GB2196565A

GB2196565A - Welding base material and method and apparatus for forming the same

Info

Publication number: GB2196565A
Application number: GB08625731A
Authority: GB
Inventors: Shohei Kusada; Katsuaki Nakamura; Yasuhiko Yokokawa; Haruhiko Yasuhara; Kaoru Adachi; Yoshihiro Yamashita
Original assignee: Komatsu Ltd
Current assignee: Komatsu Ltd
Priority date: 1986-10-28
Filing date: 1986-10-28
Publication date: 1988-05-05
Also published as: GB8625731D0

Abstract

A welding base material is so formed that the portion to be welded to another welding base material has a thickness more than that of the other part. This assures that the welded structure has no reduction of strength after completion of welding operation. The welding base material is formed by rolling operation. An apparatus (15) for forming a welding base material includes means (16) for holding a plate (8), means (18) for rolling the end part of the plate while moving therealong and a heating means (17). <IMAGE>

Description

SPECIFICATION Welding base material and method and apparatus for forming the same The present invention relates to a welding base material preferably employable for forming a hollow elongated member which is constituted by a plurality of hollow unit pieces welded to one another and moreover it relates to method and apparatus for forming the welding base material of the above-mentioned type.

A boom for a power shovel is so constructed that for instance, first to third hollow unit pieces are jointed to one another by butt welding and brackets are welded to both the end parts of the boom. Generally, durability of the thus constructed boom is determined by fatigue strength as measured at the welded part of each of the hollow unit pieces.

Improved fatigue strength at the welded part is normally obtainable by increasing a thickness of the welded part to reduce average stress in this part. This means that a thickness of plate material constituting each of the hollow unit pieces is increased so as to increase an area where butt welding is achieved for the welded part of a hollow unit piece.

However, increased wall thickness of the whole elongated member leads to increased weight of the boom, causing an intensity of power required for turning the boom up and down to be increased. As a result, capability of digging and scraping operation to be performed by a power shovel decreases and thereby increasing operational cost.

Hence, the present invention has been made with the foregoing background in mind and its object resides in providing a welding base material which assures improved reliability of a welded joint part without any increase in weight of a hollow elongated member which is constituted by a plurality of hollow unit pieces welded to one another as well as method and apparatus for forming a welding base material of the above-mentioned type.

To accomplish the above object, there is proposed according to one aspect of the present invention a welding base material which is so designed that the end part of the base material at which a welding groove is prepared is formed to a thick walled portion having the thickness more than that of the rest of the base material.

Further, there is proposed according to other aspect of the present invention a method of forming a welding base material which is carried out by way of the steps of thrusting a roller against the end part of a plate-shaped member at which a welding groove is prepared and then displacing the roller relative to the plate-shaped member so as to allow the end part of the base material to be formed to a thick walled portion.

Further, there is proposed according to another aspect of the present invention an apparatus for forming a welding base material which includes plate holding means for holding a plate on the platform in the upright standing state and rolling means adapted to move along the one end part of the plate to form a thick walled portion by rolling the end part of the plate.

Other object, features and advantages of the present invention will become readily apparent from reading of the following description which has been prepared in conjunction with the accompanying drawings.

The accompanying drawings will be briefly described below.

