JPH067827A - Side looper roller for rolling hot wire rod - Google Patents

Abstract

PURPOSE:To improve resistance of the side looper roller used for forming a loop when the metallic wire rod is subjected to hot rolling. CONSTITUTION:A sintered body containing 93-99.5weight% silicon nitride or sialon is formed into a roll shape. This side looper roller 1 for rolling the hot rolled wire rod has high resistance for a thermal shock and a mechanical shock generated by contact with the hot wire rod 2, especially, is excellent in wear resistance, can maintain the side looper property stably extending for a long period of time without deteriorating the quality of the wire rod and also, contributes to improvement of productivity of the wire rod.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a side looper roller used for guiding a metal wire rod in a side looper in a process of hot rolling a metal wire rod such as iron.

[0002]

2. Description of the Related Art Conventionally, a metal wire rod, particularly a steel wire rod, is produced by a multi-stage rolling system in which a rough rolling mill, an intermediate rolling mill, and a finishing rolling mill are continuously passed.

Between these rolling mills, a side looper for forming an arc-shaped loop on the wire rod is installed for rolling the wire rod continuously without tension.

This side looper is provided with a side looper roller which serves as a fulcrum for making a loop on the wire.

Carbon steel was initially used for this side looper roller, but the use of rolls having higher hardness has been aimed at, and in recent years, cemented carbide rolls such as CrMo steel have come to be used ( Reference technology JP-A-62-577
07).

[0006]

The temperature of the wire which comes into contact with the side looper roller made of this cemented carbide is 900.
At ~ 1100 ° C, the running speed of this wire is 5 ~ 100
Due to the severe m / s, the surface of the side looper roller often wears after a short period of use.

When the side looper roller is worn, it must be replaced, and the wire rod and the rolling line must be stopped, which is the biggest factor in the decrease in the wire rod productivity.

The following causes are considered to be the causes of the above wear in the side looper roller made of cemented carbide.

Cemented carbide is a material that is excellent in strength and hardness at room temperature, but its physical properties are significantly deteriorated at high temperatures. Therefore, wear resistance as expected when used for cold working rolls and dies. I can't get sex. Further, cemented carbide is a material that has poor resistance to oxidation at high temperatures.

For this reason, oxides that easily fall off are produced on the surface that comes into contact with the hot wire during rolling. In addition, this cemented carbide has a large specific gravity (large inertia), a large rotational resistance, and a large friction with the wire, so that the wear progresses rapidly.

When the cemented carbide side looper roller is worn in this manner, the surface of the roller is markedly roughened, which is a direct cause of deterioration of the surface quality of the wire.

In the case of the cemented carbide side looper roller, Co, which is one of the constituents of the side looper roller, easily reacts with the scale on the surface of the wire, and scale sticking easily occurs on the surface of the roller. This seizure will significantly impair the surface quality of the wire.

The present invention has been made to solve the above-mentioned problems, and provides a side looper roller for hot wire rod rolling which does not have the problems such as the side looper roller made of conventional cemented carbide or carbon steel. It is provided.

[0014]

The present invention relates to a side looper roller for rolling hot wire, which is formed into a roll shape from a sintered body containing 93 to 99.5% of silicon nitride or sialon. It has excellent resistance to thermal shock and mechanical shock, has little surface deterioration, and can maintain a stable side looper roller function for a long period of time, enabling high-quality wire production with high productivity. It is a thing.

The present invention will be described in detail below.

The inventors of the present invention first sought ceramics highly suitable for a side looper roller for wire rod rolling, which has poor reactivity with scale at high temperatures and does not cause significant strength and hardness deterioration at high temperatures like cemented carbide. Was examined.

As a result, among the ceramics, ZrO ₂
Zirconia-based sintered ceramics containing Al as a main component, Al₂
O₃Alumina-based sintered ceramics containing Si as a main component, Si
Each of the silicon carbide based ceramics containing C as the main component
The thermal shock resistance temperature is about 550 ° C. or less.

The thermal shock resistance temperature of silicon nitride and sialon-based sintered ceramics is 650 ° C. to 1000 ° C., which is superior to the above ceramics in thermal shock resistance.

The side looper roller for rolling the wire rod is
There is a large temperature difference between when the wire rod contacts the high temperature wire and when it does not contact the wire rod, and it is used under the condition that a large thermal shock is repeatedly applied in the rotating state.

