JPH0776743A - Cermet guide roller - Google Patents

Abstract

PURPOSE:To provide a cermet guide roller excellent in heat resistance, impact resistance, toughness and wear resistance. CONSTITUTION:A cermet guide roller having an allay compsn. consisting essentially of TiC and/or TiN (TiCN solid solution is available to be sure) having low density, contg., as a binder, 25 to 60wt.% Fe group metals and moreover contg. WC, TaC and/or NbC, Mo2C, VC, Cr carbides or the like, and in which, in its physical properties, density is regulated to <=12g/cm<3>, hardness is regulated to 80 to 87 by a HRA scale and the average value of the crack length (micron) is regulated to <=50 is prepd.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present description relates to a guide roller used when rolling a wire rod, a steel bar and the like.

[0002]

2. Description of the Related Art Conventionally, cemented carbide has been mainly used for a so-called guide roller, which plays a role of guiding a member to be rolled to a predetermined position of a rolling roll in a rolling process of a wire rod, a steel bar, a flat plate and the like. . However, since the cemented carbide is composed of WC and Co, it has a very ^high density of 13 g / cm ³ or more. For this reason, the moment of inertia becomes large, and 5 to 1
It is not possible to sufficiently follow the speed of the work piece sent at a speed of 00 m / sec, which often causes a difference between the peripheral speed of the guide roller and the work piece speed. When such a difference occurs, a scratch due to the surface of the workpiece is scratched, which is a serious problem.

For this reason, various low density materials (for example, ceramics) have been conventionally studied for use as guide rollers. However, the properties required for the guide roller are very strict, such as heat resistance, thermal shock resistance, high toughness, and high wear resistance. This is because the guide roller plays a role of intermittently guiding the workpiece, which is generally heated to 500 to 1100 ° C., to the rolling roller. It is the fact that a material having a relatively low density and / or satisfying the required characteristics of ~ has not been found in conventional materials.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As a result of intensive studies to solve the above problems, the present invention has a lower density than conventional cemented carbide and / or heat resistance, impact resistance, toughness, The present invention provides a cermet guide roller having excellent wear resistance.

As the alloy composition, TiC and / or TiN having a low density (of course, a TiCN solid solution is also acceptable) is used.
-70% by weight based on 25 to 60% by weight of Fe group metal as a binder, 0 to 30% by weight of WC for improving toughness and TaC and / or NbC for improving heat resistance. Of 0 to 20% by weight, Mo ₂ C for improving sinterability of 0 to 10%, VC for microstructure refinement of 0 to 10% by weight, and Cr carbide for improving heat resistance and corrosion resistance of 0 to 10% by weight. It is contained.

[0006]

[Function] By selecting the above composition, the density can be reduced to 12
g / cm ³ or less, preferably it is possible to 10 g / cm ³ or less, problems, i.e., a difference occurs between the speed of the peripheral speed and the workpiece guide rollers, of the workpiece Machining scratches can be greatly reduced.

Next, the hardness of the above composition is HRA80.
It is possible to set the hardness to 87, and this range of hardness is practically desirable. That is, when the HRA is less than 80, the abrasion resistance is poor, and the operation is frequently stopped and the guide roller is replaced. Also, HRA8
If it exceeds 7, the toughness is lowered, and it often breaks due to impact with the work piece or repeated thermal shock.

As a result of various studies on evaluation of toughness, it was found that evaluation by crack length is the simplest and highly reliable. With the cermet of the present invention, cracks can be set to 50 or more, and almost zero in some cases. If the crack length exceeds 50 μm, the toughness deteriorates, thermal cracks are likely to occur mainly due to repeated thermal stress, and stress acts on these thermal cracks, resulting in a fracture accident.

Further, the reason for limiting the numerical values of the alloy composition capable of developing such a characteristic cermet will be explained. First, if the content of TiC and / or TiN is less than 20% by weight, sufficient reduction in density cannot be expected. On the other hand, if it exceeds 70% by weight, the toughness deteriorates and the crack length exceeds 50 microns.

