immediately after hot finish rolling to control the cooling rate of the wire to improve the material quality. With this, it has become possible to obtain a wire rod with drawability comparable to that of a wire rod that has been subjected to a patenting treatment as a pretreatment for drawing.

FIG. 1 shows a conventional direct heat treatment equipment array used for this direct heat treatment.

In this equipment row, the wire rod finished into a predetermined size and shape by a finishing mill 1 is then processed by a cooling device 2.
The material is cooled with water, then wound into a loop or coil by a winder 3, and appropriately cooled by a regulating cooling device 4. Note that the number 6 in the figure represents the pass line of the material to be rolled.

By the way, in recent years, in order to further improve the material properties of metal materials, especially to make them tougher, mechanical heat treatment such as ausforming, which is a combination of plastic working method and heat treatment method, is a heat treatment that causes plastic deformation to supercooled austenite during quenching and cooling. With the development of controlled rolling methods in which rolling is carried out under temperature control and temperature control, it has become possible to obtain both high toughness and strength.

Therefore, if heat treatment such as ausforming and controlled rolling described above can be applied to the wire manufacturing process, great effects can be expected in improving the material quality, but conventional equipment as shown in Figure 1 In columns, this application was impossible.

In other words, in the equipment row shown in Fig. 1, the intervals between the stands of the finish rolling mill 1 are generally short, and rolling is performed at high speed and high area reduction, so the temperature of the material to be rolled rises and Therefore, rolling in the supercooled austenite region of about 500°C cannot be performed as it is. In order to lower the processing temperature, it is possible to slow down the rolling speed or lower the temperature at which the rolled material is extracted from the heating furnace, but either method will lead to a decrease in productivity, and if the processing temperature is lowered, Since the deformation resistance of the material to be rolled increases and the rolling load increases, the capacity of the rolling mill must be increased accordingly, adding to the disadvantage that equipment investment costs increase. Moreover, even if the above-mentioned low-temperature processing was carried out, the quality of the resulting material would not be significantly improved compared to the reheat-treated material.

This invention advantageously solves the above-mentioned problems, and allows direct implementation of ausforming, controlled rolling, etc. in the wire manufacturing process, as well as introducing processing strain into the wire and actively utilizing this processing strain. We propose a direct processing heat treatment equipment array that can also perform softening treatment.

That is, the present invention includes a first rolling mill that partially hot-finish-rolls a long steel product that has undergone rough rolling and intermediate rolling, and a first rolling mill that partially hot-finish-rolls a long steel product that has undergone rough rolling and intermediate rolling;
A cooling device that rapidly cools down to a temperature above the Ms point at a cooling rate that maintains at least the majority of the structure as supercooled austenite, and a cooling device that applies plastic working to this coolant to introduce processing strain and form it into a predetermined size and shape. This is a direct processing heat treatment equipment array for hot rolled wire rods, which is arranged in order of a second rolling mill for finishing, a winding machine for bundling the rolled wire into coils, and a heat treatment equipment for the wound material.

In this invention, by arranging the rolling mill before and after the cooling device, it is possible to control the rolling temperature and rolling reduction over a wide range, and this is the first time for online control such as ausforming and controlled rolling in the wire manufacturing process. Implementation has been achieved.

This invention will be specifically explained below with reference to the embodiment shown in FIG.

In Fig. 2, 1' is a first rolling mill, 2' is a cooling device, 3 is a winding machine, 4' is a heat treatment device, and 5 is a winding machine.
is the second rolling mill. Note that 6 is a pass line of the material to be rolled.

The first rolling mill 1' partially hot-rolls the long steel material that has undergone rough rolling and intermediate rolling into a semi-finished wire product, and the amount of reduction is the amount of reduction applied by the second rolling mill 5 in the subsequent process. Accordingly, a half-finished wire rod is obtained in the first rolling mill 1', and after cooling, the remaining rolling amount is processed in the second rolling mill 5 to finish rolling the wire rod to the dimensions.

The cooling device 2' is equipped with a cooling means such as a spray pipe so that the half-finished wire rod after hot rolling can be uniformly and rapidly cooled, and is equipped with a cooling means such as a spray pipe, which can cool the wire rod half-finished product after hot rolling. It enables rapid cooling to any temperature corresponding to the desired characteristics.

In addition, in the second rolling mill 5, processing strain is introduced into the coolant cooled to a predetermined temperature by the cooling device 2', and the material is finished into a predetermined size and shape. The number of stands used and the amount of reduction are limited depending on the purpose so as not to exceed.

The winding machine 3 bundles the rolled material having a predetermined size rolled in the previous process to facilitate subsequent processing, and an existing winding machine can be used.