For this reason, the side looper roller formed of zirconia-based sintered ceramics, alumina-based sintered ceramics, silicon carbide-based sintered ceramics, etc., which have poor thermal shock resistance, is susceptible to cracking and cracking and cannot be used. .

On the other hand, in the side looper roller formed of sintered ceramics such as silicon nitride and sialon, cracks and cracks due to thermal shock are unlikely to occur.

Further, the side looper roller formed of silicon nitride, sialon or the like has a dense silica glass oxide layer having a strong bonding force formed on the surface thereof by the action of cooling water and heating, and this is in contact with the wire to give a mirror surface. Therefore, the progress of oxidative wear is further prevented, the surface of the wire is not roughened, and the surface quality of the wire is not deteriorated.

Further, since it is considerably lighter than the cemented carbide roller and easily rotates when the wire is in contact (small inertia), friction with the wire can be reduced and wear of the roller and the wire can be reduced.

From the above, it was confirmed that silicon nitride and sialon are highly suitable materials for the side looper roller.

When the thermal shock greatly acts due to the difference in the life of these materials and the cemented carbide, it becomes more remarkable at higher temperatures, and under the operating conditions such as the side looper for wire rod rolling, silicon nitride and sialon are more preferable. It was concluded that it has a long life and is cost effective.

Therefore, it is essential that the side looper roller of the present invention is formed of a sintered body containing silicon nitride or sialon as a main component.

As the sintering aid containing silicon nitride as a main component, for example, magnesia, yttria, beryllia,
Alumina, aluminum nitride, silica and the like are preferable, but as a sintering aid containing Sialon as a main component,
For example, aluminum nitride and yttria are suitable.

When the above-mentioned various sintering aids or other ceramics are contained in an amount exceeding 7% by weight, the hardness of the sintered body is reduced and the abrasion resistance of the side looper roller is reduced.

Therefore, it is desirable that the content of components other than silicon nitride and sialon is as low as possible, and it is desirable to keep the content to the minimum necessary when it must be contained as a sintering aid.

It is desirable that the silicon nitride and sialon sintered body have a density of 96% or more, and particularly preferably 97% or more of the theoretical density.

The density of the sintered body is a very important condition,
If this is not satisfied, it is vulnerable to mechanical shock and its life becomes short.

In order to increase the density of the sintered body to a theoretical density of 96% or more, the particle size of the raw material powder, particularly the silicon nitride as the main component, the particle size of the sintering aid, and the method of manufacturing the sintered body are extremely important. Becomes important.

The particle size of the raw material powder is preferably as small as possible, and specifically, the size in the range of 0.2 to 50 μm is desirable. Particularly desirable is 10 μm or less.

If the raw material powder is less than 0.2 μm, it tends to scatter in the atmosphere when the powder is mixed, and the powder becomes difficult to handle.

If the particle size of the powder is larger than 50 μm, it is difficult to increase the density and a high pressure is required to produce a sintered body.

Furthermore, the mechanical impact resistance of the produced sintered body is significantly lower than that when a sintered body having a grain size smaller than that is used.

In order to produce a sintered body having a density of 96% or more of the theoretical density, it is desirable to adopt a method by pressure sintering.

As the pressure sintering method, it is desirable to apply, for example, a hot pressing method or a hot isostatic pressing (HIP) method.

Further, the rollers produced by the hot pressing method and the HIP method have abrasion resistance and mechanical resistance by leaving the surface dense layer formed during firing by minimizing the cutting allowance for grinding to the final shape after sintering. The impact resistance can be made higher.

In the case of rolling a wire rod, when the tail of the wire rod passes through the side looper, it swings laterally and hits the side looper roller, so that a mechanical impact is also applied to the side looper roller.

The side looper roller containing silicon nitride or sialon as a main component of the present invention has a solid roller shape as shown in FIG. 3 and has a shaft portion at both ends, or a sleeve as shown in FIG. Roller-shaped hollow part 4
A shaft 3 is fitted and attached to both ends of the sleeve roller. In this case, a heterogeneous ceramic may be provided as a core material (filler) in the hollow portion 4 of the sleeve roller or the shaft 3 may be extended ( It may be used as a core material after being penetrated.

Although there are various methods of forming the side looper roller, it is necessary to consider the diameter and thickness of the side looper roller in order to secure sufficient resistance to the mechanical impact.

