JPS6096716A - Surface hardening of current passing roll for electro-zinc plating - Google Patents

Abstract

PURPOSE:To improve service life of the roll by improving wear resistance, by a method wherein the surface of the roll is subjected to press working by utilizing the hardening properties of the roll body part of cold working to form a work-hardened layer on its surfce. CONSTITUTION:The surface of the roll body part comprising austenitic corrosion resistant alloy is cold worked by pressing its surface, then the outer diameter of the roll is reduced by over 0.01mm. to form work-hardened layer on the roll surface. Thus, wear resistance at the roll surface is improved, and the life is elongated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for hardening the surface of current-carrying rolls for electrogalvanizing, and in particular improves the service life of the roll by forming a work-hardening layer on the surface of the roll body to increase wear resistance. It is something.

Continuous electrogalvanizing is carried out by passing the steel sheet to be plated through the bath at a predetermined speed (for example, 70 to 100 m/min) while bringing the steel sheet into contact with energized rolls arranged in the bath. As shown in FIG. 2, the current-carrying roll consists of a roll body (sleeve) (1) and roll ends (2), (2) fitted on both ends of the sleeve and welded together.

Hanuteroy C-276, a nickel-based stainless steel alloy, is generally used for the body (1) of the current-carrying roll in consideration of its electrical conductivity, corrosion resistance to plating baths (such as zinc sulfate baths), and wear resistance. It is manufactured by machining the cast or forged sleeve material (solution heat treated). In terms of corrosion resistance, this alloy exhibits excellent corrosion resistance even in a severely acidic galvanizing bath and can withstand sufficiently as a current-carrying roll. but,
From the point of view of wear resistance, the surface hardness is at most Hv.
The hardness of the steel plate to be plated (usually Hv
Since it is softer than the 200 (approximately 200 mm, and may reach 250 mm), there is a problem that the chest surface is easily scratched during continuous use, especially the parts that come in contact with the edges on both sides of the steel plate. be.

Scratches on the roll surface cause uneven plating and deteriorate plating quality.

Therefore, if a scratch occurs on the roll surface, the line operation must be interrupted each time to replace the roll with another roll. In addition, mirror polishing is required in order to perform [ILF polishing on a scratched roll and reuse it, which requires a large amount of cost. There is a strong demand for extending the continuous service life of rolls until they require repolishing, thereby reducing roll maintenance costs, and improving the total lifespan of rolls.

The present invention meets the above requirements.

The method of the present invention utilizes the cold work hardening characteristics of the roll body to press and process the surface to form a hardened layer, thereby improving the continuous service life and total life of the roll.

The present invention will be explained in detail below.

The pressing process in the present invention is carried out by, for example, installing an energized roll on a lathe and moving it over the curved surface of the body while pressing a roller or bearing instead of a lathe cutting tool with a required reduction blade under the rotation of the roll. It will be done. Instead of a roller or a bearing, a cutting tool without a cutting edge may be used and the required pressing force may be used to make sliding contact with the circumferential surface of the body.

In pressing, the hardness of the surface of the roll body after processing and the depth of the hardened layer depend on the degree of processing (the amount of reduction in the outer diameter of the roll). In order to prevent the occurrence of surface scratches during actual use and extend the continuous service life, it is necessary to have a hardness higher than that of the steel plate to be plated, which is the mating material, and since pressing requires surface polishing after processing, the hardened layer is The layer thickness is the polishing allowance (usually about 0.2 to 0.5
mm) or more. From these points,
The amount of reduction in the outer diameter of the roll body due to pressing is 0.01.
It is desirable that the thickness is not less than mm.

FIG. 1 shows an example of the hardness distribution in the thickness direction of the roll body due to cold pressing. The sample was a hollow cylindrical roll body material (centrifugal casting product) made of Hastelloy 0-2.76, which was machined to a body diameter of 300 mm, and then pressed with a roller while rotating on a lathe. be. In the figure, the curve (
(11) is the diameter reduction fil O, O'
lPm1 (iiD is 0.08 mm, (N is 0.08 mm)
Bitscanu hardness for 05mm (measured load 200I)
represents. As shown in the figure, when the diameter is reduced by 0.01 mm or more, it is sufficiently hardened by processing, and the hardened layer reaches a depth of 1 mm or more, so there is no problem even if the outermost layer with the highest hardness is removed by polishing. It turns out that there is no. For example, if we look at the case where the diameter reduction amount is 0.0: L mm, the hardness of the surface after removing the surface layer of 0.2 to 0.5 mm, which is normal polishing, is Hv 260 to 270, which is normal. The hardness is sufficiently higher than that of the steel plate to be plated.