When WC exceeds 30% by weight, the reduction in density is not exhibited. TaC and / or N
With respect to bC, even if it exceeds 20%, no further improvement in heat resistance can be expected, and only increasing the density is against the object of the present invention, so it was set to 20% or less. 1 for Mo ₂ C
If it exceeds 0%, heat resistance and oxidation resistance will decrease, so 10%
Below. When the VC exceeds 10%, the toughness decreases, so the VC is set to 10% or less. When the content of Cr carbide exceeds 10%, the toughness is lowered similarly to VC, so the content is made 10% or less. For Fe group metals, 25
If it is less than 60%, the toughness is lowered, and if it exceeds 60%, the wear resistance is inferior, so the range is set to 25 to 60%. Hereinafter, a detailed description will be given based on examples.

[0011]

Example: Each raw material powder was made of 28% TiC, 12% TiN,
_{WC12%, TaC4%, Mo 2} C2%, Co28%,
After mixing with a ball mill on the day of Ni 14%, it was dried, and after pressing, it was dried in vacuum at 1400 ° C. for 1 hour. The physical properties of the obtained cermet material are as follows: density 7.16 g / cm ³ , hardness H
RA and crack length were 0 micron.

A guide roller was prepared using the cermet material thus obtained. The test was carried out on the Morgan Block Mill No. 23 stand. When the surface of the guide roller was observed after the rolling treatment for 300 tons, the wear condition was good, and although very fine thermal cracks had occurred, no large thermal cracks leading to fracture were generated. Also, the surface of the rolled product was good, and no scratches were observed due to the difference between the peripheral speed of the guide roller and the passing speed of the rolled product.

The cermet materials shown in Table 1 were prepared in the same manner as in Example 1.

[0014]

Table 1 Materials TiCN WC TaC Mo ₂ C VC Cr ₂ C ₃ Co Ni 1 22 10 10 2 1 0 30 30 25 2 68 0 4 2 1 0 12.5 12. 5 3 40 0 4 2 1 0 30 30 23 4 40 28 4 2 0 0 13 13 13 5 50 10 10 0 2 1 0 10 27 6 5 50 10 18 2 1 0 10 10 10 7 40 10 4 0 1 1 1 22 22 22 8 40 10 4 8 1 1 18 18 9 40 40 10 4 2 0 1 20 23 10 10 40 10 4 2 8 1 17 17 18 11 40 10 4 4 1 1 0 23 20 12 12 40 10 4 2 1 8 25 15

The physical properties of each material are shown in Table 2.

[0016]

Table 2 Materials Density (g / cm ³ ) Hardness (HRA) Crack length (microns) 1 8.1 80.1 0 2 6.0 88 52 3 3 6.9 80 0 4 7.7 80.2 40 5 6.7 80.8 5 6 6.1 89 89 67 7 7.2 7.2 83 0 8 7.2 82 8 5 9 7.2 82.5 0 10 6.9 84 7 7 11 7.2 82.7 10 12 6 .7 83.7 0

From the above results, except for Material 6, the composition is an alloy within the scope of the present invention. Example 1 using the above materials
Similarly to the above, when a guide roller was prepared and tested, good results were shown except that Samples 2 and 6 were fractured, and in particular, processing flaws did not occur on the rolled object.

[0018]

As described above, since the cermet guide roller of the present invention is lightweight, a difference between the peripheral speed of the guide roller and the rolling speed of the material to be rolled is unlikely to occur, and therefore, a processing flaw is unlikely to occur on the material to be rolled. . In addition, it has excellent impact resistance, thermal shock resistance, and abrasion resistance due to its composition, and can exhibit long life characteristics without cracking accidents.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area C22C 29/02

Claims (2)

[Claims] 1. A density of 12 g / cm ³ or less, preferably 10 g / cm ³ or less, and a hardness of 80 to 8 on the HRA scale.
Cermet guide roller having a crack length (average of crack lengths (microns) occurring at corners when 50 kg is loaded with a Vickers hardness meter) of 50 or less, preferably 25 or less, in the range of 82 to 86. . 2. The composition of cermet according to claim 1, wherein TiC and / or TiN ... 20 to 70 wt% WC ... 0 to 30 wt% TaC and / or NbC ... 0 to 20 wt% Mo ₂ C 0 to 10 wt. % VC 0-10% by weight Cr additive 0-10% by weight Co and / or Ni 20-60% by weight Cermet guide roller.