JPH02190440A - Guide roll for hot rolling - Google Patents

Abstract

PURPOSE:To obtain a guide roll for hot rolling excellent in deformation resistance and seizure resistance by constituting a guide roll of a sintered compact containing a hard phase of double boride of Ni and Mo, double boride of Ni and W, double boride of Mi, Mo, and W, etc., and a binding phase of Ni and Mo. CONSTITUTION:A guide roll for hot rolling is constituted of a sintered compact consisting of a hard phase composed principally of one or more kinds among double boride of Ni and Mo, double boride of Ni and W, and double boride of Ni, Mo, and W and a binding phase composed principally of Ni and Mo. It is preferable that the hard phase comprises 50-80wt.% of the above sintered compact. The above sintered compact is prepared by mixing respective powders, e.g. of alloy, such as Mo-B, Ni-B, and W-B, and simple substance, such as Ni, Mo, W, and B, in the prescribed ratio, compacting the resulting powder mixture, and then sintering the resulting green compact in vacuum or in an atmosphere of Ar, H2, etc., at about 1100-1500 deg.C. Then, this sintered compact is subjected to grinding work to the prescribed shape and size so as to be formed into the guide roll. By this method, the long-life guide roll for hot rolling excellent in resistance to oxidation, seizure, deformation, wear, and impact can be obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a guide roll for hot rolling wire rods, that is, a roll used to guide hot rolled wire rods in manufacturing steel wire rods, etc. It is something.

[Prior Art] Many guide rolls are used in the process of manufacturing wire rods by rolling red-hot steel materials in multiple stages. Several types of materials are used for these guide rolls depending on the usage conditions. For example, WC-Go is used in the finishing stage, but because of its short life, a large amount of guide rolls are consumed.

[Problem to be solved by the invention] Guide rolls for hot rolling directly receive red-hot steel material on the inlet or outlet side of the rolling roll, and are generally required to have excellent oxidation resistance and seizure resistance. be done. Furthermore, since the surface condition of the guide roll used in the wire finishing process is directly reflected in the finished condition of the wire rod as a product, it is also required to have excellent deformation resistance and abrasion resistance at high temperatures. For this reason, it is not possible to obtain products with good surface conditions using Fe-based materials used in earlier processes, and WC-
A guide roll made of Co is used. WC-Go
Because it does not have sufficient oxidation resistance or deformation resistance at high temperatures, it is used while being cooled with a large amount of cooling water, and the surface of the guide roll is alternately exposed to red-hot steel and cooling water. As a result, after a short period of use, cracks occur on the surface of the guide roll, and these cracks are also transferred to the surface of the wire. Therefore, it is necessary to frequently replace the finishing guide roll, and there is a strong desire to extend the life of the guide roll.

On the other hand, guide rolls made of sintered ceramics have been proposed to meet the requirements for oxidation resistance and deformation resistance at high temperatures, but because the impact resistance is not sufficient, the tip of the high-speed rolled wire rod It has not been put into practical use because of problems such as chipping when hitting the ball. Further, ceramic-coated metal rolls have been considered, but cannot be used because they do not essentially improve deformation resistance at high temperatures and the adhesion of the coating is insufficient.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems.
A guide roll for hot rolling, characterized in that it is composed of a sintered body consisting of a hard phase mainly composed of one or more kinds of O, W complex borides, and a binder phase mainly composed of Ni and Mo. This is what we provide.

Note that the complex boride sintered body that is the material of the hot rolling guide roll of the present invention is known as boride cermet, but it is a ceramic-metal composite material similar to WC-Go. Therefore, a significant increase in lifespan was unexpected.

The guide roll of the present invention can be obtained by the method described below. For example, MoB, WB, and Ni powders are ground and mixed in an organic solvent such as ethanol using a rotary bot mill, a vibration mill, or the like. After drying this powder, it is pressure-molded using a metal press or a rubber press, and then heated in a vacuum or under Ar, Hz
1100-1 in an inert or reducing atmosphere such as
A sintered body is obtained by heating to about 500'c for a certain period of time or more. The sintered body thus obtained is processed into a predetermined shape and size using a diamond grindstone or the like to obtain a guide roll.

The raw material powder used to obtain the sintered body is not necessarily the above-mentioned Mo
It is not necessary to use a combination of B, WB, and Ni powder;
-8 alloy powder and Mo powder, ■ powder or Ni, Mo.

A combination of a single metal powder of W and a powder of B may also be used. In addition to these main raw materials, IC, Tic
It is also possible to add metal carbides such as TiN, TaN, etc., and metal nitrides such as TiN and TaN.

The structure of the material constituting the guide roll of the present invention will be explained as follows.

