Claims:We claim:
1. A butt welding method for welding sheet metal plates having width even less than 15 mm, the butt welding method comprising:
arranging first metal sheet (01) and second metal sheet (02) with square butt edges, wherein a root gap (03) of 2 to 3 mm is provided in between the square butt edges of the first metal sheet (01) and the second metal sheet (02);
welding the root gap (03) provided between the first metal sheet (01) and the second metal sheet (02) from one side;
gauging the welded side; and
welding other side of the root gap (03) the first metal sheet (01) and the second metal sheet (02).

2. The method as claimed in claim 1, wherein the welding is full penetration weld with preheating and post heating.

3. The method as claimed in claim 1, wherein the welding is full penetration weld without preheating and post heating.

4. The method as claimed in claim 1, wherein the welding is selected from any fusion welding process especially Shielded / Manual Metal Arc Welding, Gas Metal Arc Welding or MIG / MAG welding.

5. The method as claimed in claim 1, wherein the gauging is back gauging which is done by grinding mechanism.

6. The method as claimed in claim 1, wherein the first metal sheet (01) and the second metal sheet (02) have thickness in range of 5 to 8 mm.

7. The method as claimed in claim 1, wherein the full penetration welds are made with square butt edge preparation.
8. The method as claimed in claim 1, wherein arc of welding is short, medium, and long arc depends upon welding parameters.
9. The method as claimed in claim 1, wherein the welding of the sides of the root gap (03) penetrates the root gap and meets with the welding of the other side.
10. The method as claimed in claim 1, wherein the method is used to make the full penetration weld by any filler wire / welding consumable suitable to the material.
11. The method as claimed in claim 1, wherein the method is used to make the full penetration weld through manual, mechanized, semi – automated, robotic and / or automated welding modes.
12. The method as claimed in claim 1, wherein the method is used to make the full penetration weld with suitable size of filler wire / electrode.
13. The method as claimed in claim 1, wherein the method is used for welding of similar dissimilar weld joints.
14. The method as claimed in claim 1, wherein the welding of the square butt joints is by SMAW process using 3.15 mm dia and E 8018 B2 electrodes with Pre heat temperature 120° C and voltage in range 16-18 V and arc length is short.
, Description:METHOD FOR BUTT WELDING OF LOW THICK PLATES WITHOUT EDGE PREPARATION FOR FULL PENETRATION WELDS TO MEET ASME CODE REQUIREMENTS
FIELD OF INVENTION:
[001] The present subject matter described herein, relates to a method for butt welding of 5 to 8 mm thick plates without edge preparation for full penetration welds to meet ASME code requirement. This present subject matter relates to the process development for achieving full penetration welds with square butt edge preparation in 5 to 8 mm thick plates by fusion welding processes (Shielded / Manual metal Arc Welding (SMAW / MMAW), Gas Metal Arc Welding (GMAW or MIG / MAG) to fabricate components as per ASME or equivalent code, etc.
[002] The present subject matter serves the purpose of ensuring flawless joints in fusion welding of plates 5 to 8 mm with square butt edge preparation for increased productivity.
[003] This present subject matter related to the process development for joining 5 to 8 mm thick plates with a different innovative method of welding to avoid edge preparation as well as to make a defect free weld as per ASME code or its equivalents’ requirements.
BACKGROUND AND PRIOR ART:
[004] Normally, to ensure full penetration welds in 5 to 8 mm thick plates, single V or J type edge preparation will be done prior to weld. At the time of fit up, 2 to 3 mm root gap will be provided between the joining surfaces as shown in Figure 01. After that the weld is done from single side to ensure full penetration welds to meet the code of construction or acceptance criteria. The weld is subjected to the non - destructive inspection methods depending upon the acceptance criteria / procedure requirements. The same method cannot be used in all types of requirements as detailed below.
[005] Insufficient availability of parent material width. To make a single V edge preparation we need a minimum of 15 mm width on a single side.
[006] J groove weld will not result in full penetration welds always.
[007] ASME and equivalent codes are not permitting any type of penetration related flaws in the weld joints.
[008] Indian Patent application publication 2796/DELNP/2012 titled “WORK PIECE POSITIONING DEVICE AND METHOD, AND A WORK PIECE POSITIONING DEVICE FOR BUTT WELDING” relates to a butt welding of plate-like work pieces, improper butting of the work pieces partially creates a weak welding area. The work pieces therefore need to be properly butted to each other in a stage prior to the butt welding. A generally-known method uses a pusher to press work pieces from behind towards a stopper (including the case when one of the work pieces, which is fixed in a predetermined position, serves as a stopper) and thus carries out accurate positioning of the work pieces. This method has not many problems if the work pieces are substantially rectangular in shape. On the other hand, if the edges to be butted and the opposite edges in the work pieces extend slantwise relative to a pressing direction or if they curve, pressing the opposite edges with the pusher causes the problem that a component force acts upon a pressing point, which leads to unsuccessful pressing.
[009] To solve this problem, the work piece positioning device disclosed in Indian Patent Application provided with an actuator driven reciprocating member under a receiving board on which a work piece is placed. A suction device is supported by the reciprocating member so as to be movable in a vertical direction and also tiltable. The suction device sucks the lower face of the work piece placed on the receiving board.
[0010] The reciprocating member is displaced by the actuator and made to press the work piece towards a stopper. According to a positioning device like this one, even if the opposite edges of the work pieces extend at a slant or if they curve, the pressing can be carried out by sucking the lower face of the work piece by using the suction device. Accordingly, the Indian Patent Publication does solve technical problem of the present invention, as it is about a positioning device for work pieces for butt joining.
[0011] PCT Patent publication WO2010046937A1 titled “Method for butt welding sheet metal plates, and welding machine for the application of this method” discloses a butt welding method for sheet metal plates comprises the following steps: providing a first and a second sheet metal plate edge (Pl, P2) arranged to butt against each other in such a way that a gap (G) is left between them; and forming a through weld between the first and second sheet metal plate edges in the gap. The formation of the through weld comprises the following operations: forming a first weld bead (DW) on one side of the plate edges by continuous wire arc welding using a pair of wire electrodes (21a, 21b) converging towards the gap and extending transversely with respect to the direction of extension of the gap, this first weld bead penetrating into the gap by an amount equal to a fraction of the thickness of the plate edges; and forming a, second weld bead (UW) on the opposite side of the plate edges, using continuous wire arc welding, this second weld bead penetrating into the gap until it meets the first weld bead.
