JPH06145888A - Roll for rolling - Google Patents

Abstract

PURPOSE:To make excellent the wear resistance, surface roughening resistance, crack resistance and engaging properties in a roll for rolling by constituting the outer shell layer of the roll for rolling subjected to centrifugal casting of a specified compsn. of C, Si, Mn, Cr, Mo, V and Fe. CONSTITUTION:Casting is executed by a centrifugal casting method to obtain a roll for rolling. The chemical compsn. of its outer shell layer is constituted of, by weight, 1 to 3% C, <=2% Si, <=1.5% Mn, 3 to 15% Cr, <=8% Mo and 2 to 10% V and furthermore constituted of, at need, one or more kinds among <=2% Ni, <=10% W and <=10% Co, and the balance substantial Fe with inevitable impurities. In this way, the roll for rolling in which the friction coefficient measured by a rolling simulator is regulated to >=0.30 which is the value higher than the friction coefficient of the conventional material by 20 to 30%, slips are eliminated, engaging properties are good, the engaging critical angle is regulated to 20 deg., the area ratio of carbides is regulated to 7 to 20% and hardness is regulated to 75 to 85Hs can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling roll, and more particularly to a rolling roll suitable for use as a work roll before a rough stand and a finishing stand in a hot strip mill. The diameter is about 1000 for the former.
˜1270 mm, the latter approximately φ650-850 mm.

[0002]

2. Description of the Related Art The properties required for a work roll before a rough stand and a finishing stand in a hot strip mill are (1) wear resistance, (2) skin resistance, and (3).
Crack resistance, and (4) rolling property or stripability. This (4) rolling property or stripability will be described in more detail. (4-1) Bite, (4-)
2) Plate bending and (4-3) plate warping are included, but the oxide scale generated on the roll surface lowers the friction coefficient between the roll and the material to be rolled, causing slippage and worsening bite. It has been known.

[0003]

However, the material of the roll that has been conventionally used is adamite, high Cr cast iron or high alloy grain cast iron. Adamite is C
About 1.7 wt%, Cr about 1.5 wt%, hardness Hs5
Although it is 0 to 55, there is a problem in the resistance to skin roughness. High Cr cast iron has a C content of about 2.7% by weight, a Cr content of about 18% by weight, and a hardness of Hs 70 to 75, but also has problems with skin resistance and slippage. Further, the high alloy grain cast iron has C 3.3 wt% or so, Cr 1.8 wt% or so, and hardness Hs 75 to 85.
However, there is a problem in skin resistance, crack resistance, or accident resistance.

Therefore, it is an object of the present invention to change the material of the roll to a high speed steel which is excellent in abrasion resistance, skin resistance and crack resistance, and further to provide a rolling roll excellent in biting property.

[0005]

As a result of various experiments conducted on the biting property, the inventor has developed a rolling roll having an improved friction coefficient, less slippage, and excellent wear resistance.

The rolling roll of the present invention is a rolling roll cast by the centrifugal casting method, wherein the chemical composition of the outer shell layer is C1 to 3%, Si2% or less, Mn1.5% or less, and Cr3 to 15%, Mo 8% or less, V2 to 10%, the balance consisting essentially of Fe and unavoidable impurity elements, and the friction coefficient measured using a rolling simulator is 0.30 or more, which is 20 to 30 from the friction coefficient of the conventional material. % Large, no slippage, good biting property, biting limit angle is 20 °, carbide area ratio is 7 to 20%, hardness is Hs
75-85.

[0007]

[Action]

(A) C: 1 to 3.5% C is an element that constitutes a carbide necessary for improving wear resistance. If it is less than 1%, the amount of carbide crystallized is insufficient and sufficient abrasion resistance cannot be obtained. On the other hand, if it exceeds 3.5%, the amount of carbides becomes excessively large, resulting in brittleness and deterioration in crack resistance and skin roughening resistance.

(B) Si: 2% or less Si is effective as a deoxidizer, but if it exceeds 2%, the material becomes brittle, which is disadvantageous.

(C) Mn: 1.5% or less Mn is also a deoxidizing agent similar to Si, but also has an effect of fixing S as MnS. However, if it exceeds 1.5%, the material becomes brittle, which is inconvenient.

(D) Cr: 3 to 15% Cr is added to improve hardenability, strengthen the matrix and form a hard M ₇ C ₃ system carbide. If the addition amount is less than 3%, the effect due to the addition is not sufficient. On the other hand, if it exceeds 15%, the amount of harder VC carbides becomes too small, so the Cr amount is made 15% or less.

(E) Mo: 8% or less Mo is added to improve hardenability and temper hardness. However, when it is added in excess of 8%, the formation of M ₂ C-based or M ₆ C-based carbides increases, and harder VC carbides decrease.

(F) V: 2 to 10% V is an element having a very strong carbide forming action, and hard V
It forms C carbide and contributes most to improving the wear resistance of the rolling roll. When the V content is less than 2%, the crystallization of VC carbide is not sufficient. On the other hand, when the content of V exceeds 10%, the molten metal is largely oxidized and casting defects occur, and
When centrifugal casting, the VC has a low specific gravity due to its centrifugal force.
Carbides segregate in the inner part and become unhealthy.

(G) Other chemical components In the present invention, in addition to the above-mentioned chemical components,
Further, Ni may be contained by 2% or less. Since Ni stabilizes austenite and improves hardenability, it is preferable to add Ni particularly in the case of manufacturing a large roll. But,
If it exceeds 2%, the austenite is excessively stabilized, and it becomes difficult to decompose the retained austenite, so that the hardness and wear resistance cannot be sufficiently obtained.