Figure 1 is a perspective view of a boom usable for a power shovel; Figures 2 to 7 are an illustrative view respectively which shows how a hollow elongated member such as boom or the like is produced by using a plurality of welding base materials according to the present invention; Figure 8 is a perspective view of an apparatus for forming a welding base material; Figure 9 is a perspective view of a modified example of a work roll for forming a welding -base material; Figure 10 is a front view of another modified example of a work roll for forming a welding base material; Figure 11 is a side view of a welding base material usable for producing a hollow elongated member, wherein a base material is formed in accordance with another method of the present invention;; Figure 12 is a perspective view of a hollow elongated member having the rectangular cross-sectional shape in which four welding base materials in Fig. 11 are used, wherein the elongated member is shown in the provisionally asembled state before welding operation; Figure 13 is a side view of a frame which is produced by using the hollow elongated member in Fig. 12; Figures 14 and 15 are a sectional view respectively which shows how a boss portion is produced; Figure 17 is a plan view of a forming tool usable for a welding base material to form a boss portion; Figure 18 is a sectional view of the forming tool in Fig. 17, particularly illustrating how a hole on the plate is enlarged to produce a welding base material with a boss portion attached thereto;; Figure 19 is a side view of a boom for a power shovel which is constructed by using a plurality of welding base materials having the circular cross-sectional shape; Figure 20 is a perspective view of welding base materials having the circular cross-sectional shape usable for producing the boom in Fig. 19, wherein they are shown in the sec tioned state before welding operation; Figure 21 is a sectional view of the welding base materials having the circular cross-sectional shape in Fig. 20 which are welded to one another; Figure 22 is a vertical sectional view illustrating a press forming method in which inward pressing is achieved with the use of a die; Figure 23 is a vertical sectional view illustrating another press forming method in which outward pressing is achieved with the use of a die;; Figure 24 is a vertical sectional view illustrating a successive forming method in which upsetting is achieved with the use of rotational rolls; and Figure 25 is a vertical sectional view illustrating another successive forming method in which roll forming is achieved with the use of a die.

Now, the present invention will be described in a greater detail hereunder with reference to the accompanying drawings which illustrate preferred embodiments thereof.

Fig. 1 shows a boom for a power shovel by way of a perspective view. This boom is so constructed that a hollow elongated member 1 having the rectangular cross-sectional shape (hereinafter referred to as elongated member) is built by welding hollow three unit pieces 2, 3 and 4 having the rectangular cross-sectional shape to one another (hereinafter referred to as unit piece), brackets 5 and 6 made of cast steel are welded to both the ends of the elongated member 1 and boss members 7 are welded onto both the side walls of the elongated member 1.

The elongated member 1 is produced by way of the steps as mentioned below. First, the end part 8a of a plate 8 as shown in Fig.

2 is subjected to rolling and thereby a first half-finished product 10 having a thick walled portion 10 at the end part 8a as shown in Fig. 3 is obtained. The first half-finished product 10 is bent to the U-shaped configuration by press working and thereby a second halffinished product 11 as shown in Fig. 4 is obtained. Then, another second half-finished product 11 is placed on the second half-finished product 11 in correct vertical alignment in the reversed state and their joint portions 12 are fixedly connected to one another by welding operation whereby a third half-finished hollow elongated product 13 having the rectangular cross-sectional shaped is obtained.

The fore end of the thus produced third halffinished product 13 is beveled at the thick walled portion 9 thereof in such a manner as shown in Fig. 6 and another third half-finished product 13 of which fore end is beveled in that way is brought in contact with the firstmentioned third half-finished product 13 in the end-to-end relation. Thereafter, welding operation is performed along a welding groove as defined by both the beveled faces 14 whereby a required elongated member 1 is produced.

Fig. 8 shows by way of a perspective view a working apparatus 15 for working the plate 8 as shown in Fig. 2 to a first half-finished product (welding base material) 10 as shown in Fig. 3. The apparatus 15 essentially comprises plate holding means 16, heating means 17 adapted to move along the one end part 8a of the plate 8 to heat it and rolling means 18 adapted to move along the end part 8a subsequent to movement of the heating means 17 to form the thick walled portion 9 by rolling the end part 8a.

Specifically, the plate holding means 16 includes a first holder 20 on a platform 19 to firmly hold the plate 8 at both the surfaces 8b and 8c of the latter. The holder 20 comprises a stationary holding block 21 fixedly mounted on the platform 19, a movable holding block 22 movably mounted thereon and a hydraulic cylinder 23 for actuating the movable holding block 22, Thus, the first holder 20 is so constructed that the plate 8 is located between both the holding blocks 21 and 22 and it is then immovably held therebetween with the aid of the movable holding block 22 which is displaced toward the stationary holding block 21 by actuating the hydraulic cylinder 23.