[0012] The above WIPO patent publication is related to continuous wire welding only. Though, the patent talks about sheet metal plates which is limited to 3.15 mm thick only and it does not specify about the thickness of the plate.
[0013] United States Patent publication US 8,097,826 B2 dated Jan. 17, 2012 and titled, “PENETRATION ENHANCING FLUX FORMULATION FOR TUNGSTEN INERT GAS (TIG) WELDING OF AUSTENITIC STAINLESS STEEL AND ITS APPLICATION” discloses a penetration Enhancing Activating Flux (PEAF) in paste form for autogenous TIG Welding of austenitic stainless steels adapted for ready application With a brush on top Weld surface prior to conducting autogenous TIG Welding to favor single Weld pass, of austenitic stainless steels of AlSl 304LN and AlSl 316LN varieties With Weld bead penetration up to a section thickness of 12 mm. Importantly, the (PEAF) paste based TIG Welding of the invention achieves an increase in Weld bead penetration of about 300% over the conventional TIG process Without activating ?ux. The PEAF paste based TIG Welding also favors higher productivity and high quality apart from being cost-effective due to less requirements of consumables and controlled heat input to arrest distortion, making it widely acceptable for variety of industrial applications for Welding of austenitic stainless steel.
[0014] The above patent is related to penetration enhancing flux which is not at all related to the present invention and technical problem of the present invention.
[0015] In the current practice, full penetration welds in 5 to 8 mm thick plates (item no. 01 and 02) could be achieved by single V or J type edge preparation and welding will be carried out from one side with sufficient root gap as shown in Fig. 1. At the time of fit up, 2 to 3 mm root gap will be provided between the joining surfaces. After that the weld will be done from single side to ensure full penetration welds to meet the code of construction or acceptance criteria. The welds will be subjected to the non - destructive inspection methods depending upon the acceptance criteria / procedure requirements. The same method cannot be used in all types of requirements as detailed below. Therefore, these are technical problems:
[0016] Insufficient availability of parent material width. To make a single V edge preparation we need a minimum of 15 mm width on a single side.
[0017] J groove weld will not result in full penetration welds always.
[0018] ASME and equivalent codes are not permitting any type of penetration related flaws in the weld joints.
[0019] Hence there is a need to improve butt welding for fast and efficient welding of two parts of 3 to 8 mm thick plates.
OBJECTS OF THE INVENTION:
[0020] The principal objective of the present invention is to provide method for butt welding of 5 to 8 mm thick plates having width even less than 15 mm, without edge preparation for full penetration welds to meet ASME code or its equivalents’ requirement.
[0021] Another object of the present subject matter is to develop joining method for achieving full penetration welds with square butt edge preparation in 5 to 8 mm thick plates by fusion welding processes (Shielded / Manual metal Arc Welding (SMAW / MMAW), Gas Metal Arc Welding (GMAW or MIG / MAG).
[0022] Another object of the present subject matter is to improve upon the productivity using the modified process.
[0023] Yet another object of the present subject matter is to avoid V or J groove edge preparation in the metal sheet before welding process.
SUMMARY OF THE INVENTION:
[0024] The subject matter disclosed herein relates to a method for butt welding of 5 to 8 mm thick plates having width even less than 15 mm, without edge preparation for full penetration welds to meet ASME code requirement has been developed successfully. By using the present method, full penetration welds with square butt edge preparation in 5 to 8 mm thick plates could be achieved by fusion welding processes (Shielded / Manual metal Arc Welding (SMAW / MMAW), Gas Metal Arc Welding (GMAW or MIG / MAG) to fabricate components as per ASME or equivalent code, etc.
[0025] In order to further understand the characteristics and technical contents of the present subject matter, a description relating thereto will be made with reference to the accompanying drawings. However, the drawings are illustrative only but not used to limit scope of the present subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments. The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0027] Fig. 1 illustrates typical edge preparations for sheet metal plates, the plates to be joined by welding;
[0028] Fig. 2 illustrates square butt edge preparation for metal sheet 01 and metal sheet 02 to make the weld by the present method, in accordance with the present subject matter; and
[0029] Fig. 3 illustrates macrographs of the weld without defects / discontinuity.
[0030] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
[0031] The subject matter disclosed herein relates to a method of square butt welding of 5 to 8 mm thick plates having width even less than 15 mm, without edge preparation for full penetration welds to meet ASME code requirement has been developed successfully. By using the present method, full penetration welds with square butt edge preparation in 5 to 8 mm thick plates could be achieved by fusion welding processes (Shielded / Manual metal Arc Welding (SMAW / MMAW), Gas Metal Arc Welding (GMAW or MIG / MAG) to fabricate components as per ASME or equivalent code, etc.
[0032] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various arrangements that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.
[0033] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0034] Referring to Fig. 2, a method is shown for full penetration welds with square butt edge preparation between plates. The metal sheets 01 and 02 have thickness in range 5 mm to 8 mm which are to be welded are prepared for square butt edge. The metal sheets 01, 02 are prepared for square butt edge. There is no edge preparation for welding. After preparation of the square butt edge, fit up of plate assembly is taken up after cleaning the joining surfaces with a root gap 03 of 2 to 3 mm. Once fitment of the metal sheets 01 and 02 is complete with a root gap 03, welding is done from one side with appropriate parameters viz. welding current, voltage, welding speed, etc. On completion of weld from one side, the metal sheets welded with each other from one side is reversed and back gouging is done by grinding or any other operation which is known. Further, a dye / liquid penetrate testing / inspection on the ground areas is carried out to ensure that no flaw is present. After inspection, welding is carried out from the other side. On completion of weld, slag, spatter, etc. if any present is cleaned. At last, visual inspection is carried out on the weld. This is followed by magnetic particle inspection of the weld to ensure weld soundness.
[0035] Typical welding parameters are shown in Table 01.
DESCRIPTION VALUE
Process SMAW
Type of current DCEP
Electrode specification E 8018 B2
Size Dia 3.15
Voltage 16 – 18 V
Current 120 – 125 A
Preheat temp 120° C
Arc length Short arc
Joint type Square butt
Root Gap 2 to 3 mm

