JPH03234307A - Manufacture of dull roll - Google Patents

Abstract

PURPOSE:To manufacture a dull roll with the excellent surface in wear resistance by performing laser treatment or electric discharge machining after plating the surface of roll with a specific element. CONSTITUTION:The surface of roll is beforehand plated with the element which formed to a solid solution in a melting state at a high temp. and which is precipitated or solid-solution hardened after solidification. After that, the plated surface is subject to the laser treatment or electric discharge maching. In this way, the roll with excellent wear resistance as the dull roll for cold rolling can be manufactured and the steel sheet which has good formability and gloss after painting at the same time can be rolled at a low cost and stably.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a dull roll for cold rolling steel sheets having excellent durability.

(Prior Art) Methods for manufacturing dull rolls for cold rolling steel sheets include methods for treating the roll surface with shot blasting, electrical discharge machining, or recently, laser irradiation. Rolls made by these methods have a larger surface roughness than normal rolls, so the height of the protrusions decreases more quickly and their lifespan is shorter. In the shot blasting method, work hardening is used, and in electric discharge machining and laser irradiation, the extreme surface is rapidly heated and cooled to increase surface hardness and extend life. However, the friction conditions during rolling are such that even the average surface pressure exceeds 100 kg/-, and
Since the rolls are harsh and involve slipping, the lifespan of dull rolls is less than half that of other rolls, as the protrusions are subject to higher local surface pressure than bride rolls.

A prior art related to a method for manufacturing dull rolls is, for example, Japanese Patent Publication No. 60-2156 (roll roughening device using laser light), but it does not mention a method for improving the durability of protrusions.

(Problems to be Solved by the Invention) An object of the present invention is to provide a surface dull roll that has much better wear resistance than conventional dull rolls for cold rolling.

(Means for Solving the Problems) The gist of the present invention to achieve the above object is as follows.

1. A method for manufacturing a surface dull roll, which comprises plating the roll surface with an element that dissolves in solid solution in a high-temperature molten state and precipitates or hardens in solid solution after solidification, and then performs laser treatment or electrical discharge machining.

2. Plating elements are Cr, Mo, Ni, and Ag.

The method for producing dull rolls according to claim 1, characterized in that one or more of TI, W, V, and Nb are used.

3. The dull roll manufacturing method according to claim 1, wherein the thickness of the plating layer is 1/10 to 1 times the required height of the dull protrusions.

The present inventors used an abrasion tester that can simulate the abrasion of a rolling roll to observe how the abrasion of the laser dull roll protrusion progresses.

As a result, we found the following. In normal steel, the protrusions are formed by melting by the laser beam, and at the same time, the surrounding area is lifted up like a crater by the blowing of assist gas, and then the base metal absorbs heat and solidifies rapidly. has a supersaturated solid solution metal structure. The molten layer is on the extreme surface and has a smaller heat capacity than the base material, so its cooling rate is extremely high. For this reason, the current roll material (1vt%C-3vt%Cr, forged steel) has a retained austenite structure and has low hardness. That is, the Vickers hardness of the molten layer when laser irradiated is around 700, which is 100 to 200 lower than that of the base material. For this reason, the protrusions that have been carefully built fall off due to plastic deformation or wear during the wear test process, and disappear after a small number of frictions.

However, the present inventors changed the material of the base material to high-speed tool steel,
As a result of conducting similar experiments using a material that undergoes precipitation hardening, such as maraging steel, it was discovered that the molten layer in which the alloying elements were supersaturated in solid solution became harder than the base material, improving durability. At this time, it is preferable to provide a tempering process using a multiple beam method or the like to promote precipitation of supersaturated solid solution alloy elements.

Based on these facts, we came up with the idea of applying plating before laser treatment in order to further enrich the molten layer with alloying elements. Chrome plating has already been put into practical use for bride rolls with small roughness. In the case of a dull roll, the protrusions are subject to significant wear, but if the protrusions are reduced by the above method and the flat parts are plated with chrome, the durability of the dull roll will be greatly improved. Furthermore, it is more economical to add elements only to the surface than to make the base material a high alloy.