Further, in addition to the above chemical components, W may be contained in an amount of 10% or less. W acts similarly to Mo and improves the tempering hardness. However, when added in a large amount, crystallization of M ₂ C-based or M ₆ C-based carbides increases, the carbides coarsen and toughness decreases, and harder VC decreases.

Further, in addition to the above chemical components, Co
Can be contained up to 10%. Co improves the adhesion of oxide scale generated on the roll surface during rolling and improves the skin resistance. It also improves high temperature strength, that is, heat resistance. These effects are set to 10% or less in consideration of saturation at about 10% and economic efficiency.

[0016]

The present invention will be described in more detail with reference to the following examples.

With respect to the materials of the present invention having the compositions shown in Table 1, adamite cast iron and high Cr cast iron, the molten metal was 70 mm in diameter and 80 in height.
A small roll material for a rolling simulator (rolling wear test) was cast by injecting it into a mm ₂ CO ₂ sand mold. This material is quenched from 1000 to 1100 ° C and 500 to 550
After heat treatment of tempering at 0 ° C., a sleeve-shaped test roll having an outer diameter of 60 mm, an inner diameter of 35 mm and a length of 40 mm was prepared. The metal structure of the roll material of the present invention thus obtained is shown in FIG. It is composed of a tough, high-hardness base (dark part) and hard carbide (white part).

[0018]

[Table 1]

The results of measuring the hardness of the surface of each test roll with a Shore hardness tester are shown in Table 2. It can be seen that the material of the present invention has a higher hardness than the comparative materials adamite cast iron and high Cr cast iron.

[0020]

[Table 2]

Next, in order to measure the area ratio of carbide on the roll surface, the metal structure of the alumina-finished finish was observed. The measurement results are also shown in Table 2. It can be seen that the carbide area ratio is higher in the order of adamite cast iron, the material of the present invention, and high Cr cast iron.

Further, a rolling wear test of the test roll was conducted by a simulator. As shown in FIG. 2, the simulator (rolling wear tester) includes a rolling mill 1, an upper roll 2 and a lower roll 3 incorporated in the rolling mill 1, a heating furnace 4 for preheating the rolled material S, and a rolled material S. It consists of a cooling water tank 5 for cooling, a winder 6 for applying a constant tension during rolling, and a tension controller 7 for adjusting the tension.
The test conditions are as follows. Rolled material: SUS 304, thickness 1 mm, width 15 m
m Rolling distance: 800 m Rolling temperature: 900 ° C. Reduction ratio: 25% Rolling speed: 150 m / min Roll cooling: Water cooling

The rolling load was measured during the rolling wear test. The measurement results of the rolling load are shown in Table 2 together with the friction coefficient μ and the biting angle θ calculated from these values. The coefficient of friction μ is
Inventive material, adamite cast iron, high Cr cast iron, in that order,
It can be seen that the material of the present invention has excellent biteability. Particularly, in the rolling wear test for high Cr cast iron, it was found that slip frequently occurred.

The depth of wear on the surface of the test roll was measured using a stylus surface roughness meter (SURFCOM). Table 2 also shows the results of obtaining the average wear depth by averaging the wear depth in each roll for each roll. It can be seen that the material of the present invention has the smallest average wear depth and is excellent in wear resistance. On the other hand, it can be seen that the adamite cast iron has extremely poor wear resistance. In order to evaluate the long skin, stylus surface roughness meter surface roughness R _{ma x} of the strip after rolling (SURFCO
M). The obtained results are also shown in Table 2.

[0025]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain a roll for rolling which has better wear resistance than conventional rolls and is superior in biting property. This means improvement of the roll unit (rolled amount / roll drum diameter), extension of roll life,
This reduces the frequency of roll replacement, contributes to economic efficiency, and contributes to the operational safety of the hot strip mill by improving the biting property.

[Brief description of drawings]

FIG. 1 is a microstructure photograph showing a metal structure of a roll material of the present invention.

FIG. 2 is a diagram schematically showing a rolling wear tester used for a roll wear test.

[Explanation of symbols]

 1 Rolling Machine 2 Upper Roll 3 Lower Roll 4 Heating Furnace 5 Rolled Material 6 Winding Machine 7 Tension Controller S Rolled Material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Hattori 1-9-1 Kitahama, Wakamatsu-ku, Kitakyushu City, Fukuoka Prefecture Inside the Wakamatsu Plant, Hitachi Metals, Ltd.

Claims (7)

[Claims] 1. In a rolling roll cast by a centrifugal casting method, the chemical composition of the outer shell layer is C1 to 3% by weight.
Si 2% or less, Mn 1.5% or less, Cr 3 to 15%, M
o 8% or less, V2 to 10%, the balance consisting essentially of Fe and unavoidable impurity elements, the friction coefficient measured using a rolling simulator is 0.30 or more, 20 to 30% larger than the friction coefficient of the conventional material, A rolling roll having no slippage, good biting property, a biting limit angle of 20 °, a carbide area ratio of 7 to 20%, and a hardness of Hs 75 to 85. 2. The rolling roll according to claim 1, wherein the chemical composition of the outer shell layer further contains Ni 2% or less by weight. 3. The rolling roll according to claim 1, wherein the chemical composition of the outer shell layer further contains W10% or less by weight. 4. Any one of claims 1 to 3
The rolling roll as described in No. 5, wherein the chemical composition of the outer shell layer further contains Co10 or less in a weight ratio. 5. The inner layer material is ductile cast iron.
To the rolling roll according to claim 4. 6. The rolling roll according to any one of claims 1 to 4, wherein the inner layer material is gray cast iron. 7. The rolling roll according to claim 1, wherein the inner layer material is graphite steel.