[0036] The experimental work carried out in the trial weld to achieve full penetration welds in Gr. 12 material is briefed below.
[0037] Grade 12 plates have been taken up and welded with square butt joints by SMAW process using 3.15 mm dia. E 8018 B2 electrodes. Pre heat temperature 120° C.
[0038] Plates were tack welded with a root gap of 2 mm.
[0039] After welding from one side, back gouging of the weld was done by grinding.
[0040] Carried out Dye penetrant test to remove defects if any, in the root area.
[0041] Welded from other side also.
[0042] Used different weld parameters.
[0043] Carried out PWHT at 655 ± 15° C with 30 min. soaking time in furnace.
[0044] MPI of joints was carried out WRI
[0045] Macro analysis of the joints was carried out in WRI (Refer Figure 03)
[0046] The present subject matter describes a method for butt welding of 5 to 8 mm thick metal sheets/plates without edge preparation for full penetration welds to meet ASME code or its equivalents’ requirement.
[0047] In the present method, the development is unique for butt welding of 5 to 8 mm thick plates without edge preparation for full penetration welds of metal sheets no. 01 & 02 as shown in Figure 02. The present method can be used to make full penetration welds with square butt edge preparation. The present method can be used make full penetration welds with a root gap of 2 to 3 mm. The present method can be used to make the full penetration weld by any fusion welding process especially Shielded / Manual Metal Arc Welding, Gas Metal Arc Welding or MIG / MAG welding. The present method may be used to make the full penetration weld by any filler wire / welding consumable suitable to the material. The present method can be used to make the full penetration weld with or without preheating and or post heating.
[0048] The present method can be used to make the full penetration weld by selecting suitable welding parameters viz., suitable welding voltage, current and travel speed, etc. The present method can be used to make the full penetration weld through manual, mechanized, semi – automated, robotic and/or automated welding modes. The present method can be used to make the full penetration welds with short/medium/long arc depending upon the welding parameters. The present method can be used to make the full penetration weld with suitable size of filler wire / electrode. The present method can be used for welding of similar dissimilar weld joints. The present method can be used for any type of material in the thickness range of 5 mm to 8 mm. The present method can be used to make full penetration welds to meet the requirements of ASME code or equivalent code.
[0049] Advantages of the Invention
[0050] The present method reduces the turnaround time of the butt welding which was wasted in the edge preparation. The present method provides a square butt welding method without any edge preparation. Therefore, the present method provides square butt joints with high rate and better quality.
[0051] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.