Further, the plate holding means 16 includes a second holder 24 on the platform 19 to firmly hold both the side end faces 8d and Be of the plate 8 which is placed on the platform 19. The holder 24 comprises a pair of movable holding blocks 25 movably mounted on the platform 19 and hydraulic cylinders 26 for actuating the movable holding blocks 25. It should be noted that each of the blocks 25 is provided with a stopper plate 27 of which upper part is formed with a cutout 27a. Each of the stopper plates 27 is supported on the block 25 to move up and down and moreover it is normally urged in the upward direction under the effect of resilient force of a spring 28.Thus, the second holder 24 is so constructed that the holding blocks 25 are displaced by actuating the hydraulic cylinders 26 until the stopper plates 28 come in contact with both the end faces 8d and Be of the plate 8 which has been held by the first holder 20 whereby the plate is held immovably.

The heating means 17 includes a gateshaped frame 29 which is so designed that it is located above the plate 8. The frame 29 is equipped with two burners 30 on the inside wall thereof which are mounted on the latter in the inclined state so as to allow their flame to be oriented toward a single point.

The heating means 17 is so constructed that the frame 29 is displaced along the plate 8 immovable held on the platform 19 while the upper end part 8a of the plate 8 is heated by the full length thereof by means of the burners 30.

The rolling means 18 also includes a gate shaped frame 31 which is located above the plate 8. The frame 31 is equipped with a pair of thickness limiting rollers 32 on the inside wall thereof of which rotational axis is directed upward. It should be noted that the rollers 32 are displaceable toward and away from one another in order to change a distance therebetween. Further, the frame is equipped with a working roller 33 on the inside wall thereof. The working roller 33 is supported on a horizontal shaft and assures the portion where it is located between both the rollers 32. The working roller 33 can be displaced up and down so that it is normally brought in pressure contact with the upper end face 8f of the plate 8.

Prior to working of the plate 8 by operating the working apparatus 15 dummy pieces 34 of which material and thickness are determined same as those of the plate 8 are provisionally attached to the upper faces of both the end parts 8d and Be of the plate 8 in such a manner that they have the same height as that of the plate B and the latter is immovably held on the platform 19 with the aid of the plate holding means 16. Next, the heating means 17 is displaced across the upper end part 8a of the plate 8 to heat the latter and thereafter the rolling means 18 is displaced across the same to roll the upper end face 8f of the plate 8.

Owing to the fact that the dummy pieces 34 are provisionally attached to the end parts of the plate 8 prior to working of the latter there is no possibility of producing any burr along the side edges of the plate 8 with the use of the working apparatus. However, it is often found that burr is produced along the working ends of the plate 8 when rolling work is conducted without any restrictive holding of the working side ends of the plate 8. Further, it is found that when the working ends of the plate 8 are firmly caught directly by means of the stopper plates 27, they are subjected to rolling and thereby they are deformed. When they have a thickness more than that of the stopper plates 27, burr is produced in the area where they swell out therefrom. In the case of the working apparatus of the invention burr is produced on the dummy pieces 34 but no burr is produced on the plate 8.After completion of rolling work on the plate 8 the dummy pieces 34 are removed from the latter by cutting operation.

Since the stopper plate 27 is disposed to move up and down in the working apparatus 15, it is depressed by means of the roller 33 when the latter rides on the stopper plate 27, resulting in no occurrence of damage or injury on the roller 33.

Incidentally, the present invention should not be limited only to a combination of the rollers 32 and 33. Alternatively, an integral roller 35 with an annular groove 35a formed thereon as shown in Fig. 9 and a pair of rollers 36 with a V-shaped annular groove 36a formed thereon respectively as shown in Fig. 10 may be employed for the working apparatus 15.

