JPH03184610A - Flaw eliminating method for rolling roll - Google Patents

Abstract

PURPOSE:To prevent the generation of a buckling flaw in the case of cold rolling of a strip by forming a recessed part generated by local grinding of a roll, in a shape like a groove which makes a round in the rotational direction of the roll. CONSTITUTION:A roll 2 in which a recessed part 5 is formed by eliminating a flaw generated on the peripheral surface of the roll is integrated into a rolling mill and cold rolling of a strip is executed. In this case, since the recessed part 5 is formed in a shape of a groove which makes a round in the rotational direction of the roll, a boundary of the recessed part 5 and the surface of the roll does not exist in the turning direction of the roll. Therefore, since a work roll 3 does not receive a shock, a buckling flaw is not generated.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is a method for removing defects such as tart that occur on rolls other than work rolls, such as backup rolls and intermediate rolls of cold rolling mills that manufacture strips of steel materials. , relates to a method of removing by local grinding.

[Prior Art] A surface flaw called a buckle may occur on a cold-rolled strip of steel or the like. This flaw occurs across the entire width of the sheet at right angles to the rolling direction, and one of the causes is the convexity that occurs at the insertion part when the tip of the strip is inserted into the groove of the reel drum and the strip is wound around the reel drum. It is known that it occurs in some parts of the body. For this reason, a method is also known in which the tip of the strip is directly wound around the reel drum without being inserted into the reel drum.

[Problems to be Solved by the Invention] However, even when rolling is carried out by winding the tip of the strip directly around the reel drum as described above, buckling flaws are observed, especially in materials with good gloss such as stainless steel strip. There was a problem in that the quality of rolled products was significantly impaired.

An object of the present invention is to prevent the occurrence of buckling defects during cold rolling of strip.

[Means for Solving the Problems] As a result of various studies on the causes of occurrence of buckling defects, the present inventor found that buckling defects have a causal relationship with the peripheral surface shape of rolls other than work rolls, such as backup rolls and intermediate rolls. did.

In other words, if flaws such as cracks occur on the circumferential surface of the roll,
If rolling is carried out with these cracks left unattended, there is a risk that the cracks will expand and the rolls will be damaged, making rolling impossible. Therefore, it is necessary to remove the cracks by grinding or the like. Methods for removing cracks include a method of grinding the entire circumferential surface of the rolling roll and a method of grinding only the cracked portion. However, the method of grinding the entire circumferential surface of the roll has problems such as a reduction in the roll diameter, resulting in a shortened roll life and an increase in the number of grinding steps, as well as an imbalance in the roll diameter between the upper and lower rolls due to the reduction in the roll diameter.

Therefore, in the past, only the flawed part was locally ground as shown in Fig. 5, and the ground part was the local recess 1.
becomes. When such a roll 2 was installed in a rolling mill and rolled, bending defects occurred particularly in the shiny strip.

The present invention provides a method for removing flaws generated on the circumferential surface of a roll other than a work roll of a cold rolling mill by local grinding of the roll, in which a groove circumferentially circumferentially forms a recess formed by the local grinding in the rotational direction of the roll. This is a method for removing flaws from a rolling roll, characterized by forming the roll into a shape.

The cold rolling mill to which the present invention is applied has four stages, upper and lower, and upper-'l'
Various cluster type cold rolling mills including 6-high cold rolling mill and Sendzimir rolling mill. Further, in the present invention, rolls other than work rolls refer to intermediate rolls and backup rolls.

Hereinafter, the present invention will be explained in detail with reference to the drawings. Reference numeral 2 shown in FIG. 1 is a roll serving as a rolling roll on which scratches formed on the circumferential surface of the roll are removed by abrasion, and 5 is a recessed portion after the flaws formed on the roll 2 are removed by grinding. The recess 5 is formed in the shape of a groove that goes around in the rotational direction of the roll. A plurality of recesses 5 may be provided when the plurality of flaws generated on the roll circumferential surface are shifted in the roll axis direction.