In order to further improve the wear resistance of the roll surface, it is necessary to increase the processing pressure during pressing depending on the work hardening characteristics of the roll body and the hardness of the plated steel plate, which is the mating material during actual use, to reduce the amount of diameter reduction due to processing. Generally speaking, the amount of diameter reduction due to machining is 1. 0 mm is sufficient, and there is no particular need for strong processing beyond that, and the cost burden required for such processing is also large.

The pressing on the roll surface of the present invention is performed in the roll manufacturing process. In addition, after being put into actual use, repolishing is repeated depending on the occurrence of scratches, corrosion, etc. on the roll surface due to use, and the thickness of the hardened layer gradually decreases. At this time, pressing may be carried out at an appropriate time depending on the remaining amount of the hardened layer.

Pressing is a processing method that uses rollers, bearings,
Alternatively, in addition to the method of using a cutting tool without a cutting edge, hammering such as peening, shot blasting, etc. can also be applied. Instead of these methods, in the case and energizing roll manufacturing process, a method is used in which the outer surface of the body material is work-hardened by drawing it through an outer die before it is assembled into the roll. May be applied.

In addition to the above-mentioned Hastelloy, the material of the roll body may be various austenitic corrosion-resistant alloys such as 18-8 stainless steel, which has the electrical conductivity and corrosion resistance necessary for a current-carrying roll, and does not have work hardening properties. good.

Although there is a concern that corrosion resistance will decrease if the degree of cold working is increased, there is no practical problem at all if the application is limited to electrogalvanizing. Incidentally, the above-mentioned pressing was carried out using a specimen taken from the outermost layer of the processing test material (diameter reduction: 0.05 mm) in a zinc sulfate bath (adjusted to pI 42.0 by adding sulfuric acid to znSO440Gg/l, liquid temperature 70°C). The results of the immersion test (20 days of immersion) show that there is no substantial change in the corrosion resistance before and after processing. It has also been confirmed that there is no problem with electrical conductivity.

Example 1 Hastelloy 0-2 centrifugally cast as body material
76 (Cr16.5%, Mo 17.1%, F853%
, W8.7'ly, balance Ni) was subjected to solution heat treatment by a conventional method, and then the inner and outer diameters were machined to the required dimensions, and a separately prepared roll end was fitted into it and welded 4 times. Assemble into rolls. While rotating this roll on a lathe, the surface of the body is pressed with a roller, and the outer diameter is adjusted to 0.
The diameter was reduced by 0.8 mm, and then the surface was polished (processing cost: 0).
．． 04mm) L,, finished product (body outside diameter 300mm
) was obtained. The roll surface hardness is Hv302.

This current-carrying low V) was put to practical use in a continuous electrogalvanizing line. The surface hardness of the steel plate to be plated is Hv18
0 and the transfer rate is xoom/min.

In this actual use, no scratches were observed on the surface of the roll after 6 months of continuous use, and the surface condition was such that it could be used continuously for several months.

Note that the continuous service life of conventional low)v (Hastelloy C-276> under the same plating conditions is about 1 to 3 months.

Example 2 18-8 austenitic stainless steel (Ci O, 02%, Si 1.15φ
,MnO,889&,Po,01t%,SO,010
Chi, 0r19.79&, Ni9.7'%, Mo2.2%
, the balance was Fe).

However, the amount of diameter reduction during pressing is 0.02 mm, the polishing allowance after pressing is 0.3 mm, and the roll surface hardness is IIv 260.

This R/L/W was subjected to a continuous electrogalvanizing line under the same plating conditions as in Example 1. Its continuous service life is two months (about two weeks for conventional rolls made of the same material). Due to the re-polishing and pressing process, it was repeatedly used, and each time it was used continuously for two months.

As described above, according to the present invention, 11iJ on the roll surface
Improved abrasion resistance prevents damage such as scratches on the surface, significantly improving roll life. Its continuous service life before requiring re-polishing is more than four times that of conventional rolls made of the same material. For example, Hastelloy C! -276 material can be used continuously for about one year, which is several times longer than conventional materials, which cannot exceed three months. Improving the continuous service life reduces the frequency of line operation interruptions for roll replacement, and significantly reduces roll regrinding costs.

In addition, by performing pressing at the appropriate time during re-polishing, the total lifespan until the roll is discarded can be improved. The effect of improving the total life of rolls that require expensive materials such as Hastelloy is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the hardness distribution in the thickness direction of the roll body, and FIG. 2 is a partially cutaway front view showing an example of an energized roll. 1: roll body, 2: roll end. Agent Patent Attorney Shinhachibe Miyazaki

Claims (2)

[Claims] (1) A method for hardening the surface of a current-carrying roll for electrogalvanizing, which comprises pressing or processing the surface of a roll body made of an autenite corrosion-resistant alloy to form a work-hardened layer on the surface. (2) The surface hardening method for a current-carrying roll for electrogalvanizing according to item (1) above, wherein the pressing step involves reducing the outer diameter of the roll by 0.01 mm or more.