Fig. 11 shows by way of a front view a modified example of a welding base material according to the present invention and Fig. 12 shows by way of a perspective view an elongated member which is produced using the base materials in Fig. 11.

As is readily apparent from Fig. 11, the base material 40 is formed in such a manner that both the end parts 41a of a plate 41 are swelled in the one direction to build thick walled portions 42. Four base materials 40 formed in that way are arranged in such a manner as illustrated in Fig. 12 while Vshaped welding grooves 43 are provided between the adjacent base materials 40, and welding operation is performed on each of the welding grooves 43 to construct a required elongated member 44.

Thus, by employing the method of producing the elongated member 44 as mentioned above it is possible to produce an elongated member such as main frame 45 for construction machine of which part is curved as illustrated in Fig. 13.

Figs. 14 to 16 show by way of sectional view the steps of producing the boss portions on the boom in Fig. 1.

First, a hole 47 is drilled on a plate 47, as shown in Fig. 14 and the hole 47 is then enlarged to build a thick walled portion 48 therearound, as shown in Fig. 15. Thereafter, a boss member 7 is fitted into the hole 47 and welding operation is performed along an annular welding groove 49 which is provided between the circumferential surface of the boss member 7 and the inner wall of the hole 47 on the plate 46, as shown in Fig. 16.

Fig. 17 shows by way of plan view a forming tool 50 for forming the circular thick walled portion 48 and Fig. 18 shows by way of a sectional view how forming operation is performed with the aid of the forming tool 50.

The forming tool 50 is designed in the tapered configuration and includes an enlarging member 51 with cutouts 51a fdrmed on the periphery thereof and upsetting members 52 each of which is fitted into the cutout 51a.

As the enlarging member 51 is displaced in the axial direction while it is rotated, the upsetting members 52 are rotated together with the enlarging member 51 while they rotate themselves in the cutouts 51a whereby enlarging operation is performed. As enlarging operation proceeds, the inner wall area of the hole 47 on the plate 46 which is fitted into the grooves 53 of the upsetting members 52 is subjected to upsetting until it becomes thick to the same thickness as the width of the grooves 53. At this moment it is preferably that the inner wall area of the hole 47 is locally preheated.

Fig. 19 shows by way of a side view a boom for a power shovel which has the circular cross-sectional shape. As is apparent from the drawing, the boom is constituted by three cylindrical pieces 56, 57 and 58 which are welded to one another to build cylindrical elongated member 55. Brackets 59 and 60 are welded to both the ends of the elongated member 55.

The elongated member 55 is produced by way of the steps of forming a thick walled portion 62 as shown in Fig. 20 by rolling the end part 61a of a pipe 61 to prepare a welding base material 63, bevelling the fore end of the thick walled portion 62 of the base material 63 as shown in Fig. 21, bring the thus beveled faces of the adjacent thick walled portions 62 in contact with one another to form an annular welding groove 64 and then performing welding operation around the welding groove 45 as represented by reference numeral 65.

Figs. 22 to 25 show by way of sectional view a concrete example of method of working the end part 61a of the pipe 61. Specifically, Fig. 22 illustrates a press forming method in which inward pressing is achieved with the use of a die 66, Fig. 23 does a press forming method in which outward pressing is achieved with the use of a die 67, Fig. 24 does a successive forming method in which upsetting is achieved with the use of rotational rolls 68 and Fig. 25 does a successive forming method in which roll forming is achieved with the use of a die 69. Obviously, required forming operation can be performed in accordance with any one of the above-described methods.

While the present invention has been described above with respect to preferred embodiments thereof, it should of course be understood that it should not be limited only to them but various changed or modification may be made in any acceptable manner without departure from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A welding base material comprising a member having substantially uniform wall thickness, wherein an end part of said member at which a welding groove is prepared is formed to a thick walled portion having the thickness greater than that of the rest of the member.

