JPH0466649A - Working roll having high wear resistance and high brightness for cold rolling - Google Patents

Abstract

PURPOSE:To provide a work roll with both high wear resistance and high brightness by specifying the content of Cr, Mo, W, V and Co in a steel series roll. CONSTITUTION:The working roll for rolling is formed of a high-speed steel having a compsn. constituted of, by weight, 0.5 to 1.5% C, <=3.0% Si, <=1.5% Mn, 2 to 6% Cr, <=10% Mo, <=20% W, 1 to 5% V and 5 to 13% Co, if required, furthermore constituted of <=5% Ni and the balance Fe with inevitable impuri ties. Moreover, the hardness of the barrel of the roll is regulated to >=90HS, and the amt. of eutectic carbides in the structure is suppressed to <=20%. By the crystallization of the carbides of Cr, Mo, V, W or the like, its wear resis tance is improved. Furthermore, because the matrix is highly hardened and the difference in the hardness between the carbides and the matrix is reduced, its brightness is improved. At the time of using this roll for rolling, a sheet having high quality and high brightness can be obtd.

Description

[Detailed description of the invention] [Industrial application field] The present invention has high wear resistance in the field of cold rolling, and
The present invention relates to a cold rolling work roll used for rolling plate products with excellent brightness.

[Conventional technology]

Conventional work rolls for cold rolling are 1, for example,
Le C described in No. 7529: 0.7 to 1.1%,
Cr: 1.5-6% Copper-based material with addition of Mo, V, etc., or 10% Cr steel-based material similar to cold die steel JIS SKD-11, or high-speed steel JIS
Rolls made of materials similar to 5KH-54 were the mainstream.

In recent years, in the field of cold rolling, there has been an increasing demand for improved wear resistance of cold rolling work rolls from the standpoint of energy saving and productivity improvement. In contrast, roll materials are increasingly being made of cold die steel or high-speed steel. on the other hand,
Customers of sheet products are increasingly demanding improvements in the brightness of sheets such as stainless steel sheets and shadow mask materials. On the other hand, cold die steel materials have excellent wear resistance due to the crystallization of eutectic carbides in the form of a network, but the network-like eutectic carbides are transferred to the plate product, reducing the brightness of the plate product. It may cause deterioration. In addition, in high-speed steel materials, eutectic carbides are unevenly distributed and their area ratio is up to 30%, making it difficult to uniformly finely roll the roughness, and furthermore, MC Since the hard carbide, which is mainly composed of carbides, crystallizes, there is a large difference in hardness between the base and the carbide, so the wear of the base increases during rolling, and as a result, the roughness of the roll becomes rough, resulting in poor brightness of the plate. There was a drawback.

[Problem to be solved by the invention]

The present invention has been made for the purpose of solving the above-mentioned problems of the prior art and providing a work roll for cold rolling that has both high wear resistance and high brightness.

In general, to improve wear resistance, in addition to increasing the amount of carbide,
High hardness is effective. An effective means for increasing hardness is to increase the amount of Cr, Mo, etc. added. However, all of these elements lower the amount of C at which coarse eutectic carbides appear.

Therefore, increasing the amount of elements such as Cr and Mo for the purpose of increasing hardness crystallizes network-like eutectic carbides, which can improve wear resistance, but there is a limit in terms of grindability and brightness. In addition, since V, W, etc. generate hard carbides, increasing the hardness by increasing the amount of these elements makes it possible to increase the hardness while preventing coarse eutectic carbides. By crystallizing it, it becomes possible to improve the brightness of the plate. High-speed steel developed for cutting steel has excellent wear resistance and high brightness by adding appropriate amounts of V and W in addition to Cr and Mo. However, since there is a large difference in hardness between the crystallized carbide and the base, the wear of the base becomes large during rolling, which limits the improvement in brightness. Therefore, in order to obtain high brightness, it is effective to reduce the difference in hardness between the crystallized carbide and the base, and therefore it is necessary to increase the hardness of the base.

[Means to solve the problem]

The present invention is a work roll for cold rolling using a material developed from the above point of view to achieve the above object.

First, the reasons for specifying each component are as follows.

C is necessary for forming carbides to improve wear resistance and ensuring base hardness. When the amount is less than 0.5%, the amount of carbide is small and the wear resistance is not sufficient. Also, 1.
If it exceeds 5%, network-like eutectic carbides increase, causing problems in grindability and resulting in poor brightness.

Si is a necessary element as a deoxidizing agent and also improves tempering resistance. However, if the amount exceeds 2.0%, embrittlement tends to occur.

Mn has a deoxidizing effect and also has the effect of fixing impurity S as MnS, but if its amount exceeds 1.5%, the amount of retained austenite increases, making it difficult to maintain stable and sufficient hardness. Toughness also decreases.

If Cr is less than 2%, hardenability is poor, and if it exceeds 6%, Cr
The system carbide becomes excessive and crystallizes as a network-like eutectic carbide, which is disadvantageous in terms of brightness.

Mo and W are respectively M2C or.

