JPS6358054B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a rolling mill roll stand, and more particularly to a method of manufacturing a rolling mill roll stand manufactured by welding a plurality of extremely thick rolled steel pieces.

Conventionally, cast steel has generally been used as a material for rolling mill roll stands. However, when using cast steel, cavities and segregation occur within the cast steel as the roll stand becomes larger.
Moreover, there is a disadvantage that problems such as a decrease in strength due to this occurrence cannot be avoided.

On the other hand, as an alternative to cast steel, we use extra-thick rolled steel pieces with a uniform structure, cut out a part of the roll stand from this extra-thick rolled steel pieces, and stack and weld multiple pieces together to form a block. Furthermore, it has been proposed in Japanese Patent Publication No. 53-42453 to manufacture a roll stand by joining these blocks together by welding.

However, according to this method, in lap welding, the degree of restraint by the weld metal differs between the welding start side and the welding end side, resulting in a difference in the amount of welding shrinkage of the extra-thick rolled steel piece. For this reason, the material thickness after welding cannot be maintained uniformly, so the number of machining operations after block welding has to be increased.In addition, the increase in welding locations reduces the work efficiency and economy of roll stand manufacturing. There is a problem of significantly lowering the performance.
Furthermore, since both overlap welding and subsequent block integration welding are performed, large thermal deformations occur in the roll stand due to the double welding heat effect, and machining work to correct this increases, resulting in similar problems. However, there is a problem in that the work efficiency and economic efficiency of stand manufacturing are reduced. Furthermore, the material of the portion of the extra-thick rolled steel piece that is affected by this welding heat becomes brittle, which may impair the safety of the roll stand under the action of large rolling loads including impact loads.

An object of the present invention is to easily use an extra-thick rolled steel billet, reduce welding heat deformation during welding of extra-thick rolled billet pieces, and thereby provide a highly efficient rolling mill with extremely high dimensional accuracy. An object of the present invention is to provide a method for manufacturing a roll stand.

The present invention is characterized in that the upper block, lower block, and two posts of the rolling mill are each made of separate extra-thick rolled steel pieces, and each post is divided into a plurality of pieces in the longitudinal direction. The rolling mill roll stand is made of extremely thick rolled steel pieces, and the rolling mill roll stand is rolled over so that the two posts are vertically positioned one above the other. Manufacture of a rolling mill roll stand in which the abutting portions of rolled steel pieces are electroslag welded, and then the abutting portions of the ends of the posts and the abutting portions of the upper block and the lower block are joined by electroslag welding, respectively. It's in the method.

According to this method, the reverse bending is first applied to the post by electroslag welding on the center part, and then the amount of reverse bending can be canceled by deformation by electroslag welding on the other side, which greatly simplifies machining after integral welding. It is possible to improve work efficiency.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall perspective view showing a state in which the roll stand is electroslag welded, and FIG. 2 is a schematic diagram showing a deformed state of the roll stand after welding the central portion of the post.

As shown in the figure, the roll stand 1 is composed of an upper block 2, a lower block 3, and a left post 4 and a right post 5 disposed between the upper and lower blocks 2 and 3. The upper and lower blocks 2, 3 are each made from one extra-thick rolled steel piece, and the left and right posts 4, 5 are each made from two extra-thick rolled steel pieces 4a, 4b, 5a,
Consisting of 5b. In addition, the extremely thick rolled steel pieces constituting the left and right posts 4 and 5 are rolled so that the rolling direction coincides with the longitudinal direction of the posts (the direction in which the rolling load is applied), and the plates constituting the upper and lower blocks 2 and 3 are The thick rolled steel piece is arranged so that its rolling direction is perpendicular to the rolling direction of the post. Each extremely thick rolled steel piece is tack welded via an electroslag welding start tab plate 10, and is restrained and integrally formed.
Note that 11 is an end tab plate for electroslag welding.

The roll stand 1 that has been integrated in advance in this way is turned sideways with the left post 4 facing upward, and is placed on the base 13 via the support 12. In front of the roll stand, there is a rail 14 laid parallel to the stand, and on this rail 14, the nozzle 15 of the electroslag welding machine is run horizontally (left and right in FIG. 1), up and down, and
and a manipulator 16 that is freely movable in the front and rear directions.
is installed.

In this example, there are a total of six abutting portions of the extremely thick rolled steel pieces. The order of electroslag welding is as follows: abutting part A at the center of the post 5 located on the lower side in FIG. 1, then abutting parts B and C on both sides (whichever comes first);
Furthermore, it is preferable to carry out this process at the abutting portion D at the center of the left post 4 located on the upper side in the figure, and at the abutting portions E and F on both sides (whichever comes first). Furthermore, electroslag welding at each butt portion is performed from bottom to top to eliminate the influence of the melt flowing down. According to such an electroslag welding procedure, the influence of thermal deformation due to electroslag welding can be finally canceled. That is, when joining the two extra-thick rolled steel pieces 5a and 5b that make up the right post 5, when electroslag welding is performed from bottom to top at the abutting part A, which is the joining part between the two, first, the welded part Cooling progresses from the bottom to the top, and as this progresses, the molten zone contracts. At this time, a start tab plate 10 for restraining the extremely thick rolled steel pieces 5a and 5b is temporarily attached to the lower part of the abutting portion A, so that it acts to restrain shrinkage. Therefore, the amount of shrinkage of the molten part increases as the upper part of the abutting part A increases, and as shown by the solid line in FIG. A tensile force is generated that draws 5a and 5b toward each other, and as a result, the joined right post 5 is deformed upward into a concave shape as indicated by the dotted line in FIG. In this state, when electroslag welding the butt parts B and C, which are the joints between the end of the extra-thick rolled steel piece constituting the right post 5 and the upper block 2 and lower block 3, the same reason as mentioned above is achieved. As a result, in both abutting parts B and C, the upper melted part contracts from the lower part, so a tensile force is generated that pulls both ends of the right post 5 toward the blocks 2 and 3, respectively, and the right post 5 just moves upward. A bending force is applied in the direction of convexity. As a result, the concave bend of the right post 5 shown by the dotted line is corrected. This can also be said to mean that the right post 5 was given a reverse bend in advance during the first electroslag welding.