2. A welding base material as defined in claim 1, wherein said member is a plate.

3. A welding base material as defined in claim 1, wherein said member is a cylindrical member.

4. A method of forming a welding base material comprising the steps of: thrusting a roller against an end face at which a welding groove is prepared of a plate-shaped member having substantially uniform wall thickness; and displacing said roller relative to said plateshaped member so as to allow said end part of the member to be formed to a thick walled portion.

5. A method of forming a welding base material as defined in claim 4 further comprising the step of provisionally attaching dummy pieces whose material and thickness are determined same as those of said member to both sides of said end face of the member before said roller is thrusted against the end face of the member.

6. A method of forming a welding base material as defined in claim 4 further comprising the step of heating said end part of the member before said roller is thrusted against the end face of the member.

7. An apparatus for forming a welding base material comprising: holding means for holding a plate-shaped member on a platform of said apparatus in the upright standing state; and rolling means adapted to move along upper end face of said member to form a thick walled portion by rolling said upper end face of the member.

8. An apparatus for forming a welding base material as defined in claim 7 further comprising heating means adapted to move along said upper end face of the member held on the platform for heating the upper end face of the member.

9. An apparatus for forming a welding base material as defined in claim 7, wherein said holding means includes a stationary holding block fixedly mounted on the platform for holding one surface of the member a movable holding block disposed on the platform at the position located opposite to said stationary holding block so as to move toward and away from the stationary holding block, said movable holding block moving until it abuts against the other surface of the member, and a hydraulic cylinder for displacing the movable holding block toward the stationary holding block.

10. An apparatus for forming a welding base material as defined in claim 9, wherein said holding means further includes a pair of another movable holding blocks movably disposed on the platform for firmly holding both side end faces of the member and hydraulic cylinders for displacing said another movable holding blocks.

11. An apparatus for forming a welding base material as defined in claim 10, wherein each of said another movable holding blocks includes with a stopper plate adapted to abut against the side end face of the member.

12. An apparatus for forming a welding base material as defined in claim 11, wherein said stopper plate is adapted to move up and down and is normally urged upward under the effect of resilient force of a spring.

13. An apparatus for forming a welding base material as defined in claim 11, wherein said stopper plate is formed with a cutout at the upper end part thereof, said cutout being located opposite to the side end of the member.

14. An apparatus for forming a welding base material as defined in claim 7, wherein said rolling means includes a gate-shaped frame which is designed in such a manner as to stride over said upper end face of the member and move along the upper end face.

15. An apparatus for forming a welding base material as defined in claim 14, wherein said gate-shaped frame is equipped with a working roller adapted to come in pressure contact with said upper end face of the member to swell outward both upper end part of the member by deformation and a pair of thickness limiting rollers located in the proximity of both faces of the upper end part of the member for limiting an extent of swelling of both faces due to deformation of the upper end part of the member.

16. An apparatus for forming a welding base material as defined in claim 14, wherein said gate-shaped frame is equipped with a roller with an annular groove having an U-shaped cross-sectional contour formed thereon, the bottom surface of said annular groove serving to roll the upper end face of the member and both the side walls of the same serving to limit an extent of swelling of both faces of the upper end part of the member.

17. An apparatus for forming a welding base material as defined in claim 14, wherein said gate-shaped frame is equipped with a pair of rollers each of which has a V-shaped annular groove, the one side wall of said annular groove serving to roll a half of the upper end face of the member as seen in the direction of thickness of the latter and the other side wall of the same serving to limit an extent of swelling of the upper end part of the member, the side walls of both the annular grooves being combined to form an U-shaped groove.

18. An apparatus for forming a welding base material as defined in claim 8, wherein said heating means includes a gate-shaped frame which is designed in such a manner as to stride over the upper end face of the member and move along the upper end face.

19. An apparatus for forming a welding base material as defined in claim 18, wherein said gate-shaped frame is equipped with a pair of burners which are directed downward in the inclined state in such a manner that their flame is concentrated at the upper end part.