It generates MsC-based carbide and also contains it in the matrix to strengthen the matrix and improve wear resistance and tempering resistance. However, if it becomes excessive, the toughness due to the addition of MBC-based carbides decreases. The upper limits of Mo and W are 10% and 20%, respectively, and it is desirable that 2 Mo + W is 20% or less.

V forms MC-based carbides and contributes to improving wear resistance, but
If it is less than 1%, there is no sufficient effect, and if it exceeds 5%, the grindability is significantly impaired.

Co dissolves in the matrix and is an effective element to increase resistance to temper softening and to obtain high hardness through high-temperature tempering through secondary hardening, but if it is less than 5%, the effect is small, and if it exceeds 13%, the toughness decreases. descend.

Note that the high-speed steel of the present invention may contain Ni in addition to the above-mentioned elements. Since Ni has the effect of improving hardenability, it can be added in an amount of 5% or less. Exceeding this will lead to an increase in the amount of retained austenite, resulting in a decrease in hardness and roughness resistance.

Elements other than the above are substantially composed of Fe, excluding impurities.

The main impurities are P and S, and it is desirable that both P and S be 0.1% or less to prevent embrittlement.

Next, the work roll according to the present invention is used for cold rolling, and the hardness of the body part is H in terms of wear resistance and dent resistance.
It needs to be 390 or more. Furthermore, in consideration of brightness and plate thickness accuracy, it is desirable that the hardness of the body is H593 or higher.

In addition, in order to prevent the grindability from significantly deteriorating compared to conventional rolls, the area ratio of carbides must be 20% or less. If the area ratio of carbide exceeds 20%, the carbide will drop off significantly during grinding, excessive scratches will occur, and a roll surface with a predetermined roughness cannot be obtained by grinding.

[Effect]

The work roll for cold rolling according to the present invention is made of Cr.

Abrasion resistance is improved by crystallization of carbides such as Mo, V, and W, and brightness can be improved by increasing the hardness of the base and reducing the difference in hardness between the carbide and the base. In addition, since the hardness of the base is increased, a hardness of 8590 or more can be stably obtained, so that it can be used as a work roll for cold rolling. Furthermore, since the area ratio of carbides can be suppressed to 20% or less, there is no significant deterioration in grindability.

〔Example〕

As an embodiment of the present invention, a trunk diameter of 290 ma+ and a trunk length of 19
A work roll for cold rolling of 00 nn was manufactured.

For comparison, a conventional roll was also manufactured with the same dimensions. Table 1 shows the chemical components of the roll of the present invention and the comparative roll.

Table 1 The roll of the present invention was heat treated at 11'OO to 1200°C and tempered at 500 to 550°C to obtain a body hardness of HS93. The comparison roll was also heat treated to have the same body hardness (H593).

A stainless steel plate was cold rolled using the roll of the present invention and a comparative roll, and the ratio of the roughness before rolling to the roughness after rolling was determined as the roughness reduction rate in order to compare the wear resistance. Shown below. In addition, in order to compare the brightness, the glossiness of the plate after rolling with the same thickness in the same pass was measured using a glossmeter, and the second
As shown in the figure. As is clear from FIGS. 1 and 2, the roll of the present invention has approximately twice the abrasion resistance and 1.5 times the brightness compared to the comparative roll.
It was confirmed that both brightness and brightness were excellent.

Further, the roll of the present invention was able to obtain a predetermined roughness without any particular trouble during grinding, and no scratches were generated that would pose a problem during rolling.

However, although the grinding time is approximately 1.2 times longer than that of the comparative roll, this cannot be said to be a significant deterioration of the grinding performance, and the roll can be used within normal grinding ranges.

〔Effect of the invention〕

According to the present invention, it is possible to produce a cold rolling work roll that has both extremely superior wear resistance and high brightness compared to conventional rolls. Therefore, it is possible to significantly improve the roll consumption rate,
Furthermore, if used for rolling plate products that require high brightness, high quality and high brightness sheets can be obtained.

[Brief explanation of the drawing]

Claims (1)

[Claims] 1. Weight ratio: C: 0.5 to 1.5%, Si: 3.0%
Below, Mn: 1.5% or less, Cr: 2 to 6%, Mo: 1
0% or less, W: 20% or less, V: 1 to 5%, Co: 5 to
It is made of high-speed steel with 13% Fe and the balance being Fe and unavoidable impurities, and has high wear resistance and is characterized by a body hardness of HS90 or higher and a structure with a eutectic carbide content of 20% or less. Bright cold rolling work roll. 2. Weight ratio: C: 0.5-1.5%, Si: 3.0%
Below, Mn: 1.5% or less, Cr: 2 to 6%, Mo: 1
0% or less, W: 20% or less, V: 1 to 5%, Co: 5 to
Made of high-speed steel consisting of 13% Ni, 5% or less Ni, and the balance Fe and unavoidable impurities, the hardness of the body is HS90.
The above-mentioned work roll for cold rolling has high wear resistance and high brightness, and is characterized in that the amount of eutectic carbides in the structure is 20% or less.