The heat treatment device 4' is equipped with a rapid cooling device using blast air, hot water, etc., a slow cooling device, a heat retention device, a heating device, and a quenching and tempering device, which are appropriately selected and used depending on the required material of the wire. .

Next, a case will be described in which direct heat treatment is actually performed using the above-mentioned equipment array.

Now, the steel pieces extracted from the heating furnace reach the first rolling mill 1' after passing through a rough rolling mill and an intermediate rolling mill. Here, partial hot rolling is performed in consideration of the rolling reduction amount in the second rolling mill in the subsequent process. This hot-rolled material is then cooled to a temperature above the Ms point at a cooling rate that maintains at least the majority of the structure as supercooled austenite, and to a temperature suitable for imparting properties depending on the product's intended use, and then subjected to a second process. 2. The coolant is subjected to plastic working using a rolling mill 5 to finish the coolant into a predetermined wire rod size and shape. The rolled material subjected to processing strain by the second rolling mill 5 is immediately bundled into a coil shape by the winder 3 and promptly conveyed to the heat treatment device 4. And heat treatment equipment 4'
Then, appropriate heat treatment is selected from among rapid cooling, slow cooling, self-tempering, heat retention, heating, quenching/tempering, etc., depending on the material required for the wire product.

As mentioned above, in the direct pressure heat treatment equipment array according to the present invention, the rolling temperature and rolling reduction settings can be changed over a wider range than in the conventional example, and as a result, the wire rod passing at high speed is subjected to controlled rolling and orthoforming. It is now possible to perform various treatments online depending on the use of the wire, such as mulching and softening treatment.

Hereinafter, a case in which typical processing heat treatment is performed by applying the present invention will be described.

First, when performing controlled rolling, the wire rod half-finished product immediately after hot rolling is rapidly cooled to an arbitrary temperature up to the γ + α two-phase mixing region in the cooling device 2', and then the second rolling mill 5
After rolling, the wire rod may be appropriately cooled in a heat treatment device 4', and thus a wire rod with high strength and high toughness can be obtained.

Next, ausforming is performed by cooling the semi-finished wire rod immediately after hot rolling in the cooling device 2' at a cooling rate that maintains at least the majority of the structure into supercooled austenite, and at a temperature above the Ms point and up to about 500℃. Rapidly cool to temperature and immediately reduce to supercooled austenite with a reduction rate of 20%
After being finish-rolled to a certain degree or higher, it is wound up and then rapidly cooled in a heat treatment device 4'. In addition, as a modification of ausforming, a semi-finished wire product is rapidly cooled to about 700℃, then rolled at a reduction rate of 20% or more, and then quenched and tempered in a heat treatment equipment 4'.In either case, high strength is achieved. , high toughness wire rod can be obtained.

In addition, when softening treatment is performed using processing strain, the rolled wire with the processing strain introduced in the second rolling mill 5 is subjected to slow cooling, self-tempering, heat retention, or heating in the heat treatment device 4'. Although this process requires heating, the amount of heat energy required is far less than that required for reheating at the processing manufacturer.

Thus, according to the present invention, it is possible to easily perform ausforming, controlled rolling, and softening treatment in the wire manufacturing process, and therefore, it is possible to easily perform ausforming, controlled rolling, and softening treatment in the wire manufacturing process, and therefore, it is possible to easily perform ausforming, controlled rolling, and softening treatment in the wire rod manufacturing process. Various materials depending on the application, ranging from high-strength/high-toughness wire rods to soft wire rods, can be appropriately applied online.

Further, according to the present invention, pretreatment prior to cold working such as drawing, cutting, and cold forging can be omitted, which greatly contributes to labor and energy saving.

[Brief explanation of the drawing]

FIG. 1 is an array diagram showing a conventional direct heat treatment equipment array used for direct heat treatment, and FIG. 2 is an array diagram showing a direct processing heat treatment equipment array according to the present invention. 1'...First rolling mill, 2'...Cooling device, 3...
Winding machine, 4'... Heat treatment device, 5... Second rolling mill.

Claims (1)

[Claims] 1. A first rolling mill that partially hot-finish-rolls a long steel bar that has undergone rough rolling and intermediate rolling, and a first rolling mill that partially hot-finish-rolls a long steel bar that has undergone rough rolling and intermediate rolling. a cooling device that rapidly cools the cold austenite at a cooling rate maintained;
A sequential arrangement of a second rolling mill that applies plastic working to the coolant and finishes it into a predetermined size and shape while introducing processing strain, a winding machine that bundles the rolled wire into a coil, and a heat treatment device for the rolled material. A row of heat treatment equipment for direct processing of hot rolled wire rods.