Note that as the melting treatment after plating, electric discharge machining may be used in addition to laser irradiation.

Next, the types of elements to be plated are Mo in addition to Cr.

There are Ni, AfI, TI, V, Nb, W, etc.
All of them are elements that have a precipitation effect or a solid solution effect. Precipitates caused by these alloying elements are carbides (Cr
tC3, MO2C, W2C, etc.) and intermetallic compounds (Ni, Mo, Fe2Mo.

Ti, Al1, etc.).

The thickness of the plating layer is determined by the height of the protrusions produced after melting. Empirically, the protrusion height is approximately at the same level as the melting depth. Therefore, the plating layer thickness must be thinner than the melting depth. This is because it is necessary to mix with the base material and ensure adhesion to the base material. If the thickness of the plating layer is the same as the height of the protrusion, there will be little mixing of the base metal, and if the thickness of the plating layer is much thinner than the height of the protrusion, the mixing of the plated metal will be small and the degree of hardening will be small. This mixing ratio, along with the material of the base material, determines the hardness of the protrusion, adhesion to the base material, and other characteristics, so the optimal plating thickness should be determined depending on the type of precipitate used. However, the maximum protrusion height required for dull rolls is around Lots,
Since plating thinner than 1 kon is usually not done and has little effect, the lower limit was set to 1/IO of the protrusion height. From the above, the upper limit is 1 times the protrusion height.

These matters are shown in FIGS. 1 and 2. Figure 1 shows that hardened protrusions are generated by laser irradiation after plating to an appropriate thickness. (a) is a cross section of the surface layer after plating, and (b) is the surface after plating is irradiated with laser. The later surface layer is shown. FIG. 2 is a scanning electron micrograph illustrating that the height of the rolled solid origin of the dull roll is reduced due to plastic deformation and wear.

(Example) Three types of dull rolls, A, B, and C shown in Table 1, were prototyped and steel plates were cold rolled.

The relationship between the rolling distance of these rolls and the average height of the projections was as shown in FIG. It can be seen that the abrasion resistance of the roll of the present invention is two to three times that of the conventional roll. The method of measuring the protrusion height is as shown in FIG. 3, and is equal to about twice the center line average roughness.

(Effects of the Invention) Since the present invention is configured and operated as described above, it is possible to manufacture a roll having much superior durability as a dull roll for cold rolling compared to the conventional one.
A steel plate having both good formability and gloss after painting can be rolled stably at low cost.

[Brief explanation of drawings]

FIG. 1 is a process explanatory diagram of the present invention, and FIG. 2 is a scanning electron micrograph showing the plastic deformation or abrasion of the protrusions during rolling of the dull roll. FIG. 3 shows the roll of the present invention and the conventional roll.
It is a figure which shows the change of the protrusion height when performing cold rolling of a steel plate. Figure 3 fi Korenagako (J'7n) hand ft-, earlier amendment (spontaneous) June 2, 1990 l, indication of the case 1990 Patent Application No. 2 84 2, name of the invention Dalroll Manufacturing method 3, relationship with the case of the person making the amendment

Claims (1)

[Claims] 1. A surface dull roll characterized in that the roll surface is plated with an element that dissolves in solid solution in a high-temperature molten state and precipitates or hardens in solid solution after solidification, and then performs laser treatment or electrical discharge machining. manufacturing method. 2. Plating elements: Cr, Mo, Ni, Al, Ti, W
2. The method for producing dull rolls according to claim 1, characterized in that one or more of the following are selected from the group consisting of , V, and Nb. 3. The dull roll manufacturing method according to claim 1, wherein the thickness of the plating layer is 1/10 to 1 times the required height of the dull protrusions.