JPS5927641B2 - Manufacturing method and equipment for small diameter wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for manufacturing a small diameter wire, particularly a wire rod having a diameter of 5.5 mm or less.

Conventionally, wire rods are produced by rolling ingots, which are obtained by continuously casting steel ingots or molten steel, in a blooming process to obtain billets, or by sending them to a wire rod rolling process without going through the blooming process. Billets, steel ingots, or slabs were rolled to a minimum diameter of 5.5 nutφ using several continuous hot rolling mills.

The thus obtained wire rod is processed into a wire having a diameter of 5.5 mm or less by cold wire drawing or cold rolling using the kneaded wire as a wire.

In the thin wire manufacturing process in the conventional process as described above, if the thin wire manufacturing process is viewed as a simple wire thinning process, the following problems arise.

(1) Since it is cold working, more energy is required for area reduction than in hot working.

(11) Depending on the wire material, there is a processing limit in cold working, so it is necessary to perform softening annealing (patenting) during the cold working process.

This heat treatment process such as intermediate annealing is not necessary in view of the material properties required for the final product.

In order to solve these problems, if we try to obtain wires with a diameter of less than 5.5 mmφ by hot rolling, for example, it is necessary to heat rolls in small loft units for each product size required by secondary wire processing manufacturers. Since inter-rolling must be performed, conventional rolling methods are forced to significantly reduce production efficiency.

In hot rolling of wire rods, the product of the rolling material cross-sectional area and the speed becomes maximum when the wire diameter is around 7 mmφ or 9 m in conventional thin wire mills that mainly manufacture wire rods of 5.5 mmφ.
Since the wire diameter is around mφ, hot rolling with this wire diameter is most preferable in terms of rolling efficiency.

Therefore, if wire diameters of 5.5 mm or less are hot-rolled in small loft units, productivity will decrease due to both a decrease in rolling efficiency and a decrease in equipment operation rate due to changes in rolls, etc. This causes high costs.

Conventionally, in order to satisfy these two conflicting demands to a certain extent, hot rolling has been carried out to a wire diameter of 5.5 mm.

The decrease in productivity in hot rolling can be improved to some extent by increasing the rolling speed, but there are equipment limitations to increasing the rolling speed, and as the wire diameter becomes smaller, the cross-sectional rigidity of the material decreases. Since this decreases in proportion to the square of the wire diameter, it causes operational problems such as misrolling due to so-called buckling during rolling, so not much can be expected.

In any case, the production efficiency (output per unit time) S is expressed as SOCd''-y (d: wire diameter, V: speed), and the effect of wire diameter on raw mahjong efficiency is the effect of speed. far exceeds.

Therefore, when obtaining wire rods by hot rolling, it is not a good idea to roll wire rods with a small loft and a diameter of less than 5.5 mm using hot rolling equipment that requires a large amount of equipment cost.

The present invention was made to solve the above-mentioned problems in conventional wire rod hot rolling.

The present invention uses wire rods obtained through conventional rolling processes such as rough rolling, intermediate rolling, and finishing rolling as an intermediate product, and after cooling to a temperature that suppresses the formation of secondary scale, After being charged into heat retention or heating furnaces arranged in rows and heat retention or heating, the thin wire is rolled using a special rolling machine.
It is characterized by the fact that the heat treatment is carried out without heating after thin wire rolling is performed with heat generated during processing to reach the heat treatment start temperature.

The present invention will be explained in detail below.

In the process according to the present invention, a thin wire material is first obtained through the conventionally known processes of heating, rough rolling, intermediate rolling and finish rolling.

The intermediate product after finish rolling is cooled, for example, in a cleaning trough at a temperature range of 600 to 700°C or at 850°C.
A scale generation preventive agent such as glass powder or biocalcium phosphate is applied at a temperature range of ~900°C to suppress the generation of secondary scale as much as possible.

Although such processing may be carried out in a conventional process line including the above-mentioned intermediate rolling and finish rolling, it may be carried out in the entry section of a thin wire dedicated rolling line provided as a sub-column to a conventional rolling line, which will be described later. You can also do it with

The wire rod, which has been treated to suppress the generation of secondary scale, is placed in a heat retention furnace and is retained or heated to 600 to 700°C.

The intermediate product taken out from the heat retention furnace is rolled into a thin wire using a rolling mill dedicated to thin wire.

Due to heat generation during this rolling process, the material dimensions, intermediate product temperature (temperature when extracted from the heat retention furnace), and each pass in the thin wire rolling mill are adjusted so that the wire rod temperature after rolling matches the heat treatment start temperature. One or more conditions such as stretching □ are changed.