In this embodiment, first, the mating parts A, B, and C of the lower right post 5 are electroslag welded, but in this case, the upper left post 4 is welded as shown in FIG.
Since the upper openings of the butt parts D, E, and F can be left slightly open, the nozzle of the electroslag welding machine can be easily inserted, which has the advantage of improving work efficiency.

If the same welding procedure is performed for the electroslag welding of the upper left post 4 and the electroslag welding of the left post 4, upper block 2, and lower block 3, dimensional accuracy with less welding thermal distortion can be achieved. This means that a rolling mill roll stand with excellent properties can be easily manufactured.

Next, selection of the positions of the abutting portions B, C, E, and F will be explained. Stress concentration occurs at the four corners of the window of the roll stand during rolling, so we cut the inside (window side) of the upper and lower blocks.
Preferably, the abutting portions are separated from the corner portions.
Now, as shown in FIG. 3, let R be the radius of curvature of the corner of the lower block, H be the point at which the corner changes from an arc to a straight line, and I be the end of the abutting part. Generally, in electroslag welding, a member approximately 30 mm from the mating end I melts, and approximately 10 mm of the non-melted part adjacent to this melted part is affected by heat, reducing impact resistance. Therefore, it is preferable to separate the mating end from the inner surface of the lower block by at least 1=(R+40) mm. On the other hand, from the point of view of block machining,
The smaller the amount of cut, the better, but it is also possible to use the cut out member as a tab plate. In this case, there is an advantage that even if some of the weld metal from the tab plate flows into the roll stand during welding, there will be no deterioration in quality since the tab plate, block, and post are originally the same member. Considering the use as such a tab plate, practically speaking, 1 is about 50 to 300.

By the way, the upper block or the lower block is equipped with a lowering cylinder or a lowering screw, and it is desirable that the size of this mounting part be larger than that of other parts. In consideration of work efficiency, it is preferable to form a block by electroslag welding a member thicker than the post as an intermediate member 20 between two members having the same thickness as the post, as shown in FIG. 1.

By the way, as mentioned above, in the case of electroslag welding, the weld heat affected zone is approximately 40 mm, so at least defects can be removed from the surface of the extremely thick rolled steel piece by rolling.
It is necessary to confine more than 40mm inside. To achieve this, for roll stands of practical dimensions, the rolling ratio defined by the cross-sectional area ratio before and after rolling must be
It should be 1.3 or higher. On the other hand, if the rolling ratio is normally 5 or more, internal defects are compressed and the structure becomes uniform, but according to the embodiment of the present invention described above, internal defects are allowed as already explained in detail. Therefore, it is not necessary to set the rolling ratio to 5 or more. That is, in the embodiments of the present invention described above, the rolling ratio that can be practically used is 1.3 to 5.0.

For example, a large roll stand with the structure shown in Figure 1 has a width of about 3 m, a height of about 9 m, a stand thickness of about 60 cm, and a window width of about 1.5 m.
Basically, it has the advantage of being easy to manufacture with just six welds.

According to the method for manufacturing a rolling mill roll stand of the present invention as described above, it is possible to extremely easily manufacture a rolling mill roll stand with high dimensional accuracy and high efficiency by reducing welding thermal deformation of extra-thick rolled steel pieces. can be manufactured using extra-thick rolled steel billets.

[Brief explanation of drawings]

Figure 1 is an overall perspective view showing the manufacturing equipment for rolling mill roll stands, Figure 2 is a diagram for explaining the deformed state of the roll stand, and Figure 3 is for explaining the dimensions of the mating portion of extra-thick rolled steel billets. This is a diagram for 1...Rolling mill roll stand, 2...Upper block, 3...Lower block, 4, 5...Post,
A, B, C, D, E, F... mating part.

Claims (1)

[Claims] 1. A method for manufacturing a rolling mill roll stand composed of a plurality of extra-thick rolled steel pieces joined by welding, in which an upper block, a lower block, and two posts of a rolling mill are each separately assembled. The rolling mill roll stand is constructed of extremely thick rolled steel pieces, and each of the posts is composed of extremely thick rolled steel pieces that are divided into a plurality of pieces in the longitudinal direction. The abutting portions of a plurality of extremely thick rolled steel pieces constituting the post are electroslag welded while the post is turned over so that they are vertically positioned, and then the abutting portions of the end ends of the post and the upper block are welded. A method of manufacturing a rolling mill roll stand, characterized in that the abutting portions of the roll stand and the lower block are joined by electroslag welding. 2. In what is stated in claim 1,
A rolling method characterized in that after electroslag welding all of the abutting portions of the posts located on the lower side in the vertical direction, all abutting portions of the posts on the upper side in the vertical direction are electroslag welded. Method of manufacturing machine roll stand. 3 In what is stated in claim 1,
A method for manufacturing a rolling mill roll stand, characterized in that after the post, upper block, and lower block are temporarily attached, the electroslag welding is performed from below the abutting portion upwards. 4. The method for manufacturing a rolling mill roll stand according to claim 3, wherein the temporary attachment is performed using a tab plate. 5 In what is stated in claim 4,
A method for manufacturing a rolling mill roll stand, characterized in that the tab plate is a member cut out from the upper block or the lower block.