First, although the diameter is not related to the wire diameter, the outer diameter D of the normal size (3 to 20 mm) is 5 cm or more, and the thickness a of the sleeve portion is 5 cm when the sleeve roller is used. It is necessary to be above.

As the outer shape of the side looper roller, generally a flat roll shape as shown in FIG. 2 or a zigzag shape is known, but as shown in FIG. The outer diameter from the bottom to the bottom,
That is, when the inclined surface is formed, the effect of suppressing the vertical deflection of the wire rod is good, and the wire passability in the side looper can be further stabilized.

[0045]

EXAMPLES Examples will be described below.

[0046]

Example 1 In a continuous rolling line for producing a soft steel wire rod having a C content of 0.08% or less, a side looper between an intermediate rolling mill and a finishing rolling mill was used in the present invention with a conventional cemented carbide (CoMo steel) roller. A comparison was made using a certain silicon nitride roller and a side looper roller made of a sialon roller.

As these rollers, solid rollers having an outer diameter D of 10 cm as shown in FIG. 3 were used. The diameter of the wire was 10 mm and the temperature was 900 ° C.

The results are summarized in Table 1. All of the cemented carbide rollers were worn for 90 days, which was a replacement criterion of 1 mm or more, and cracks / dots were peeled off on the surface. The surface of the wire was also affected by the surface properties of the roller, and roughened, resulting in deterioration of quality.

On the other hand, the silicon nitride roller of the present invention,
The sialon roller hardly worn even after 200 days of use, and it was possible to stably produce high-quality wire rods.

The rollers of the present invention all have a density of 97% of the theoretical density.

[0051]

[Table 1]

[0052]

Example 2 In a continuous rolling line for manufacturing a hard steel wire rod containing 0.30 to 0.60% of C, the present invention is a conventional cemented carbide roller with a side looper between an intermediate rolling mill and a finishing rolling mill. For comparison, a silicon nitride roller and a sialon roller were used.

The roller had a sleeve shape as shown in FIG. 4, and had an outer diameter D of 13 cm and a thickness a of 5 cm. Wire diameter is 10mm, temperature is 1100
It was ℃.

The results are summarized in Table 2. All of the cemented carbide rollers were worn for 1 day or more, which is a replacement standard, after 80 days, and cracks and spots were peeled off on the surface. The surface of the wire was also affected by the surface properties of the roller, and roughened, resulting in deterioration of quality.

On the other hand, the silicon nitride roller of the present invention,
The sialon roller hardly worn even after 200 days of use, and it was possible to stably produce high-quality wire rods.

[0056]

[Table 2]

[0057]

The side looper roller of the present invention is excellent in resistance to thermal shock and mechanical shock and has a long service life.
Since the roller surface properties can be kept good for a long period of time, it is possible to improve the productivity of the wire rod and stably produce a high quality wire rod for a long time.

[Brief description of drawings]

FIG. 1 is a side view of a roller provided with an inclination from a wire rod contact portion to a bottom portion of a side face of a side looper roller, which can suppress vertical runout of a wire rod in a side looper and more smoothly pass wires.

FIG. 2 is an explanatory diagram of an outer shape of a side looper roller.

FIG. 3 is an explanatory view of a side looper roller having a solid roller shape and shaft portions formed at both ends.

FIG. 4 is an explanatory view of a side looper roller formed by fitting and mounting shafts on both ends of a hollow portion.

[Explanation of symbols]

 1 Wire rod 2 Side looper roller 3 Shaft 4 Hollow part

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 5, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

Initially, carbon steel was used for the side looper roller, but it has been aimed to use rolls having higher hardness. In recent years, CrMo steel and further cemented carbide (WC) have been used.
-Co) rolls have come to be used (Reference: Japanese Patent Laid-Open No. 62-57707).

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction content]

[0046]

Example 1 In a continuous rolling line for manufacturing a soft steel wire rod having a C content of 0.08% or less, a conventional cemented carbide (WC-Co) roller and the present invention were used as a side looper between an intermediate rolling mill and a finishing rolling mill. For comparison, a silicon nitride roller and a side looper roller made of a sialon roller are used.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0051

[Correction method] Change

[Correction content]

[0051]

[Table 1]

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0056

[Correction method] Change

[Correction content]

[0056]

[Table 2]

Claims (1)

[Claims] 1. A silicon nitride or sialon 93-9
A side looper roller for rolling a hot wire rod, which is formed into a roll with a sintered body containing 9.5%.