The plant material processed into fine wires in this way is then subjected to online heat treatment to become a product.

An example of such a procedure for setting rolling conditions is shown in FIG. 3.

Material cross-sectional diameter dn, material speed V at the entrance of a rolling mill dedicated to fine wire, and material temperature T.

, the stretching λ1 of each pass in a rolling mill dedicated to thin wire. λ2...
・,λ1...λ.

is given, and the amount of temperature increase 2n due to processing heat in the rolling mill exclusively for thin wire is calculated.

Furthermore, we calculated the amount of temperature drop due to cooling during the rolling process,
Diameter d and temperature T of the wire in the final finished state.

seek. If dn and Tn match the wire diameter required for the rolled product and the heat treatment start temperature, then rolling is performed under those conditions to start heat treatment.

If they do not match, the calculation is performed again by changing the parameters in the initial conditions that can be operated for each pass extension, etc.

Thus, rolling is performed under conditions that satisfy dn and Tn.

It is of course possible to obtain a wire rod having a diameter of 5.5 mm or more using the conventionally known process for obtaining the intermediate product described above.

The present invention will be specifically explained below.

1 in FIG. 1 schematically shows a conventional wire rod rolling process.

That is, a billet with a width of 80 to 120 widths is heated to a predetermined temperature in a heating furnace 1, and then passed through a rough rolling mill 2, an intermediate rolling mill 3,
After passing through a finish rolling mill 4, various cooling devices (not shown), and a cooling trough 5, it enters an adjustment cooling device 6 after finish rolling, where it is wound up by a winding machine 7, and then sent to a refining process.

The thin wire exclusive rolling line [F] of the present invention branches off to another line [F] from the middle of the above-mentioned wire rod rolling process (2).

At this time, the wire rod is wound once, but immediately after exiting the rolling process (①), it is cooled in equipment such as the cooling trough of the (① line) or the (③ line), and is then wound.

In addition, at any point between the end of rolling and the time of winding,
In other words, if a secondary scale prevention agent such as glass powder or biocalcium phosphate is applied before or after the cooling trough, secondary scale will be removed during transport, heat retention, and uncoiling until the subsequent secondary rolling process. It is possible to suppress the occurrence of this to an extremely small amount, and it is possible to achieve an extremely good surface texture of the product after fine line finishing.

Note that depending on the components of the secondary scale inhibitor, it is determined whether it is applied before or after the cooling trough.

For example, in the case of glass powder, it is preferable to apply the coating at a temperature of about 850 to 900°C.

The wound coil passes through a predetermined path, is protected at a predetermined temperature in a low-temperature heat retention furnace, and is sequentially led to an uncoiler.

In the uncoiler, the coil is similarly kept at a predetermined temperature until the uncoiling is completed.

For example, in the case of a 2 ton coil with a diameter of 12 mm, as shown in Table 1, it will take about 30 minutes to complete the uncoiling of one coil, that is, until the rolling is finished. Heat retention is required during this time as well.

Note that it is also possible to join both ends of each coil to the respective ends of the preceding and following coils by, for example, flash butt welding, and perform endless rolling, thereby further improving the rolling efficiency.

Heat retention temperature from transfer to heat retention furnace and uncoiler is 6.
00-700°C is preferred.

The reasons for this are the occurrence of secondary scale during the strand stage, that is, during transportation, heat retention, etc., prevention of decarburization, deformation resistance and hot brittleness of the material during rolling, ie deformability, and in-line heat treatment at the completion of thin wire rolling. The most preferable temperature range is 600 to 7 in terms of sufficient finishing temperature etc.
00℃ teal.

Figure 2 schematically shows the temperature transition of the material according to the process from the time of billet extraction. 1 is the cooling process in the cooling trough, 2 is the transfer process from coil winding to the heat retention furnace, and 3
is the temperature during heat retention, and 4 is the temperature during rolling.

The rise in material temperature in No. 4 is due to processing heat generation, and the key point of the present invention is to effectively utilize this processing heat generation to perform in-line heat treatment, so that thermal energy is utilized extremely efficiently.

The heating heat generation is closely related to the average area reduction rate of each hole type during the rolling process, the stand distance, the rolling speed, and the material of the rolled material.

For example, for high carbon steel wire rods such as 5WRH62A, Table 2
By keeping the heat retention temperature at 600℃ as shown in
By setting the rolling speed to 1.25 Ml5 at the entrance of the AI path, it was possible to secure a temperature of 1000°C at the time of 3φ finishing, and the subsequent in-line heat treatment could be performed under extremely good conditions.