It is desirable that the binder phase is distributed so as to surround the hard phase, and that the hard phases are not continuous but independent. The hard phase has a polygonal shape with a not very large vertical to horizontal ratio, and the average particle size is 5 μm or less. The maximum width of the bonded phase is about 5 μm, and it is distributed almost uniformly.

In addition, looking at the specific microstructure of the sintered body, no matter which combination of raw materials is used, the hard phase is mainly MoJiB* or W2N1B* or (Mo, W)JiBg, and the mainly Ni-Mo alloy. It consists of a binder phase, and the weight percent of this hard phase is preferably 50 to 85%. The reason why it is preferable to set the ratio of the hard phase to 50 to 85% by weight is that if the hard phase is less than 50% by weight, the deformation resistance of the guide roll surface at high temperatures will not be sufficiently improved, and if it is more than 85% by weight, the wire rod This is because cracks are likely to occur due to thermal shock during running. Note that a particularly preferable ratio of the hard phase is 55 to 80%.

In contrast to the hard phase, the binder phase is mainly composed of Ni and Mo, and it is preferable that most of the binder phase, for example, 85% or more, be composed of one or two of these or an alloy phase. This is because the Ni and Mo binder phase has a wide solid solution range with the hard phase at high temperatures, unlike the hard phase of the complex boride mentioned above, and is optimal for ensuring mutual interfacial strength. . on the other hand,
Mo is effective in improving the solid solution strength and hardness of the Ni phase, and does not react with the hard phase to form lower borides.
The appropriate amount of Mo in it is 5 to 20% by weight, and even 10% by weight.
-18% by weight is more preferred.

It is preferable that the surface of the guide roll of the present invention is as smooth as possible. On the other hand, it is also possible to perform surface treatments such as plating, thermal spraying, and overlaying on one surface, and in some cases, the life can be further extended.

[Function] Complex boride, which is the main component of the sintered body constituting the guide roll according to the present invention, essentially exhibits less decrease in hardness and strength at high temperatures than tool steel, and is compatible with Ni-Mo metal. Even so, its characteristics are clearly demonstrated. Furthermore, the interface between the hard phase and the binder phase of this sintered body is very strongly connected, and the strength and hardness of the sintered body are inevitably high even at high temperatures.

For this reason, it becomes possible to weaken the cooling of the guide roll during wire rolling, and the thermal shock received by the guide roll becomes relatively small. Therefore, the occurrence of cracks on the guide roll surface is suppressed, and the life of the guide roll is significantly extended. Furthermore, if the cooling amount is reduced, there is a concern that the guide roll and the wire will seize; however, the hard phase present on the guide roll surface not only improves the seizure resistance, but also reduces some of the B contained in the hard phase. After it is liberated and oxidized, it forms an extremely thin glass-like layer along with scale, which functions as a lubricant. Therefore, the seizure property of the guide roll according to the present invention with the wire rod is significantly improved compared to the conventional guide roll.

[Example] (Example 1) Mo843%, W87%, Ni 45% and Mo
Using 5% of each powder as raw materials, Ni-Mo, N1-W
A sintered body having a Ni-Mo-W complex boride content of 68% by weight was prepared, and a guide roll was manufactured. When this guide roll was used as a guide roll on the rolling entrance side in the finishing process of carbon steel wire rod, it could be used for 34 hours until scratches appeared on the surface of the wire rod, which were thought to be caused by cracks in the roll. In addition, when the hardness of this roll was measured, Hv = 830 kg/mm2 at room temperature and 4 at 800°C.
80 kg/mm”.

(Examples 2 to 6 and Comparative Examples 1 to 2) After producing a sintered body and manufacturing a guide roll in the same manner as in Example 1, an actual machine test was conducted in the same manner as in Example 1. The results are shown in Table 1. show.

(Comparative Example 3) As shown in Table 1, a conventional WC-Go gold alloy guide roll was prepared and tested in the same manner as in Example 1.

[Effects of the Invention] As described above, the guide roll according to the present invention is superior to the conventional WC-Go in terms of deformation resistance at high temperatures and seizure resistance with workpieces.
Compared to guide rolls using gold alloys, this is significantly improved and can achieve longer life. Therefore, the number of guide roll replacements during rolling of steel wire rods is greatly reduced, improving manufacturing efficiency and stabilizing product quality.

Claims (2)

[Claims] (1) Ni, Mo complex boride, Ni, W complex boride, and Ni
A guide roll for hot rolling, characterized in that it is composed of a sintered body consisting of a hardened phase mainly composed of one or more of complex borides, Mo, and W, and a binder phase mainly composed of Ni and Mo. . (2) The guide roll for hot rolling according to claim 1, wherein the weight percentage of the hard phase of the sintered body is 50 to 85%.