JPH06210324A - Intermediate roll for cold rolling - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an intermediate roll for cold rolling excellent in wear resistance. [Structure] In the cold rolling intermediate roll, a trivalent chromium composite plating layer having a thickness of 5 to 20 μm in which hard particles are dispersed is formed on a nickel plating layer having a thickness of 0.3 to 2 μm formed on the surface of the roll. Has been done. Since the average particle diameter and eutectoid amount of hard particles are suppressed to an appropriate size, the plating does not peel off and a nickel plating layer with an appropriate thickness is used.
Combined with the valent chromium composite plating, it exhibits high peeling resistance and abrasion resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate roll for cold rolling, and more particularly to an intermediate roll for cold rolling having excellent wear resistance.

[0002]

2. Description of the Related Art One of the properties required for cold rolling intermediate rolls is wear resistance. Conventionally, the hardness of the roll material is increased by adding Cr, heat treatment, etc. to improve wear resistance. Recently, in order to improve wear resistance, chrome plating is also performed on the roll surface. Among the chromium plating, for example, hexavalent chromium plating is performed, for example, “Materials and Processes” (3 (1990), 1350).
And “Materials and Processes” (5 (1992), 511) and the like are known. Regarding trivalent chromium plating,
"Hardness of chrome plating from chromium (III) sulfate-potassium formate bath" (Matsufumi Takatani et al., Metal Surface Technology, 10
-37 (1986), 621) is known. Furthermore, regarding trivalent chromium composite plating, "Cr-SiC
Preparation and Wear Properties of Composite Coatings "(Matsufumi Takatani et al., Metal Surface Technology, 3-38 (1987), 97) and" Cr-SiC, Cr-Diamond composite coating from trivalent chromium plating bath "(Matsufumi Takatani et al. Metal Surface Technology, 11-37 (198
6), 671) and the like are known. In the latter document, degreasing when a steel plate is subjected to trivalent chromium composite plating,
It is described that after the pickling, the surface treatment of Ni strike is performed.

[0003]

The intermediate roll for cold rolling is subjected to a large reduction force and frictional force, and rolls and slides on the work roll and other roll surfaces. Therefore, when the above-described technique of forming a nickel plating layer on a steel sheet and forming a trivalent chromium composite plating layer on it is simply applied to an intermediate roll for cold rolling, the plating layer is easily peeled off and worn. Was there. For this reason, the intermediate roll for cold rolling has a short life, and the roll unit is reduced, resulting in a high product cost. Further, in the cluster roll type rolling mill, the intermediate roll is driven to indirectly drive the work roll. When the intermediate roll wears, slippage may occur and torque transmission may not be possible.

The present invention is intended to provide an intermediate roll for cold rolling which is excellent in wear resistance.

[0005]

An intermediate roll for cold rolling according to the present invention is a hard roll having an average particle size of 5.0 μm or less on a nickel plating layer having a thickness of 0.3 to 2 μm formed on the roll surface. 5 to 20 particles were dispersed at an eutectoid amount of 13 wt% or less
A trivalent chromium composite plating layer having a thickness of μm is formed.

Forged steel, chrome steel or the like is used as the roll base material. As hard particles, SiC, ZrB ₂ , Si
₃ N ₄ , Al ₂ O ₃ , Cr ₃ C ₂ , B ₄ C, CBN, and diamond. Multiple types of hard particles may be dispersed in the chrome plating matrix. There are an electrolytic method and an electroless method as the plating method, but the electrolytic method is preferable in consideration of the efficiency of the plating operation and the efficient co-deposition of the dispersant. Further, in order to uniformly disperse the dispersant in the plating bath, a chemical method using a surfactant or a physical method using air stirring is used.

When the nickel plating thickness is less than 0.3 μm or more than 2 μm, the peel resistance is not effective. If the average particle diameter of the hard particles dispersed in the trivalent chromium composite plating exceeds 5.0 μm or the amount of eutectoid exceeds 13 wt%, the plating is likely to peel off. When the trivalent chromium composite plating thickness is less than 5 μm, the peeling resistance is good,
Abrasion resistance deteriorates. On the contrary, when the trivalent chromium composite plating thickness exceeds 20 μm, the peeling resistance deteriorates.

[0008]

The binding force of nickel at the interface with the roll base material and chromium is higher than the binding force at the interface of trivalent chromium with the roll base material. Improves the bond strength (adhesion) with the valent chromium composite plating. In the trivalent chromium composite plating, the hardness of the matrix is 800 to 1600 Hv and the hardness of the hard particles is 2000 Hv or more. The higher the coating hardness of the plating is, the higher the abrasion resistance is. Therefore, it is preferable that the eutectoid amount of hard particles is large. However, when the co-deposition amount of the hard particles becomes too large, the binding force between the matrix and the hard particles becomes small. Since a large rolling force and frictional force are applied to the hard particles during rolling, the plating is easily peeled off. In the present invention, the average particle size and the amount of eutectoid particles of the hard particles are suppressed to appropriate values, so that the plating does not peel off due to the force applied to the protruding portion of the hard particles. From these facts, the trivalent chromium composite plating roll exhibits high peeling resistance and abrasion resistance.

[0009]

[Example] In order to clarify the effect of ultra-hard Cr-SiC dispersion plating on wear resistance, a roll rolling wear experimental device (test piece: φ80 mm × 10 mm, mating piece: φ160 mm × 1)
5 mm, slip ratio: 0.0%, mating piece heating temperature: 200
° C, pressing load: 70 kgf, rotation speed: 3000 rpm,
The experiment was performed using cooling: water lubrication). Forged steel (SUJ-2) was used as the material of the test piece and the mating piece.

The plating baths shown in Table 1 were used. Ni pre-plating thickness is 1μm, composite plating thickness is 20μ
m. The average grain size of SiC was 0.7 μm, the eutectoid amount of SiC was about 4 to 5%, and the roughness of the roll was 0.
It was 3 μmRa. Further, a heat treatment of 200 ° C. × 20 Hr was performed. A conventional forged steel roll (roll roughness: 0.3 μmRa) was used as a comparative material.

[Table 1]

Polishing, degreasing, pre-plating, trivalent chromium composite plating, and heat treatment were sequentially performed to prepare a test piece.

Using a roll rolling wear tester, the effect of the number of rollings on wear resistance (roughness reduction resistance) was investigated.
The result is shown in FIG. Since the intermediate roll is often replaced at about 0.10 μm, the roll life is more than four times that of the conventional technique, judging from the results of this experiment.

Here, a concrete example of cold rolling of a steel sheet will be described. Using the following work rolls and intermediate rolls, ordinary steel plates (plate thickness: 1.1 mm, plate width: 250 mm, length:
250 m) was subjected to multi-pass cold rolling. The rolling length was set to 3 km, and the surface roughness of the intermediate roll at that time was investigated.

Work roll Roll size Diameter: 150 mm Width: 400 mm Roll base material C: 1% Cr: 3% Si:
0.6% S: 0.4% Mo: 0.3% Fe: Residual surface hardness 800Hv Surface roughness 0.29 μm Ra Intermediate roll Roll size Diameter: 150 mm Width: 400 mm Roll base material C: 1% Cr: 3% Si:
0.6% S: 0.4% Mo: 0.3% Fe: Residual pre-plating Nickel plating thickness: 0.6 μm Composite plating Matrix: Trivalent chromium Plating thickness: 10 μm Dispersed particles: SiC Average particle size: 3 μm Eutectoid amount : 4 wt% Surface hardness 800 Hv Surface roughness 0.20 μm Ra Rolling speed was about 80 m / min, and rolling reduction was 20 to 30%. Further, a beef tallow rolling lubricant was used as the lubricant.

As a result of rolling under the above conditions, the surface roughness of the intermediate roll was 0.20 μm Ra.

As a comparative example, forged steel intermediate roll (same size,
Composite plating has dispersed particles: SiC average particle diameter: 5.6 μm
Cold-rolling was carried out under the same rolling conditions as described above with an eutectoid amount of 15 wt% and a surface roughness of 0.20 μm Ra). As a result, peeling occurred at a rolling length of 500 m.

[0017]

Since the intermediate roll for cold rolling of the present invention is excellent in peeling resistance and abrasion resistance, the roll unit is improved by extending the roll life. Furthermore, by shortening the roll reassembling time, improving the roll unit, and reducing the number of rolls held, it is possible to improve productivity and reduce manufacturing costs.

[Brief description of drawings]

FIG. 1 shows the relationship between the number of rolls rolling and the surface roughness of a roll,
It is a diagram which compares and shows this invention and the prior art.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Shiraishi 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd. Technology Development Division (72) Inventor Matsuo Ataka 20-1 Shintomi, Futtsu City, Chiba Prefecture Shinnihon (72) Inventor, Kouei Nakajima 20-1 Shintomi, Futtsu City, Chiba Prefecture Nippon Steel Co., Ltd., Technology Development Headquarters (72) Inventor Kazuo Kanemaru Akasaka Coast, Kitakyushu, Kitakyushu, Fukuoka Prefecture 2-1 Ishikawa Metal Industry Co., Ltd. (72) Inventor Ryoji Sato 495-143 Niijima, Fukushima, Wakamatsu-ku, Kitakyushu City, Fukuoka Prefecture Fujimura Industry Co., Ltd.

Claims (1)

[Claims] 1. An intermediate roll for cold rolling, the roll surface of which is chromium-plated, the average grain size of which is 5.0 μm or less on a nickel plating layer of 0.3 to 2 μm thickness formed on the roll surface. An intermediate roll for cold rolling, characterized in that a trivalent chromium composite plating layer having a thickness of 5 to 20 µm in which hard particles are dispersed in an amount of eutectoid of 13 wt% or less is formed.