Next, the rolling mill and subsequent parts will be explained in detail.

The rolling mill is a continuous rolling mill of the type usually called a block mill, which has an H to V arrangement in which rolling is applied alternately from the longitudinal and lateral directions, or an X-shaped arrangement in which the horizontal axis of the rolls is tilted alternately by ±45°. G) is preferred.

At this time, since the wire rod has a small diameter, using the conventional mill as it is increases the frequency of troubles such as misrolling, so it is preferable to set the following conditions.

In other words, based on the example of 12φ→3φ, a) use small diameter rolls (D=100 to 150φ) as much as possible, and b) keep the distance between adjacent roll pairs as close as possible (t
= 300 to 500 degrees), 2) Active tension (σ) is applied between adjacent stands during rolling.
By adding t/k = 0.01 to 0.30 (yield stress), etc., stable rolling is performed, and at the same time, elongation efficiency is increased, making the entire rolling mill extremely compact and reducing equipment costs. can save significantly.

The rolling speed is around 1.25M/S at the entrance of the block mill.
By setting the final rolling speed to around 20 M/S (in the case of 3φ), the temperature of the material at the end of rolling can be raised to 950° C. to 1000° C. by processing heat, which is sufficient to carry out the subsequent in-line heat treatment.

For example, for 5.5φ or more, it is easier to control the cooling rate by performing isothermal transformation heat treatment, or direct patenting treatment, which is normally used for high C hard steel wire rods, with 3φ, and the temperature difference at the center of the surface layer is extremely small. Since it can be made small, it is possible to approach the ideal cooling curve in an extremely uniform state over the entire cross section, and naturally a high standard of wire quality can be obtained.

Note that the joints joined at the entrance side of the heat retention furnace are automatically detected and marked after rolling, and can be cut and removed at an appropriate stage.

The rolling speed of 20 to 30 M/S is not only sufficient to obtain a finishing temperature sufficient for in-line heat treatment of wire rods made of various materials, but also to detect the aforementioned joints, dimensions, and defects. This speed is extremely advantageous in terms of ease of detection, in-line cutting, and in-line heat treatment.

For example, instead of the conventional Stelmore adjustment cooling method used for 5.5φ or more, it enables isothermal transformation heat treatment during the linear transfer process after finish rolling. It is possible to avoid variations in material quality caused by overlapping parts of wire rods, transport conveyors and wire rods, etc., and it is possible to obtain good products.

As described above, the present invention improves production efficiency and makes effective use of thermal energy in both the primary rolling from a billet to a wire rod and the secondary rolling from a large wire rod to a thin wire rod. The present invention provides an extremely excellent wire rod rolling method and layout that can eliminate drawbacks such as scale loss and freely obtain high-level and low-level carbon steel wire rods.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the relationship between the conventional rolling method and the present invention, and each process of the present invention, Fig. 2 is a diagram showing a schematic material temperature transition in the primary rolling and secondary rolling, and Fig. 3 The figure is a diagram showing an example of a method for setting a rolling method. Fig. 1, 1: heating furnace, 2: rough rolling mill, 3: intermediate rolling mill,
4: Finish rolling mill, 5: Cooling trough, 6: Adjustment cooling device, 7: Winding machine, Fig. 3, QIW: Plastic working calorific value, Qlp: Plastic working frictional calorific value, Q2 R: Cooling device by radiation, Q2CV1 : Cooling heat amount due to air convection,
Q2CV2: Cooling heat amount due to water convection, Q2 Cooling water amount due to heat conduction caused by contact with CD' roll, C: Specific heat,
γ: specific weight, a: thermal conductivity, 12 hours, temperature with two T lines,
d: Wire size.

Claims (1)

[Scope of Claims] 1 A steel billet is subjected to primary rolling including rough rolling, intermediate rolling, and finish rolling to obtain a wire rod of a predetermined wire diameter, and after cooling the wire rod to a temperature at which generation of secondary scale is suppressed, The material is charged into heat retention or heating furnaces arranged in sub-rows, heat-retained or heated, and then subjected to second rolling to raise the temperature, and then heat treatment is started without heating. A method for manufacturing small diameter wire rods. 2. A heat retention furnace for retaining or heating the wire rod coil, a secondary rolling mill, and an online heat treatment device are installed as sub-columns to the primary rolling machine consisting of a rough rolling mill, an intermediate rolling mill, and a finishing rolling mill. A line of manufacturing equipment for small diameter wire rods.