The width of the recess 5 does not have to be uniform in the circumferential direction of the roll 2,
For example, as shown in FIG. 2, the width may be changed continuously from Wl to w2. However, as shown in FIG.
If the width does not change continuously from Wl to W2, cracks will occur in part A due to stress concentration. Therefore, when changing the width of the recess 5, it is necessary to change it continuously. In addition to cutting with a lathe and grinding with a grinder, known means can be used to remove the flaws.

[Function] As shown in FIG. 1, the roll 2 with the recesses 5 formed by removing the flaws formed on its circumferential surface is installed in a rolling mill, and a strip is cold rolled. At this time, as shown in FIG. 3, since the four portions 5 are formed in the shape of a groove circumferentially in the rotational direction of the roll, there is no boundary between the four portions 5 and the roll surface in the rotational direction of the roll. For this reason, the work roll 3 is not subjected to shock and therefore does not suffer from buckling or flaws.

When conventional local grinding as shown in Fig. 5 is performed, the recess 1
Since the boundary between the work roll and the roll surface exists in the rotational direction of the roll, the work roll receives a shock when it comes into contact with this boundary, and this is thought to be the cause of the buckling flaw.

[Example: The plate thickness was 0.6 mm and the plate width was 12 mm using a Kozenzimir rolling mill.
A 75 mm thin stainless steel plate was cold rolled. At this time, a countersunk intermediate roll with a diameter of 233 mm was used, in which cracks occurring in the center in the axial direction of the roll were removed by grinding using the following two methods.

As an example of the present invention, a concave portion formed by removing flaws on the circumferential surface of a dish intermediate roll was formed in the shape of a groove that goes around the roll in the rotational direction of the roll.

The width of the recess was 65 mm and the depth was 1.8 mm. When this countersunk intermediate roll was installed in a rolling mill and rolled, no bending defects were produced in the product after rolling. As a comparative example, the flaws on the circumferential surface of the intermediate roll are 1.5 mm deep and 55 m wide.
Grinding was performed with a length of 40 mm. When this countersunk intermediate roll was installed in a rolling mill and rolled, the rolled product had continuous bending defects in the board width direction at a pitch of 734 mm, resulting in a second-class product.

[Effects of the Invention] According to the present invention, it is possible to prevent the occurrence of buckling defects in cold-rolled strips, which has been a serious problem in the past. Particularly in the case of stainless steel strips, where surface gloss and flatness are important, it is possible to prevent deterioration or scrap, greatly contributing to quality improvement and cost reduction.

In addition, the method of grinding the entire circumferential surface of the roll requires a large number of roll grinding steps and reduces the roll diameter, which shortens the roll life. Furthermore, since the roll diameters are unbalanced between the upper and lower rolls, a large amount of inventory is required to achieve this balance, or grinding is required to match the roll diameters. In contrast, the present invention requires fewer roll grinding steps and does not reduce the roll diameter, making it possible to extend the life of the roll by about twice as compared to the above. Furthermore, there is no need for a large number of inventories or roll grinding in order to balance the roll diameters between the upper and lower rolls.

[Brief explanation of drawings]

Figures 1, 2, and 3 are diagrams for explaining the method of the present invention, Figures 1 and 2 are diagrams for explaining the method for removing scratches from rolls, and Figure 3 is for explaining the method of rolling by the method of the present invention. A side sectional view showing the state of contact between the work roll and the roll (A-A in Figure 1)
Fig. 4 is a diagram illustrating an example other than the present invention, and Fig. 5 is a front view illustrating a conventional method for removing flaws from a rolling roll. 2... Roll, 3... Work roll, 4... Strip, 5... Concave part

Claims (1)

[Claims] 1. In a method for removing defects generated on the circumferential surface of a roll other than the work roll of a cold rolling mill by local grinding of the roll, the recesses caused by the local grinding are formed in the shape of a groove that goes around the roll in the rotational direction of the roll. A method for removing flaws from a rolling roll, characterized by: