CA2435627A1 - A contact tip for gas-metal-arc-welding - Google Patents
A contact tip for gas-metal-arc-welding Download PDFInfo
- Publication number
- CA2435627A1 CA2435627A1 CA 2435627 CA2435627A CA2435627A1 CA 2435627 A1 CA2435627 A1 CA 2435627A1 CA 2435627 CA2435627 CA 2435627 CA 2435627 A CA2435627 A CA 2435627A CA 2435627 A1 CA2435627 A1 CA 2435627A1
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- CA
- Canada
- Prior art keywords
- tip
- aperture
- section
- wire feed
- contact
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/12—Automatic feeding or moving of electrodes or work for spot or seam welding or cutting
- B23K9/133—Means for feeding electrodes, e.g. drums, rolls, motors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/24—Features related to electrodes
- B23K9/26—Accessories for electrodes, e.g. ignition tips
Abstract
The contact tip is used for electric arc welding in a protective gas medium (MIG-MAG
welding) or under a layer of flux, feeding the wire electrode from the wire-feeding device through the tip torch to the weld zone, simultaneously conducting current to the wire. The aperture comprises sectors with triangular and circular cross section or the aperture shape can be helical with a triangular cross section, and part of its sector with a triangular cross section can be fabricated as a separate bush. The wire electrode contacts the walls and arms of the angles of the triangular aperture and it has minimal elastic energy. The shape of the wire feed aperture provides simultaneous increase of the contact areas and tip/wire contact pressure together with high passability, regardless of the tip length and the presence of cumulative deposit of dirt and extraneous matter from the welding wire or electrode surface.
welding) or under a layer of flux, feeding the wire electrode from the wire-feeding device through the tip torch to the weld zone, simultaneously conducting current to the wire. The aperture comprises sectors with triangular and circular cross section or the aperture shape can be helical with a triangular cross section, and part of its sector with a triangular cross section can be fabricated as a separate bush. The wire electrode contacts the walls and arms of the angles of the triangular aperture and it has minimal elastic energy. The shape of the wire feed aperture provides simultaneous increase of the contact areas and tip/wire contact pressure together with high passability, regardless of the tip length and the presence of cumulative deposit of dirt and extraneous matter from the welding wire or electrode surface.
Description
Description BACKGROUND OF THE INVENTION
1. Field of the Invention This invention relates to contact tip for gas~metal arc welding. The tip is used for electric-arc welding by means of continuous metal wire electrode in a protective gas medium (MIG-MAG-welding) or hidden arc welding.
1. Field of the Invention This invention relates to contact tip for gas~metal arc welding. The tip is used for electric-arc welding by means of continuous metal wire electrode in a protective gas medium (MIG-MAG-welding) or hidden arc welding.
2. Description of the Prior Art A contact tip for gas-metal arc welding is a tubular body having a central wire feed aperture which serves for feeding welding wire from wire-feeding device through a welding torch and into the weld zone. In addition to feeding the welding wire, the contact tip also transfer electric current to the welding wire electrode. Wire goes out of the contact tip outlet and forms a short and charged front length, and an electric arc is formed between the charged end of the wire electrode and the oppositely charged work-piece. The arc melts the wire electrode, thus continuously providing melted metal to form a weld puddle. Welding machines and apparatuses also comprise a gas nozzle, wherein the nozzle and the contact tip for gas~metal arc welding are coaxial.
The nozzle blows inert or active gas over the weld puddle, separating atmospheric air from the weld puddle. This avoids unwanted reactions of the molten material with the surrounding air. Thus, one can obtain clean weld of good quality. In most welding apparatuses, the welding wire electrode is wound on a spool, and it is unwound by the welding wire feeder. The wire electrode is automatically fed off the spool and into the contact tip welding torch. The wire electrode is unwound off the spool, having a specific cast which is arcuate in nature, and it is elastically straightened in the wire feed aperture and is pressed to the wire feed aperture walls. This effect is favo ~eable for the current transfer, since it maintains good electric conductivity between the welding wire electrode and the surface of the wire feed aperture. Wire must move smoothly through the tip aperture without jerking, thus providing exact and high performance welding. The wire feed aperture of the contact tip for gas-metal arc welding is made with dimension tolerance between the wire electrode and the wire feed aperture.
However, the increase of the wire/aperture gap over a definite limit yields poor contact between the wire electrode and the surface of the wire feed aperture, deteriorating the welding process. The presence of debris carried by the surface of the wire electrode and introduced in the wire feed aperture or formed in the wire feed aperture as a result of electric erosion increases the risk of choking the wire feed aperture, especially when the gap is small. These and a number of other requirements to the contact tip for gas-metal arc welding, contradicting to each other, explain the existence of different constructional solutions of the contact tip. Yet, each of them has specific disadvantages.
The most popular contact tip for ga~metal arc welding is a tubular body with a cylindrical central wire feed aperture. A disadvantage of such a tip is its short term of exploitation, due to wear caused by intensive abrasion or electrical erosion. This is so, since the current loads are too great (welding current has power of 100-800 A). Moreover, current is transferred by means of a three-point contact between the welding wire electrode and the contact tip, only (contact at the back receiving end of the wire feed aperture, contact in the aperture middle and at contact the aperture front contact end), and the contact areas are too small. Besides, pressure along the contact surfaces is insignificant and of variable magnitude. The trend of one to decrease the wire/aperture gap in order to improve the contact does not increase the contact area, but worsens the passability of the wire feed aperture and increases the risk of blockage of the wire electrode within the aperture.
Besides, since the wire feed aperture has a circular cross section, the wire electrode rotates within the aperture during welding, which impedes the exact wire feed towards the weld puddle. Due the wire electrode rotation and electric erosion, contact areas change in time their sizes and the process of current transfer becomes norrsteady. As a result, the welding arc becomes instable which yielding weld of poor quality. The outlined norrsteadiness of the current transfer also yields generation of sporadic liquid metal bursts, which fall into and stick to the weld and to the area surrounding it. Thus, the weld quality worsens additionally. On the other hand, bursts being regularly expelled from the weld zone as miniature droplets, bind and build up to the contact end of the contact tip. Thus, they yield additional thermal loads, tip oxidation and burn-through etc. These effects decrease the exploitation term of the contact tip for gas~metal arc welding. Burst can sometimes enter the zone of the wire feed aperture outlet, disturbing motion of the wire electrode and yielding instability of wire electrode transport, poor weld initiation or tip failure.
Other constructional solutions of a contact tip for gas-metal arc welding are also known - see, for instance patent BG 63039 B 1, where the cross section of the tip wire feed aperture is not circular and the cross section boundary is mt a smooth line, but it has at least one kink (one angle).
However, these solutions manage to eliminate some of the outlined functional disadvantages of a contact tip for gas-metal arc welding with a circular cross section, and the positive effects are result of the following reasons: the rotation of the wire electrode in the tip wire feed aperture is significantly suppressed, since wire electrode occupies one angle of the aperture cross section and it is thus fixed (i.e. the arc is stabilized); the number of contact points between the wire electrode and the walls of the wire feed aperture, at the aperture back receiving end, in its middle section and at the aperture front contact end, is doubled, since two-point contact is attained on the angle arms, while the contact in a tip with a circular cross section takes place at one point; contact forces acting between the wire electrode and the aperture become larger. Moreover, considering tips with triangular wire feed apertures, the welding wire electrode contacts the tip along a line, lying in one of the planes of the tip prismatic wire feed aperture. In addition, such contact is established at three more points, lying in the other two planes of the prismatic wire feed aperture - at the tip back receiving end, in its middle section and at the tip front contact end. The problem of these contact tips for ga~metal arc welding is how to find the gap between the wire electrode and the tip aperture.
Considering a contact tip for gas-metal arc welding whose cross section is triangular, the wire electrode should have a diameter, smaller than that of the circle, inscribed in the triangle. Thus, wire could pass through the tip cross section. Yet, the assumption of the difference between the diameter of the circle inscribed in the aperture triangular cross section and the diameter of the wire electrode as a measure of looseness is not appropriate and yields unreliable results.
This is so, since the wire electrode, passing through the wire feed aperture, occupies one of the angles of the triangle, and its elastic pre-stressing relaxes to a certain extent. Hence, one should know the optimal practical parameters of the triangular cross section, thus providing optimal conditions of current transfer and norrdisturbed and smooth motion of the wire electrode through the triangular wire feed aperture.
Other constructional solutions of contact tips for gas-metal arc welding (CT) are also known - see patents BG 60184 and CA 1247707, where the axis of the wire feed aperture is a helix. Moreover, a linear contact between the wire electrode and the tip wire feed aperture is attained along a helix.
This contact is much better than the three-point contact attained in a tip with a circular cross section.
It also is comparable to the contact in tips with noircircular cross section.
Besides (as in a contact tip with a norrcircular aperture) contact pressure between the wire electrode and the wire feed aperture is higher than pressure in tips with a circular wire feed aperture, since the wire e~ctrode is forced to change continuously and elastically its curvature along the whole length of the contact tip.
A disadvantage of such contact tip for gas-metal arc welding (patent CA1247707) relates to the specificity that the helical passage for wire motion is laterally open towards the tip outside surface, forcing the helical tip aperture to make at least one full rotation.
Otherwise, the wire electrode would go out of the contact tip and it could not be forced to follow the contact tip axis. The specificity that the wire electrode passage is open yields two more problems, which concern metal spatter binding and building up to the front end of the laterally open passage and the exact direction of the wire electrode towards the weld zone. This implies additional mounting of an insert at the front contact end of the tip, and this complication, together with the non-technological construction, is a reason for the tip high cost.
Considering a number of cases of welding, one should use contact tip for gas metal arc welding with significantly increased length. However, the increase of the tip length yields increase of friction during wire electrode motion, which hampers wire electrode feeding and sometimes even blocks the wire electrode in the wire feed aperture. Constructional solutions are known, where this problem is solved by fabricating the contact tip as a cylindrical tube with circular cross section of the wire feed aperture. Moreover, the tip has smaller outside and inside diameters at its front contact sector, as compared to the outside and inside diameters of the rest part of the tip, i.e.
the tip is a monolithic body consisting of two tubular sectors with different outside and inside diameters. The sector with smaller outside and inside diameters has a length, approximately equal to the length of a regular contact tip for gas-metal arc welding, and it is located at the front contact end of the tip, i.e. in the area where the wire electrode projects out of the contact tip and is fed to the weld. The electric contact between the contact tip and the wire electrode is achieved in this sector, which is comparably shorter and the wire feed aperture has a smaller diameter. The rest part of the tip has larger outside and inside diameters, so that the smooth motion of the wire electrode would not be disturbed. However, these tips have the disadvantages inherent to all contact tips for gas-metal arc welding with a circular aperture, considered so far: limited three-point tip/wire contact, fast abrasion and electric erosion and short term of exploitation.
Some solutions, considering the external design of a contact tip for gas-metal arc welding are known, where a groove is fabricated on the tip external cylindrical surface.
Yet, the groove function is not related to the welding process, but the groove is cut for one to hold the tip by a wrench for mounting it to and/or dismounting it from the torch. Besides, groove cut is an additional operation which is not part of the basic technologies of fabricating the tip a~pper tubular body (pressing, drawing, mechanical drilling etc.) and it increases the tip total cost.
SUMMARY OF THE INVENTION
The aim of the present invention is to provide a new construction of a contact tip for gas-metal-arc-welding, which would significantly eliminate the disadvantages of the contact tips discussed so far, increasing the contact areas and contact stresses which occur between the wire electrode and the tip wire feed aperture, but without decreasing wire electrode passability. At the same time, the design proposed would limit the rotation of the wire electrode within the wire feed aperture. The profits of the invention are as follows: significant improvement of current transfer and decrease of the generation of melted metal spatters; limitation of the possibility of blockage of the wire electrode within the wire feed aperture as a result of large friction stresses (for contact tips with large length) or as a result of the small gap between the wire electrode and the wire feed aperture; providing great variety of combinations of contact areas and contact stresses; thus guaranteeing effective conditions of current transfer for a wide range of lengths of contact tips for gas-meta~arc-welding, the range comprising very short and very long contact tips. Besides, the tip construction is technologically appropriate for smooth tip fabrication.
The aim of the invention is attained by designing a contact tip for gas-metal-arc-welding, fabricated from copper, copper alloy or powder metallurgy (PM) sintered material having high electrical and thermal conductivity. The contact tip is for use in a welding torch and it serves to feed the wire electrode to the weld and to pass the electric charge from the torch to the wire electrode. The contact tip comprises a tubular body with a central passable wire feed aperture whose axis is rectilinear. The aperture has a back receiving end on the side where the wire electrode is fed to the contact tip aperture through a specially shaped inlet cone. The aperture also has a front contact end on the side where the wire electrode projects from the tip, being directed to the weld.
Considering an aspect of the invention, the wire feed aperture of the contact tip does not have a uniform cross section along its whole length, but it has at least one sector, which starts at the tip front contact end and its cross section is triangular while its length is smaller than the whole aperture length The rest of the wire feed aperture has a circular cross section with a diame ter, larger than the s diameters of the circle inscribed in the cross section of any sector of the wire feed aperture which has triangular cross section.
Considering one of the preferable technological solutions of the present invention, the wire feed aperture of the contact tip comprises three sectors, two of which have a triangular cross section and are located at both tip ends. The third sector occupies the rest middle part of the wire feed aperture and has a circular cross section, while its diameter is larger than the diameters of the circles inscribed in the triangular cross sections of the above said two aperture sectors.
Considering another preferable technological solution of the present invention, the wire feed aperture of the contact tip comprises four sectors. Two of them have triangular cross section, and the first one is located at the tip front contact end while the second one is located in the middle part of the contact tip. The wire feed aperture between these two sectors, together with the aperture of the tip back receiving end, have a circular cross section with a diameter larger than the diameters of the circles inscribed in the triangular cross sections of the above said two aperture sectors.
Considering a preferable variant of the cottact tip, related to tips that have two sectors with triangular wire feed apertures, the said sectors have identical cross sections which are equilateral triangles. The said sectors are rotated with respect to each other around the aperture longitudinal axis at an angle of 60°.
As for another aspect of the present invention, the tip outside surface, enveloping the said tip sectors whose aperture cross section is triangular, is shaped as a hexagonal prism with three plane and three curved walls. Besides, all prism walls are parallel to the tip longitudinal axis. Moreover, the plane walls of the prism are parallel and equidistant to the corresponding inside walls of the triangular wire feed aperture of the said sectors. As for the subsequent tip sectors whose aperture has a circular cross section, the outside tip surface enveloping them is cylindrical.
As for another aspect of the present invention and considering the tip sector located at the tip front contact end and having a triangular cross section, the ratio between the diameter of the circle inscribed in the triangular cross section of the said tip sector and the diameter of the wire electrode is 1.15 - 1.25.
As for another aspect of the present invention, the tip sector located at the tip front contact end has a triangular aperture, and the aperture surface is helical, while the aperture longitudinal axis coincides with the longitudinal axis of the tip. Besides, the center of the circle inscribed in the triangular cross section of the said sector is the cross point of the bisectrixes of the triangle, and the said circle center does not lie on the tip axis.
In a preferable version of the present invention related to contact tips for gas-metal~arc-welding where the surface of the wire feed aperture is helical, the cross section of the said wire feed aperture is an equilateral triangle, and the bisectrix of one of the angles of the said triangle crosses the axis of the contact tip at a point, whose distance to the vertex of the said angle is smaller than the diameter of the wire electrode.
Considering a preferable version of the present invention related to contact tips for gas-metal-arc-welding where the surface of the wire feed aperture is helical and the cross section of the said aperture is triangular, the bisectrix of one of the angles of the said triangular cross section crosses the axis of the contact tip at a point whose distance to the vertex of the said angle is smaller than the radius of the wire electrode divided by the sinus of half of the said angle.
Considering a preferable version of the present invention related to contact tips for gas-metal-arc-welding where the wire feed aperture has a helical surface and the cross section of the wire feed aperture is triangular, one of the sides of the said triangular cross section is curvilinear and convex while the other two sides of the said triangular cross section are rectilinear. The curvilinear side of the said triangular cross section is an arc of a circle, while the diameter of the said circle is larger than the diameter of the wire electrode. The said arc is equidistant to a circle having a diameter equal to the diameter of the wire electrode, and the said circle tangents the arms of the angle concluded by the said rectilinear sides of the aperture triangular cross section.
As for another aspect of the present invention, a sector of the wire feed aperture being located at the tip front contact end and having a triangular cross section, is fabricated as a separate insert. The said insert is pressed in an aperture bored through the tip front contact end or the said insert is threaded to the tip front contact end.
As for another aspect of the present invention, a method of fabricating a contact tip for gas-metal-arc-welding is proposed. The tip has sectors with triangular wire feed aperture while the outside surface enveloping the said sectors is shaped as a hexagonal prism. Using the method of tip fabrication proposed, processes of plastic forming - forging or rolling are applied. Furthermore, the said method comprises an initial fabrication stage, in which a cylindrical tubular pre-form of copper or copper alloy, with a passable aperture of circular cross section, is placed in a matrix for forging or in a rolling stand for rolling. Then, a second stage of plastic forming follows, resulting in the plastic forming of the tubular pre-form or of a sector of the tubular pre-form into a body, whose deformed section is a tube with a hexagonal outside enveloping surface and which has a passable wire feed aperture with a triangular cross section. According to the method proposed, the said outside enveloping hexagonal surface and the said wire feed aperture with a triangular cross section are obtained simultaneously as a result of the power impact of the forming instrument. The power impact is applied on the outside surface of the pre- form, only, and the power impact is directed perpendicularly to the pre-form axis. Besides, the instrument shape-forming faces which contact the pre-form and exercise power impact on it, conclude with each other angles which are equal to the angles of the cross section of the said triangular aperture .
BRIEF DESCRIPTION OF THE DRAWINGS
The enclosed figures provide a better clarification of the essence of the present invention The figures illustrate the following characteristic features of the contact tip for gas-metal-arc-welding:
Fig. 1 shows a longitudinal section of the contact tip together with the wire electrode inserted in it.
Fig. 2 shows a longitudinal section of a contact tip with two-sector wire feed aperture.
Fig. 3 shows an axonometric view of the position of the wire electrode in a wire feed aperture with a triangular cross section.
Fig. 4 shows a longitudinal section of a contact tip with a three-sector wire feed aperture.
Fig. 5 shows a cross section c - c of the contact tip in Fig. 4 with triangular wire feed apertures, wherein the aperture cross sections are rotated with respect to each other at an angle of 60° around the tip longitudinal axis.
Fig. 6 shows an axonometric view of a contact tip, wherein part of its outside enveloping surface is shaped as a hexagonal prism.
Fig. 7 shows an axonometric view of a four-sector contact tip with a wire feed aperture as shown in Fig. 5.
Fig. 8 shows an axonometric view of a contact tip with a helical aperture which has a triangular cross section.
Fig. 9 shows a cross section of a contact tip with a helical wire feed aperture with a triangular cross section.
Fig. 10 shows a cross section of a contact tip with a helical wire feed aperture, whose triangular cross section has one convex aro-shaped side.
Fig. I 1 shows a longitudinal section of a contact tip with a hammered-in insert, wherein the insert has an aperture with a triangular cross section.
Fig. 12 shows a longitudinal section of a contact tip with a threaded insert, wherein the insert has an aperture with a triangular cross section.
Fig. 13 shows a cross section of a stamp (matrix) for the fabrication of a contact tip whose aperture has a triangular cross section and whose outside enveloping surface is hexagonal.
Fig. 14 shows a rolling stand for the fabrication of a contact tip whose aperture has a triangular cross section and whose outside enveloping surface is hexagonal.
DETAILED DESCRIPTION OF THE INVENTION
Considering the enclosed figures 1 -14, the part specified as position 1 generally maps a contact tip for use in a welding torch which is not shown in the figure.
As seen in Fig. 1, the contact tip 1 is a tubulax body with a central passable wire feed aperture 2 and the aperture axis is rectilinear. The aperture 2 has a back receiving end Ib on the side where the wire electrode 4 is fed in the aperture 2 of the contact tip 1 through a specially shaped inlet cone 5. The wire feed aperture 2 also has a front contact end if on the side where the wire electrode 4 projects from the contact tip 1 and is directed to the weld 3. The contact tip is fixed to the element 6 (diffuser) through its receiving end lb. The contact tip through its receiving end lb. is fixed either to the element 6 (diffixser) of the welding torch or to the carrier of the welding apparatus. The wire electrode 4 which has a natural curvature passes through the wire feed aperture 2 of the contact tip I, deforms elastically and is thus pressed to the walls of the aperture 2 at points 7.
Fig. 2 shows the contact tip I, wherein the wire feed aperture 2 does not have a uniform cross section along its whole length, but sector A of the wire feed aperture 2 starts from the front contact end of the contact tip I and has a triangular cross section 2a. A second sector B is shaped at the back receiving end of the contact tip I and it has a circular cross section 2b. T'he second sector B
starts from the receiving inlet cone 5 and stretches to the first sector A.
The diameter of the aperture of the second sector B is larger than the diameter of the circle inscribed in the triangular cross section 2a of the first sector A of the wire feed aperture 2. As for the contact tip under consideration the effective contact realizing current transfer from the tip I to the wire electrode 4 occurs in sector A of the wire feed aperture. The aperture sector A has a triangular cross section 2a and the wireJaperture gap is smaller. The character of the contact is shown in Fig. 3.
The position of the wire electrode 4 in the prismatic triangular sector A of the wire feed aperture 2, shown in Fig. 3, is the most stable one as compared to all possible positions of the wire electrode.
This is so, since minimum of the potential energy of elastic stressing of the wire electrode 4 is attained in this wire position. The wire electrode 4 realizes linear contact 10 with the wall 8a of the triangular prismatic sector A of the wire feed aperture 2. 'The wire electrode 4 additionally contacts the other two sides of the triangular prismatic sector A at three more points (at two points 7b located at both ends of wall 8b and at one point 7c located in the middle of wall 8c). While current transfer in a two-sector contact tip (Fig.2) is realized in sector A which has a triangular cross section, as outlined above, sector B of the contact tip I with a circular cross section of the wire feed aperture 2 has a function of elongating the contact tip I to the length needed. This is done in accordance with the specific requirements of the welding machinery and technology employed, without increasing the wire resistance to push out of the aperture. Thus, one can attain balance between the optimal conditions of current transfer (characterized by appropriate gaps, increased contact areas and pressure and stable angular fixing) and good passability of the wire electrode, especially in contact tips with larger length. As a result, the welding are is stable, the amount of spatter is significantly smaller, the accuracy of directing the wire electrode to the weld is higher, the probability of wire electrode blockage within the wire feed aperture is decreased and the exploitation term of the contact tip is increased. As a whole, the weld is of high quality.
Fig. 4 shows a contact tip I whose wire feed aperture 2 has three sectors - A~
, Az and B. Sectors A~
and Az are located at the tip front (contact) and at its back (receiving) end (just at the inlet cone 5).
Those sectors have triangular cross sections 2a~ and 2a2. A third sector B is located between sectors A~ and AQ, in the tip middle section, and sector B has a circular cross section 2b whose diameter is io larger than the diameter of the circles inscribed in the triangular cross sections 2a~ and 2a2 of sectors A~ and A2. Such a design of a contact tip for gas-meta~arc-welding is preferable when the specific conditions of welding require that the tip length be significantly larger than the length of an ordinary and most common tip. Hence, it is useful for one to divide the triangular sector of the wire feed aperture into two parts (i.e. into the two sectors ~ and AQ discussed above, as shown in Fig. 4).
They are located at both tip ends, since wire fixing along a larger length yields stronger resstance to rotation of the wire electrode. Thus, one can attain the necessary accuracy of directing the wire electrode to the object to be welded, as well as stability of current transfer and steadiness of the welding arc.
Fig. 5 shows a cross cut of the contact tip for gas-metal-aro-welding shown in Fig. 4. The tip comprises two sectors with triangular cross section - 2a1 and 2a2. It is fabricated such that those sections are identical equilateral triangles, being rotated with respect to each other at an angle of 60°
around the tip longitudinal axis. The location of the tip cross cut is denoted by c - c in Fig. 4. The angular rotation of the cross sections 2a ~ and 2a2 of the aperture sectors Ai and Az at an angle of 60°
improves the angular fixing of the wire electrode 4, and the wire electrode occupies the angles of cross sections 2a~ and 2a2 that oppose each other as shown in Fig. 5. The distance between the centers of the wire electrode 4 occupying such a position is 1.4 time smaller as compared to the case when the wire electrode slides within a contact tip whose wire feed aperture has a uniform triangular cross section - see Fig. 3. Hence, this contact tip provides greater tightness of motion of the wire electrode within the aperture, keeping the passability needed, i.e. not decreasing the gap between the wire electrode and the aperture walls.
Fig. 6 and Fig. 7 show tips 1, whose sectors A (Fig. 6) and A~ and A2 (Fig.
7). have triangular cross sections - 2a, 2a~ and 2a2 respectively. The outside surface of the contact tip enveloping those sectors is shaped as a hexagonal prism. Three of its walls 12 are planes, being parallel and equidistant to the sides of the corresponding triangular cross sections 2a, 2a~ and 2az, while the other three walls 11 are convex surfaces and not planes. Consider now sector B (Fig.
6) and sectors Bi and B2, respectively (Fig. 7), whose wire feed aperture has a circular cross section, while the tip outside surface enveloping them has cylindrical shape 13 and the outside tip surface enveloping sectors B
and Bz is threaded (the thread is denoted by 14). Regarding the contact tip shown in Fig. 7, the triangular cross sections 2a~ and 2az are rotated with respect to each other at an angle of 60 °, as shown in Fig. 5. Moreover, the tip in Fig. 7 has four sectors - two sectors A, and ~ with a a triangular cross section of the wire feed aperture, located at the tip front contact end and in the tip middle, respectively, and two sectors Bi and Bz with a circular cross section of the wire feed aperture, one of them located between sectors A~ and Az and the other one - at the tip back (receiving) end. The design of the second sector B2, located at the tip back end, with a circular cross section of its aperture and with outside enveloping threaded cylindrical surface, is proved by the necessity to fabricate thread 14 for mounting the contact tip to the welding apparatus. The specific hexagonal shape of the tip surface, enveloping sectors A, t~ and AE which have aperture with triangular cros s section, is characteristic for a new technological method for the fabrication of tips with various number of sectors with triangular apertures. This method is an object of the present invention, too. Another specificity of such tip is that its outside hexagonal surface is appropriate for screwing the tip to the welding torch or unscrewing it from the welding torch by using a special or even a standard wrench, not needing to cut a special groove for that purpose.
Fig. 8 shows an axonometric view of a contact tip for gas-metal-arc-welding 1 whose wire feed aperture 2 has a triangular cross section and the aperture is shaped as a helix. Fig. 9 shows cross cut of the tip of Fig. 8, but without plotting the wire electrode in order to avoid the excess of details. The helical shape of the aperture is obtained as a result of specific motion of the aperture cross section, combining rectilinear translation of the cross section along the axis O of tip 1 and simultaneous rotation of the cross section around the tip acis. This means that the axis of the helical surface coincides with the axis of the tip. Since the tip axis is perpendicular to the drawing plane of Fig. 9, it is plotted as point O in the figure. Besides, center C of the circle C 1 inscribed in the aperture triangular cross section is the cross point of the bisectrixes of the angles of the triangle, and center C
does not lie on the axis O of the contact tip, i.e, points C and O plotted in Fig. 9 do not coincide.
This condition is necessary for elastic deformation of the wire electrode, i.e. for the occurrence of contact stresses between the wire and the surface of the tip aperture, regardless of whether the wire is rectilinear or arc-shaped. If center C of the inscribed circle C 1 lies on the axis O of the co ntact tip, this means that a rectilinear wire electrode would pass through the tip wire feed aperture with a gap, equal to the difference between the diameter D 1 of the circle inscribed in the aperture cross section and the diameter D2 of the wire electrode. Thus, no contact stresses necessary for current transfer would occur between the wire electrode and the aperture surface. One can obtain uniform distribution of the contact pressure occurnng between the wire electrode and the two arms of the angle q of the triangular cross section of the aperture, when the tip axis O
crosses one of the bisecrixes L. This means that point O in Fig. 9 should lie on one of the bisectrixes L. The bisectrix L
in Fig. 9 coincides with the vertical axis of symmetry of the trig ngular cross section. Center C of the circle C 1 inscribed in the triangular cross section is located at a distance E from the tip axis O (E is eccentricity), while vertex Q which the bisectrix L starts from is located at a distance H from the axis O. When condition H = 0.5 I~/sin (O.Sq) is fulfilled (q = 60° and H = Dl for an equilateral triangle), a rectilinear wire electrode passes through the wire feed aperture without a gap. It is tangential to the walls of the triangular aperture along two helixes, and the angle between the aperture walls is q and the angle vertex is Q. Yet, there is no pressure between the wire electrode and the aperture walls. To provide pressure needed for current transfer, one should keep the condition H < I~/sin (O.Sq) which takes the form H < I~ for an equilateral triangle (q = 60°).
Besides, the decrease of H yields increase of the contact pressure. The occurnng contact pressure between the wire electrode and the surface of the wire feed aperture acting along the two contact helical lines l0a and 10 b (Fig. 8), deforms elastically the wire electrode, and the wire axis becomes helix Oa . Fig. 8 shows six cross sections 2.1 - 2.6 of the triangular wire feed aperture 2 and six cross sections 4.1 - 4.6 of the wire electrode 4. The step of their distribution along the tip axis is 114'h of the step of the helix, i.e. the cross sections are rotated with respect to each other at an angle of 90° around the longitudinal axis of the contact tip I. Points 7a and 7b of contact of the wire electrode 4 with the wire feed apemire 2 are plotted on the first cross sections 2.1 and 4.1, only.
This is done for the sake of clarity. Consider now a tip whose aperture has a helical surface, the aperture cross section is circular and the contact between the wire electrode and the aperture surface is established along a single helix. In contrast to such a tip, however, the present invention is characterized by significant increase of the contact between the wire electrode 4 and the surface of aperture 2, and the contact takes place along two helixes l0a and lOb, since the wire electrode occupies angle q of the triangular aperture 2. Moreover, a specificity of such shape of the wire feed aperture 2 of tip I consists in that without decreasing the aperture passability (i.e. keeping aperture cross section), the force of pressing the wire electrode to the aperture walls is increased, since the wire electrode is forced to follow elastically the helical shape of the aperture. Such a design enables one to realize secure (reliable) contact between the wire electrode 4 and the surface of the wire feed aperture 2 of tip 1. The contact is characteristic with increased contact surface, constant position of the contact spot and constant contact stresses. Thus, one gets steady parameters of the welding arc and weld of good quality.
Fig. 10 shows a cross cut of a contact tip for gas-meta~arc-welding 1, whose wire feed aperture 2 has a helical shape and its cross section is triangular with one curvilinear side 8c, which is shaped as an arc of a circle. The circle 8c has a radius greater than the radius of the wire electrode 4. Wire electrode 4 tangents at points 7a and 7b the two rectilinear arms 8a and 8b of angle q of the triangular cross section of the aperture 2, but it does not touch the third arc-shaped side 8c. The triangular cross section of the aperture 2, having an arc-shaped side 8c and shown in Fig 10, provides a contact between the wire electrode 4 and the wire feed aperture 2 along two lines, as shown in Fig. 8. Moreover, this triangular cross section has smaller dimensions as compared to the dimensions of the triangular cross section with rectilinear sides 8a,, 8b, and 8c,. This tip design is preferable for use with thick wire electrodes (requiring larger dimens ions of the wire feed aperture,) as well as for use in tips with comparatively small outside diameter, when one has to avoid local thiirout of the tip walls and resulting tip overheating.
Fig. 11 shows a contact tip for gas-metal-arc-welding 1 where the wire feed aperture of sector A of the tip l, having a triangular cross section 2a, is fabricated in a separate insert 15. The insert is a tubular body being pressed along its outside surface into an aperture, fabricated at the front end of the tip 1. Current transfer between the tip and the wire electrode is carried out in the triangular aperture 2a of the insert 15. Fig. 12 shows a tip 1, which comprises insert 15 similar to that of the tip shown in Fig. 11, and the insert 15 is screwed to the body of tip 1 by means of thread 16. For that purpose, a step is formed at the back end of the insert where thread is cut.
The step is screwed into a threaded aperture fabricated at the front end of the body of tip 1. The tip design of Fig. 11 and Fig.
12 have the advantage that inserts 15 are replaceable parts and the body of tip 1 can be multiply used. Besides, the inserts 15 can be fabricated from more-expensive alloy with high wear and electro-corrosion resistance or from powder-metallurgical material. This would increase the quality of the tip performance, prolong its term of exploitation and finally yield higher tip efficiency.
Fig. 13 shows an exemplary scheme of the instrument-stamp (matrix). The method of fabricating sector A of tip 1 shown in Fig. 6 or sectors A~ and A~ of the tip shown in Fig. 7 is illustrated on this basis. The tip outside surface enveloping all those sectors is hexagonal. The essence of the method consists in the following: a tubular body 1 f with aperture 2f (plotted by dashed lines in t he figure) is placed in the lower section 19 of the stamp, and the outside surface of the tubular body contacts the shape-forming surfaces 17 of the lower stamp 19. The starting pre-forming position of the upper movable section of the stamp is denoted by 18f and it is plotted by dashed lines. Then, forging follows where the upper movable stamp 18f performs translation towards the lower stamp 19, resulting in plastic deformation of the pre-form between the three surfaces 17 of the instrument.
Thus, the pre-form outside cylindrical surface is shaped into a hexagonal prismatic surface. The hexagonal prism thus obtained has three planes walls 12 which contact the shaping surfaces 17 of the instrument, as well as three curved walls 11. The process of plastic forming proceeds until the fabrication of a product with a desired shape is completed. The position of the upper stamp at the end of the deformation process is denoted by 18, and the final product 1 has a triangular wire feed aperture 2a. A specificity of the method is that the forming impact of the instrument is applied on part of the outside surface of the pra- form, only. Moreover, there are three areas 11 of the pre- form outside surface which are free of contact with the instrument, and the material in those area outflows in a direction opposite to the center of the pre-form cross section. Thus, it is possible for one to transform the inside surface 2f of the wire feed aperture from a cylindrical surface with a circular cross section into a prismatic surface 2a with triangular cross section. This can be done simultaneously with the plastic shaping of the outside hexagonal surface of the tip, without applying an impact of the forming instrument (arbor) on the inside surface. What is specific for the method proposed is that by appropriate choice of the degrees of deformation, geometry of the pre-form and geometry of the facial surfaces 17 of the instrument, one can fabricate contact tips with various geometry of the aperture cross section.
Fig. 14 shows the principal scheme of a rolling device where one can use the same method (as in Fig. 13) of plastic forming, applied for the fabrication of sectors A or Ai and A2 shown in Fig. 6 and Fig. 7, respectively, wherein the sectors have hexagonal outside enveloping surface. Tubular cylindrical pre-form if is introduced into a rolling stand which comprises three identical rolls 20, whose axes 21 lie in one and the same plane (the drawing plane), and the axes conclude angles of 120° between each other. The longitudinal axis of the tubular pre-form if is perpendicular to the plane where the roll axes lie and its position is symmetrical with respect to those axes. The direction of introducing the tubular pre- form into the rolling stand coincides with the direction of roll rotation, and the rolls deform the pr~form and translate it in the same direction. One can deform the pre-form along its whole length or one can deform a sector of it, only (sector A in Fig. 6). The pre-form exits the rolling stand shaped as a hexagonal ~ism, while the wire feed aperture is shaped as a triangular aperture 2a. In fact, the characteristic features and the advantages of the method of forging described above and illustrated in Fig. 13 (a scheme of power impact and metal plastic outflow) are valid here, too. The use of a rolling stand as a device for the fabrication of the contact tip is especially appropriate when the tip has outside hexagonal surface along its whole length, since the method of tip fabrication is especially productive in that case.
~s The optimal gap between the welding wire electrode and the wire feed aperture walls is experimentally found, regarding a contact tip whose aperture has a triangular cross section. The experiments are performed, involving welding wire electrodes with diameters 0.8, 1.0, 1.2, 1.4, 1.6 mm and tips 25, 30 and 40 mm long. The cross section of the tip wire feed aperture is an equilateral triangle and it is uniform along the whole tip length. The experimental results are specified in the table given below.
D1/D2 Evaluation Remark 1,05 Wire feed is pered.
1,07 I Successfizl tip 1,12 I Successful tip 1,14 I Successful tip 1,20 I Successful tip 1,22 o Current transfer is unstable) These results illustrate that tips, whose ratio between the diameter of D~ of the circle inscribed in the aperture triangular cross section and the diameter Dz of the welding wire electrode is within ranges 1, 07 -1, 20, are characterized by good perfomlance. For ratio values under 1.07, wire passability is deteriorated (the wire electrode often blocks within the wire feed aperture) while for ratio values over 1,20 current transfer is deteriorated and sometimes wire welds to the wire feed aperture of the tip.
The nozzle blows inert or active gas over the weld puddle, separating atmospheric air from the weld puddle. This avoids unwanted reactions of the molten material with the surrounding air. Thus, one can obtain clean weld of good quality. In most welding apparatuses, the welding wire electrode is wound on a spool, and it is unwound by the welding wire feeder. The wire electrode is automatically fed off the spool and into the contact tip welding torch. The wire electrode is unwound off the spool, having a specific cast which is arcuate in nature, and it is elastically straightened in the wire feed aperture and is pressed to the wire feed aperture walls. This effect is favo ~eable for the current transfer, since it maintains good electric conductivity between the welding wire electrode and the surface of the wire feed aperture. Wire must move smoothly through the tip aperture without jerking, thus providing exact and high performance welding. The wire feed aperture of the contact tip for gas-metal arc welding is made with dimension tolerance between the wire electrode and the wire feed aperture.
However, the increase of the wire/aperture gap over a definite limit yields poor contact between the wire electrode and the surface of the wire feed aperture, deteriorating the welding process. The presence of debris carried by the surface of the wire electrode and introduced in the wire feed aperture or formed in the wire feed aperture as a result of electric erosion increases the risk of choking the wire feed aperture, especially when the gap is small. These and a number of other requirements to the contact tip for gas-metal arc welding, contradicting to each other, explain the existence of different constructional solutions of the contact tip. Yet, each of them has specific disadvantages.
The most popular contact tip for ga~metal arc welding is a tubular body with a cylindrical central wire feed aperture. A disadvantage of such a tip is its short term of exploitation, due to wear caused by intensive abrasion or electrical erosion. This is so, since the current loads are too great (welding current has power of 100-800 A). Moreover, current is transferred by means of a three-point contact between the welding wire electrode and the contact tip, only (contact at the back receiving end of the wire feed aperture, contact in the aperture middle and at contact the aperture front contact end), and the contact areas are too small. Besides, pressure along the contact surfaces is insignificant and of variable magnitude. The trend of one to decrease the wire/aperture gap in order to improve the contact does not increase the contact area, but worsens the passability of the wire feed aperture and increases the risk of blockage of the wire electrode within the aperture.
Besides, since the wire feed aperture has a circular cross section, the wire electrode rotates within the aperture during welding, which impedes the exact wire feed towards the weld puddle. Due the wire electrode rotation and electric erosion, contact areas change in time their sizes and the process of current transfer becomes norrsteady. As a result, the welding arc becomes instable which yielding weld of poor quality. The outlined norrsteadiness of the current transfer also yields generation of sporadic liquid metal bursts, which fall into and stick to the weld and to the area surrounding it. Thus, the weld quality worsens additionally. On the other hand, bursts being regularly expelled from the weld zone as miniature droplets, bind and build up to the contact end of the contact tip. Thus, they yield additional thermal loads, tip oxidation and burn-through etc. These effects decrease the exploitation term of the contact tip for gas~metal arc welding. Burst can sometimes enter the zone of the wire feed aperture outlet, disturbing motion of the wire electrode and yielding instability of wire electrode transport, poor weld initiation or tip failure.
Other constructional solutions of a contact tip for gas-metal arc welding are also known - see, for instance patent BG 63039 B 1, where the cross section of the tip wire feed aperture is not circular and the cross section boundary is mt a smooth line, but it has at least one kink (one angle).
However, these solutions manage to eliminate some of the outlined functional disadvantages of a contact tip for gas-metal arc welding with a circular cross section, and the positive effects are result of the following reasons: the rotation of the wire electrode in the tip wire feed aperture is significantly suppressed, since wire electrode occupies one angle of the aperture cross section and it is thus fixed (i.e. the arc is stabilized); the number of contact points between the wire electrode and the walls of the wire feed aperture, at the aperture back receiving end, in its middle section and at the aperture front contact end, is doubled, since two-point contact is attained on the angle arms, while the contact in a tip with a circular cross section takes place at one point; contact forces acting between the wire electrode and the aperture become larger. Moreover, considering tips with triangular wire feed apertures, the welding wire electrode contacts the tip along a line, lying in one of the planes of the tip prismatic wire feed aperture. In addition, such contact is established at three more points, lying in the other two planes of the prismatic wire feed aperture - at the tip back receiving end, in its middle section and at the tip front contact end. The problem of these contact tips for ga~metal arc welding is how to find the gap between the wire electrode and the tip aperture.
Considering a contact tip for gas-metal arc welding whose cross section is triangular, the wire electrode should have a diameter, smaller than that of the circle, inscribed in the triangle. Thus, wire could pass through the tip cross section. Yet, the assumption of the difference between the diameter of the circle inscribed in the aperture triangular cross section and the diameter of the wire electrode as a measure of looseness is not appropriate and yields unreliable results.
This is so, since the wire electrode, passing through the wire feed aperture, occupies one of the angles of the triangle, and its elastic pre-stressing relaxes to a certain extent. Hence, one should know the optimal practical parameters of the triangular cross section, thus providing optimal conditions of current transfer and norrdisturbed and smooth motion of the wire electrode through the triangular wire feed aperture.
Other constructional solutions of contact tips for gas-metal arc welding (CT) are also known - see patents BG 60184 and CA 1247707, where the axis of the wire feed aperture is a helix. Moreover, a linear contact between the wire electrode and the tip wire feed aperture is attained along a helix.
This contact is much better than the three-point contact attained in a tip with a circular cross section.
It also is comparable to the contact in tips with noircircular cross section.
Besides (as in a contact tip with a norrcircular aperture) contact pressure between the wire electrode and the wire feed aperture is higher than pressure in tips with a circular wire feed aperture, since the wire e~ctrode is forced to change continuously and elastically its curvature along the whole length of the contact tip.
A disadvantage of such contact tip for gas-metal arc welding (patent CA1247707) relates to the specificity that the helical passage for wire motion is laterally open towards the tip outside surface, forcing the helical tip aperture to make at least one full rotation.
Otherwise, the wire electrode would go out of the contact tip and it could not be forced to follow the contact tip axis. The specificity that the wire electrode passage is open yields two more problems, which concern metal spatter binding and building up to the front end of the laterally open passage and the exact direction of the wire electrode towards the weld zone. This implies additional mounting of an insert at the front contact end of the tip, and this complication, together with the non-technological construction, is a reason for the tip high cost.
Considering a number of cases of welding, one should use contact tip for gas metal arc welding with significantly increased length. However, the increase of the tip length yields increase of friction during wire electrode motion, which hampers wire electrode feeding and sometimes even blocks the wire electrode in the wire feed aperture. Constructional solutions are known, where this problem is solved by fabricating the contact tip as a cylindrical tube with circular cross section of the wire feed aperture. Moreover, the tip has smaller outside and inside diameters at its front contact sector, as compared to the outside and inside diameters of the rest part of the tip, i.e.
the tip is a monolithic body consisting of two tubular sectors with different outside and inside diameters. The sector with smaller outside and inside diameters has a length, approximately equal to the length of a regular contact tip for gas-metal arc welding, and it is located at the front contact end of the tip, i.e. in the area where the wire electrode projects out of the contact tip and is fed to the weld. The electric contact between the contact tip and the wire electrode is achieved in this sector, which is comparably shorter and the wire feed aperture has a smaller diameter. The rest part of the tip has larger outside and inside diameters, so that the smooth motion of the wire electrode would not be disturbed. However, these tips have the disadvantages inherent to all contact tips for gas-metal arc welding with a circular aperture, considered so far: limited three-point tip/wire contact, fast abrasion and electric erosion and short term of exploitation.
Some solutions, considering the external design of a contact tip for gas-metal arc welding are known, where a groove is fabricated on the tip external cylindrical surface.
Yet, the groove function is not related to the welding process, but the groove is cut for one to hold the tip by a wrench for mounting it to and/or dismounting it from the torch. Besides, groove cut is an additional operation which is not part of the basic technologies of fabricating the tip a~pper tubular body (pressing, drawing, mechanical drilling etc.) and it increases the tip total cost.
SUMMARY OF THE INVENTION
The aim of the present invention is to provide a new construction of a contact tip for gas-metal-arc-welding, which would significantly eliminate the disadvantages of the contact tips discussed so far, increasing the contact areas and contact stresses which occur between the wire electrode and the tip wire feed aperture, but without decreasing wire electrode passability. At the same time, the design proposed would limit the rotation of the wire electrode within the wire feed aperture. The profits of the invention are as follows: significant improvement of current transfer and decrease of the generation of melted metal spatters; limitation of the possibility of blockage of the wire electrode within the wire feed aperture as a result of large friction stresses (for contact tips with large length) or as a result of the small gap between the wire electrode and the wire feed aperture; providing great variety of combinations of contact areas and contact stresses; thus guaranteeing effective conditions of current transfer for a wide range of lengths of contact tips for gas-meta~arc-welding, the range comprising very short and very long contact tips. Besides, the tip construction is technologically appropriate for smooth tip fabrication.
The aim of the invention is attained by designing a contact tip for gas-metal-arc-welding, fabricated from copper, copper alloy or powder metallurgy (PM) sintered material having high electrical and thermal conductivity. The contact tip is for use in a welding torch and it serves to feed the wire electrode to the weld and to pass the electric charge from the torch to the wire electrode. The contact tip comprises a tubular body with a central passable wire feed aperture whose axis is rectilinear. The aperture has a back receiving end on the side where the wire electrode is fed to the contact tip aperture through a specially shaped inlet cone. The aperture also has a front contact end on the side where the wire electrode projects from the tip, being directed to the weld.
Considering an aspect of the invention, the wire feed aperture of the contact tip does not have a uniform cross section along its whole length, but it has at least one sector, which starts at the tip front contact end and its cross section is triangular while its length is smaller than the whole aperture length The rest of the wire feed aperture has a circular cross section with a diame ter, larger than the s diameters of the circle inscribed in the cross section of any sector of the wire feed aperture which has triangular cross section.
Considering one of the preferable technological solutions of the present invention, the wire feed aperture of the contact tip comprises three sectors, two of which have a triangular cross section and are located at both tip ends. The third sector occupies the rest middle part of the wire feed aperture and has a circular cross section, while its diameter is larger than the diameters of the circles inscribed in the triangular cross sections of the above said two aperture sectors.
Considering another preferable technological solution of the present invention, the wire feed aperture of the contact tip comprises four sectors. Two of them have triangular cross section, and the first one is located at the tip front contact end while the second one is located in the middle part of the contact tip. The wire feed aperture between these two sectors, together with the aperture of the tip back receiving end, have a circular cross section with a diameter larger than the diameters of the circles inscribed in the triangular cross sections of the above said two aperture sectors.
Considering a preferable variant of the cottact tip, related to tips that have two sectors with triangular wire feed apertures, the said sectors have identical cross sections which are equilateral triangles. The said sectors are rotated with respect to each other around the aperture longitudinal axis at an angle of 60°.
As for another aspect of the present invention, the tip outside surface, enveloping the said tip sectors whose aperture cross section is triangular, is shaped as a hexagonal prism with three plane and three curved walls. Besides, all prism walls are parallel to the tip longitudinal axis. Moreover, the plane walls of the prism are parallel and equidistant to the corresponding inside walls of the triangular wire feed aperture of the said sectors. As for the subsequent tip sectors whose aperture has a circular cross section, the outside tip surface enveloping them is cylindrical.
As for another aspect of the present invention and considering the tip sector located at the tip front contact end and having a triangular cross section, the ratio between the diameter of the circle inscribed in the triangular cross section of the said tip sector and the diameter of the wire electrode is 1.15 - 1.25.
As for another aspect of the present invention, the tip sector located at the tip front contact end has a triangular aperture, and the aperture surface is helical, while the aperture longitudinal axis coincides with the longitudinal axis of the tip. Besides, the center of the circle inscribed in the triangular cross section of the said sector is the cross point of the bisectrixes of the triangle, and the said circle center does not lie on the tip axis.
In a preferable version of the present invention related to contact tips for gas-metal~arc-welding where the surface of the wire feed aperture is helical, the cross section of the said wire feed aperture is an equilateral triangle, and the bisectrix of one of the angles of the said triangle crosses the axis of the contact tip at a point, whose distance to the vertex of the said angle is smaller than the diameter of the wire electrode.
Considering a preferable version of the present invention related to contact tips for gas-metal-arc-welding where the surface of the wire feed aperture is helical and the cross section of the said aperture is triangular, the bisectrix of one of the angles of the said triangular cross section crosses the axis of the contact tip at a point whose distance to the vertex of the said angle is smaller than the radius of the wire electrode divided by the sinus of half of the said angle.
Considering a preferable version of the present invention related to contact tips for gas-metal-arc-welding where the wire feed aperture has a helical surface and the cross section of the wire feed aperture is triangular, one of the sides of the said triangular cross section is curvilinear and convex while the other two sides of the said triangular cross section are rectilinear. The curvilinear side of the said triangular cross section is an arc of a circle, while the diameter of the said circle is larger than the diameter of the wire electrode. The said arc is equidistant to a circle having a diameter equal to the diameter of the wire electrode, and the said circle tangents the arms of the angle concluded by the said rectilinear sides of the aperture triangular cross section.
As for another aspect of the present invention, a sector of the wire feed aperture being located at the tip front contact end and having a triangular cross section, is fabricated as a separate insert. The said insert is pressed in an aperture bored through the tip front contact end or the said insert is threaded to the tip front contact end.
As for another aspect of the present invention, a method of fabricating a contact tip for gas-metal-arc-welding is proposed. The tip has sectors with triangular wire feed aperture while the outside surface enveloping the said sectors is shaped as a hexagonal prism. Using the method of tip fabrication proposed, processes of plastic forming - forging or rolling are applied. Furthermore, the said method comprises an initial fabrication stage, in which a cylindrical tubular pre-form of copper or copper alloy, with a passable aperture of circular cross section, is placed in a matrix for forging or in a rolling stand for rolling. Then, a second stage of plastic forming follows, resulting in the plastic forming of the tubular pre-form or of a sector of the tubular pre-form into a body, whose deformed section is a tube with a hexagonal outside enveloping surface and which has a passable wire feed aperture with a triangular cross section. According to the method proposed, the said outside enveloping hexagonal surface and the said wire feed aperture with a triangular cross section are obtained simultaneously as a result of the power impact of the forming instrument. The power impact is applied on the outside surface of the pre- form, only, and the power impact is directed perpendicularly to the pre-form axis. Besides, the instrument shape-forming faces which contact the pre-form and exercise power impact on it, conclude with each other angles which are equal to the angles of the cross section of the said triangular aperture .
BRIEF DESCRIPTION OF THE DRAWINGS
The enclosed figures provide a better clarification of the essence of the present invention The figures illustrate the following characteristic features of the contact tip for gas-metal-arc-welding:
Fig. 1 shows a longitudinal section of the contact tip together with the wire electrode inserted in it.
Fig. 2 shows a longitudinal section of a contact tip with two-sector wire feed aperture.
Fig. 3 shows an axonometric view of the position of the wire electrode in a wire feed aperture with a triangular cross section.
Fig. 4 shows a longitudinal section of a contact tip with a three-sector wire feed aperture.
Fig. 5 shows a cross section c - c of the contact tip in Fig. 4 with triangular wire feed apertures, wherein the aperture cross sections are rotated with respect to each other at an angle of 60° around the tip longitudinal axis.
Fig. 6 shows an axonometric view of a contact tip, wherein part of its outside enveloping surface is shaped as a hexagonal prism.
Fig. 7 shows an axonometric view of a four-sector contact tip with a wire feed aperture as shown in Fig. 5.
Fig. 8 shows an axonometric view of a contact tip with a helical aperture which has a triangular cross section.
Fig. 9 shows a cross section of a contact tip with a helical wire feed aperture with a triangular cross section.
Fig. 10 shows a cross section of a contact tip with a helical wire feed aperture, whose triangular cross section has one convex aro-shaped side.
Fig. I 1 shows a longitudinal section of a contact tip with a hammered-in insert, wherein the insert has an aperture with a triangular cross section.
Fig. 12 shows a longitudinal section of a contact tip with a threaded insert, wherein the insert has an aperture with a triangular cross section.
Fig. 13 shows a cross section of a stamp (matrix) for the fabrication of a contact tip whose aperture has a triangular cross section and whose outside enveloping surface is hexagonal.
Fig. 14 shows a rolling stand for the fabrication of a contact tip whose aperture has a triangular cross section and whose outside enveloping surface is hexagonal.
DETAILED DESCRIPTION OF THE INVENTION
Considering the enclosed figures 1 -14, the part specified as position 1 generally maps a contact tip for use in a welding torch which is not shown in the figure.
As seen in Fig. 1, the contact tip 1 is a tubulax body with a central passable wire feed aperture 2 and the aperture axis is rectilinear. The aperture 2 has a back receiving end Ib on the side where the wire electrode 4 is fed in the aperture 2 of the contact tip 1 through a specially shaped inlet cone 5. The wire feed aperture 2 also has a front contact end if on the side where the wire electrode 4 projects from the contact tip 1 and is directed to the weld 3. The contact tip is fixed to the element 6 (diffuser) through its receiving end lb. The contact tip through its receiving end lb. is fixed either to the element 6 (diffixser) of the welding torch or to the carrier of the welding apparatus. The wire electrode 4 which has a natural curvature passes through the wire feed aperture 2 of the contact tip I, deforms elastically and is thus pressed to the walls of the aperture 2 at points 7.
Fig. 2 shows the contact tip I, wherein the wire feed aperture 2 does not have a uniform cross section along its whole length, but sector A of the wire feed aperture 2 starts from the front contact end of the contact tip I and has a triangular cross section 2a. A second sector B is shaped at the back receiving end of the contact tip I and it has a circular cross section 2b. T'he second sector B
starts from the receiving inlet cone 5 and stretches to the first sector A.
The diameter of the aperture of the second sector B is larger than the diameter of the circle inscribed in the triangular cross section 2a of the first sector A of the wire feed aperture 2. As for the contact tip under consideration the effective contact realizing current transfer from the tip I to the wire electrode 4 occurs in sector A of the wire feed aperture. The aperture sector A has a triangular cross section 2a and the wireJaperture gap is smaller. The character of the contact is shown in Fig. 3.
The position of the wire electrode 4 in the prismatic triangular sector A of the wire feed aperture 2, shown in Fig. 3, is the most stable one as compared to all possible positions of the wire electrode.
This is so, since minimum of the potential energy of elastic stressing of the wire electrode 4 is attained in this wire position. The wire electrode 4 realizes linear contact 10 with the wall 8a of the triangular prismatic sector A of the wire feed aperture 2. 'The wire electrode 4 additionally contacts the other two sides of the triangular prismatic sector A at three more points (at two points 7b located at both ends of wall 8b and at one point 7c located in the middle of wall 8c). While current transfer in a two-sector contact tip (Fig.2) is realized in sector A which has a triangular cross section, as outlined above, sector B of the contact tip I with a circular cross section of the wire feed aperture 2 has a function of elongating the contact tip I to the length needed. This is done in accordance with the specific requirements of the welding machinery and technology employed, without increasing the wire resistance to push out of the aperture. Thus, one can attain balance between the optimal conditions of current transfer (characterized by appropriate gaps, increased contact areas and pressure and stable angular fixing) and good passability of the wire electrode, especially in contact tips with larger length. As a result, the welding are is stable, the amount of spatter is significantly smaller, the accuracy of directing the wire electrode to the weld is higher, the probability of wire electrode blockage within the wire feed aperture is decreased and the exploitation term of the contact tip is increased. As a whole, the weld is of high quality.
Fig. 4 shows a contact tip I whose wire feed aperture 2 has three sectors - A~
, Az and B. Sectors A~
and Az are located at the tip front (contact) and at its back (receiving) end (just at the inlet cone 5).
Those sectors have triangular cross sections 2a~ and 2a2. A third sector B is located between sectors A~ and AQ, in the tip middle section, and sector B has a circular cross section 2b whose diameter is io larger than the diameter of the circles inscribed in the triangular cross sections 2a~ and 2a2 of sectors A~ and A2. Such a design of a contact tip for gas-meta~arc-welding is preferable when the specific conditions of welding require that the tip length be significantly larger than the length of an ordinary and most common tip. Hence, it is useful for one to divide the triangular sector of the wire feed aperture into two parts (i.e. into the two sectors ~ and AQ discussed above, as shown in Fig. 4).
They are located at both tip ends, since wire fixing along a larger length yields stronger resstance to rotation of the wire electrode. Thus, one can attain the necessary accuracy of directing the wire electrode to the object to be welded, as well as stability of current transfer and steadiness of the welding arc.
Fig. 5 shows a cross cut of the contact tip for gas-metal-aro-welding shown in Fig. 4. The tip comprises two sectors with triangular cross section - 2a1 and 2a2. It is fabricated such that those sections are identical equilateral triangles, being rotated with respect to each other at an angle of 60°
around the tip longitudinal axis. The location of the tip cross cut is denoted by c - c in Fig. 4. The angular rotation of the cross sections 2a ~ and 2a2 of the aperture sectors Ai and Az at an angle of 60°
improves the angular fixing of the wire electrode 4, and the wire electrode occupies the angles of cross sections 2a~ and 2a2 that oppose each other as shown in Fig. 5. The distance between the centers of the wire electrode 4 occupying such a position is 1.4 time smaller as compared to the case when the wire electrode slides within a contact tip whose wire feed aperture has a uniform triangular cross section - see Fig. 3. Hence, this contact tip provides greater tightness of motion of the wire electrode within the aperture, keeping the passability needed, i.e. not decreasing the gap between the wire electrode and the aperture walls.
Fig. 6 and Fig. 7 show tips 1, whose sectors A (Fig. 6) and A~ and A2 (Fig.
7). have triangular cross sections - 2a, 2a~ and 2a2 respectively. The outside surface of the contact tip enveloping those sectors is shaped as a hexagonal prism. Three of its walls 12 are planes, being parallel and equidistant to the sides of the corresponding triangular cross sections 2a, 2a~ and 2az, while the other three walls 11 are convex surfaces and not planes. Consider now sector B (Fig.
6) and sectors Bi and B2, respectively (Fig. 7), whose wire feed aperture has a circular cross section, while the tip outside surface enveloping them has cylindrical shape 13 and the outside tip surface enveloping sectors B
and Bz is threaded (the thread is denoted by 14). Regarding the contact tip shown in Fig. 7, the triangular cross sections 2a~ and 2az are rotated with respect to each other at an angle of 60 °, as shown in Fig. 5. Moreover, the tip in Fig. 7 has four sectors - two sectors A, and ~ with a a triangular cross section of the wire feed aperture, located at the tip front contact end and in the tip middle, respectively, and two sectors Bi and Bz with a circular cross section of the wire feed aperture, one of them located between sectors A~ and Az and the other one - at the tip back (receiving) end. The design of the second sector B2, located at the tip back end, with a circular cross section of its aperture and with outside enveloping threaded cylindrical surface, is proved by the necessity to fabricate thread 14 for mounting the contact tip to the welding apparatus. The specific hexagonal shape of the tip surface, enveloping sectors A, t~ and AE which have aperture with triangular cros s section, is characteristic for a new technological method for the fabrication of tips with various number of sectors with triangular apertures. This method is an object of the present invention, too. Another specificity of such tip is that its outside hexagonal surface is appropriate for screwing the tip to the welding torch or unscrewing it from the welding torch by using a special or even a standard wrench, not needing to cut a special groove for that purpose.
Fig. 8 shows an axonometric view of a contact tip for gas-metal-arc-welding 1 whose wire feed aperture 2 has a triangular cross section and the aperture is shaped as a helix. Fig. 9 shows cross cut of the tip of Fig. 8, but without plotting the wire electrode in order to avoid the excess of details. The helical shape of the aperture is obtained as a result of specific motion of the aperture cross section, combining rectilinear translation of the cross section along the axis O of tip 1 and simultaneous rotation of the cross section around the tip acis. This means that the axis of the helical surface coincides with the axis of the tip. Since the tip axis is perpendicular to the drawing plane of Fig. 9, it is plotted as point O in the figure. Besides, center C of the circle C 1 inscribed in the aperture triangular cross section is the cross point of the bisectrixes of the angles of the triangle, and center C
does not lie on the axis O of the contact tip, i.e, points C and O plotted in Fig. 9 do not coincide.
This condition is necessary for elastic deformation of the wire electrode, i.e. for the occurrence of contact stresses between the wire and the surface of the tip aperture, regardless of whether the wire is rectilinear or arc-shaped. If center C of the inscribed circle C 1 lies on the axis O of the co ntact tip, this means that a rectilinear wire electrode would pass through the tip wire feed aperture with a gap, equal to the difference between the diameter D 1 of the circle inscribed in the aperture cross section and the diameter D2 of the wire electrode. Thus, no contact stresses necessary for current transfer would occur between the wire electrode and the aperture surface. One can obtain uniform distribution of the contact pressure occurnng between the wire electrode and the two arms of the angle q of the triangular cross section of the aperture, when the tip axis O
crosses one of the bisecrixes L. This means that point O in Fig. 9 should lie on one of the bisectrixes L. The bisectrix L
in Fig. 9 coincides with the vertical axis of symmetry of the trig ngular cross section. Center C of the circle C 1 inscribed in the triangular cross section is located at a distance E from the tip axis O (E is eccentricity), while vertex Q which the bisectrix L starts from is located at a distance H from the axis O. When condition H = 0.5 I~/sin (O.Sq) is fulfilled (q = 60° and H = Dl for an equilateral triangle), a rectilinear wire electrode passes through the wire feed aperture without a gap. It is tangential to the walls of the triangular aperture along two helixes, and the angle between the aperture walls is q and the angle vertex is Q. Yet, there is no pressure between the wire electrode and the aperture walls. To provide pressure needed for current transfer, one should keep the condition H < I~/sin (O.Sq) which takes the form H < I~ for an equilateral triangle (q = 60°).
Besides, the decrease of H yields increase of the contact pressure. The occurnng contact pressure between the wire electrode and the surface of the wire feed aperture acting along the two contact helical lines l0a and 10 b (Fig. 8), deforms elastically the wire electrode, and the wire axis becomes helix Oa . Fig. 8 shows six cross sections 2.1 - 2.6 of the triangular wire feed aperture 2 and six cross sections 4.1 - 4.6 of the wire electrode 4. The step of their distribution along the tip axis is 114'h of the step of the helix, i.e. the cross sections are rotated with respect to each other at an angle of 90° around the longitudinal axis of the contact tip I. Points 7a and 7b of contact of the wire electrode 4 with the wire feed apemire 2 are plotted on the first cross sections 2.1 and 4.1, only.
This is done for the sake of clarity. Consider now a tip whose aperture has a helical surface, the aperture cross section is circular and the contact between the wire electrode and the aperture surface is established along a single helix. In contrast to such a tip, however, the present invention is characterized by significant increase of the contact between the wire electrode 4 and the surface of aperture 2, and the contact takes place along two helixes l0a and lOb, since the wire electrode occupies angle q of the triangular aperture 2. Moreover, a specificity of such shape of the wire feed aperture 2 of tip I consists in that without decreasing the aperture passability (i.e. keeping aperture cross section), the force of pressing the wire electrode to the aperture walls is increased, since the wire electrode is forced to follow elastically the helical shape of the aperture. Such a design enables one to realize secure (reliable) contact between the wire electrode 4 and the surface of the wire feed aperture 2 of tip 1. The contact is characteristic with increased contact surface, constant position of the contact spot and constant contact stresses. Thus, one gets steady parameters of the welding arc and weld of good quality.
Fig. 10 shows a cross cut of a contact tip for gas-meta~arc-welding 1, whose wire feed aperture 2 has a helical shape and its cross section is triangular with one curvilinear side 8c, which is shaped as an arc of a circle. The circle 8c has a radius greater than the radius of the wire electrode 4. Wire electrode 4 tangents at points 7a and 7b the two rectilinear arms 8a and 8b of angle q of the triangular cross section of the aperture 2, but it does not touch the third arc-shaped side 8c. The triangular cross section of the aperture 2, having an arc-shaped side 8c and shown in Fig 10, provides a contact between the wire electrode 4 and the wire feed aperture 2 along two lines, as shown in Fig. 8. Moreover, this triangular cross section has smaller dimensions as compared to the dimensions of the triangular cross section with rectilinear sides 8a,, 8b, and 8c,. This tip design is preferable for use with thick wire electrodes (requiring larger dimens ions of the wire feed aperture,) as well as for use in tips with comparatively small outside diameter, when one has to avoid local thiirout of the tip walls and resulting tip overheating.
Fig. 11 shows a contact tip for gas-metal-arc-welding 1 where the wire feed aperture of sector A of the tip l, having a triangular cross section 2a, is fabricated in a separate insert 15. The insert is a tubular body being pressed along its outside surface into an aperture, fabricated at the front end of the tip 1. Current transfer between the tip and the wire electrode is carried out in the triangular aperture 2a of the insert 15. Fig. 12 shows a tip 1, which comprises insert 15 similar to that of the tip shown in Fig. 11, and the insert 15 is screwed to the body of tip 1 by means of thread 16. For that purpose, a step is formed at the back end of the insert where thread is cut.
The step is screwed into a threaded aperture fabricated at the front end of the body of tip 1. The tip design of Fig. 11 and Fig.
12 have the advantage that inserts 15 are replaceable parts and the body of tip 1 can be multiply used. Besides, the inserts 15 can be fabricated from more-expensive alloy with high wear and electro-corrosion resistance or from powder-metallurgical material. This would increase the quality of the tip performance, prolong its term of exploitation and finally yield higher tip efficiency.
Fig. 13 shows an exemplary scheme of the instrument-stamp (matrix). The method of fabricating sector A of tip 1 shown in Fig. 6 or sectors A~ and A~ of the tip shown in Fig. 7 is illustrated on this basis. The tip outside surface enveloping all those sectors is hexagonal. The essence of the method consists in the following: a tubular body 1 f with aperture 2f (plotted by dashed lines in t he figure) is placed in the lower section 19 of the stamp, and the outside surface of the tubular body contacts the shape-forming surfaces 17 of the lower stamp 19. The starting pre-forming position of the upper movable section of the stamp is denoted by 18f and it is plotted by dashed lines. Then, forging follows where the upper movable stamp 18f performs translation towards the lower stamp 19, resulting in plastic deformation of the pre-form between the three surfaces 17 of the instrument.
Thus, the pre-form outside cylindrical surface is shaped into a hexagonal prismatic surface. The hexagonal prism thus obtained has three planes walls 12 which contact the shaping surfaces 17 of the instrument, as well as three curved walls 11. The process of plastic forming proceeds until the fabrication of a product with a desired shape is completed. The position of the upper stamp at the end of the deformation process is denoted by 18, and the final product 1 has a triangular wire feed aperture 2a. A specificity of the method is that the forming impact of the instrument is applied on part of the outside surface of the pra- form, only. Moreover, there are three areas 11 of the pre- form outside surface which are free of contact with the instrument, and the material in those area outflows in a direction opposite to the center of the pre-form cross section. Thus, it is possible for one to transform the inside surface 2f of the wire feed aperture from a cylindrical surface with a circular cross section into a prismatic surface 2a with triangular cross section. This can be done simultaneously with the plastic shaping of the outside hexagonal surface of the tip, without applying an impact of the forming instrument (arbor) on the inside surface. What is specific for the method proposed is that by appropriate choice of the degrees of deformation, geometry of the pre-form and geometry of the facial surfaces 17 of the instrument, one can fabricate contact tips with various geometry of the aperture cross section.
Fig. 14 shows the principal scheme of a rolling device where one can use the same method (as in Fig. 13) of plastic forming, applied for the fabrication of sectors A or Ai and A2 shown in Fig. 6 and Fig. 7, respectively, wherein the sectors have hexagonal outside enveloping surface. Tubular cylindrical pre-form if is introduced into a rolling stand which comprises three identical rolls 20, whose axes 21 lie in one and the same plane (the drawing plane), and the axes conclude angles of 120° between each other. The longitudinal axis of the tubular pre-form if is perpendicular to the plane where the roll axes lie and its position is symmetrical with respect to those axes. The direction of introducing the tubular pre- form into the rolling stand coincides with the direction of roll rotation, and the rolls deform the pr~form and translate it in the same direction. One can deform the pre-form along its whole length or one can deform a sector of it, only (sector A in Fig. 6). The pre-form exits the rolling stand shaped as a hexagonal ~ism, while the wire feed aperture is shaped as a triangular aperture 2a. In fact, the characteristic features and the advantages of the method of forging described above and illustrated in Fig. 13 (a scheme of power impact and metal plastic outflow) are valid here, too. The use of a rolling stand as a device for the fabrication of the contact tip is especially appropriate when the tip has outside hexagonal surface along its whole length, since the method of tip fabrication is especially productive in that case.
~s The optimal gap between the welding wire electrode and the wire feed aperture walls is experimentally found, regarding a contact tip whose aperture has a triangular cross section. The experiments are performed, involving welding wire electrodes with diameters 0.8, 1.0, 1.2, 1.4, 1.6 mm and tips 25, 30 and 40 mm long. The cross section of the tip wire feed aperture is an equilateral triangle and it is uniform along the whole tip length. The experimental results are specified in the table given below.
D1/D2 Evaluation Remark 1,05 Wire feed is pered.
1,07 I Successfizl tip 1,12 I Successful tip 1,14 I Successful tip 1,20 I Successful tip 1,22 o Current transfer is unstable) These results illustrate that tips, whose ratio between the diameter of D~ of the circle inscribed in the aperture triangular cross section and the diameter Dz of the welding wire electrode is within ranges 1, 07 -1, 20, are characterized by good perfomlance. For ratio values under 1.07, wire passability is deteriorated (the wire electrode often blocks within the wire feed aperture) while for ratio values over 1,20 current transfer is deteriorated and sometimes wire welds to the wire feed aperture of the tip.
Claims (11)
1. A contact tip for gas-metal-arc-welding, fabricated from copper, copper alloy or powder metallurgy sintered material which have high electrical and thermal conductivity, the said contact tip being for use in a welding torch that feedingly guides wire electrode toward a work piece and passes the electric charge from the torch and to the wire electrode, the contact tip consisting of:
a tubular body with a central wire feed passable aperture whose axis is rectilinear:
said wire feed aperture having a back receiving end on the side where the wire electrode is fed to the contact tip aperture through a specially shaped inlet cone:
said wire feed aperture also having a front contact end on the side where the wire electrode projects from the tip, being directed to the weld:
said wire feed aperture not having a uniform cross section along its whole length, but having at least one sector of its length whose cross section is triangular, the said sector starting at the tip front contact end and the length of the said sector being smaller than the whole aperture length, while the rest part of the wire feed aperture having a circular cross section with a diameter, larger than the diameter of the circle inscribed in the cross section of any sector of the wire feed aperture which has a triangular cross section.
a tubular body with a central wire feed passable aperture whose axis is rectilinear:
said wire feed aperture having a back receiving end on the side where the wire electrode is fed to the contact tip aperture through a specially shaped inlet cone:
said wire feed aperture also having a front contact end on the side where the wire electrode projects from the tip, being directed to the weld:
said wire feed aperture not having a uniform cross section along its whole length, but having at least one sector of its length whose cross section is triangular, the said sector starting at the tip front contact end and the length of the said sector being smaller than the whole aperture length, while the rest part of the wire feed aperture having a circular cross section with a diameter, larger than the diameter of the circle inscribed in the cross section of any sector of the wire feed aperture which has a triangular cross section.
2. The contact tip for gas-metal-arc-welding of claim 1 characterized in that the contact tip wire feed aperture comprises three sectors, two of which have a triangular cross section and are located at both tip ends, and the third sector of the aperture occupies the rest middle part of the tip and the said third sector has a circular cross section, while its diameter is larger than the diameters of the circles inscribed in the triangular cross sections of the above said two sectors of the wire feed aperture.
3. The contact tip for gas-metal-arc-welding of claim 1 and claim 2 characterized in that the wire feed aperture of the contact tip comprises four sectors, wherein two of them have triangular cross sections, and the first one is located at the tip front contact end while the second one is located in the middle part of the contact tip, and the wire feed aperture between the said two sectors, together with the wire feed aperture of the tip back receiving end, have a circular cross section with a diameter larger than the diameters of the circles inscribed in the triangular cross sections of the above said two aperture sectors.
4. The contact tip for gas-metal-arc-welding of claim 2 and claim 3 characterized in that related to tips with two sectors with a triangular wire feed aperture, the said sectors have identical cross sections which are equilateral triangles, and the said sectors are rotated with respect to each other around the aperture longitudinal axis at an angle of 60°.
5. The contact tip for gas-metal-arc-welding of claim 1, claim 2, claim 3 and claim 4 characterized in that the tip outside surface, enveloping tip sectors whose aperture cross section is triangular, is shaped as a hexagonal prism with three plane and three curved walls and the prism walls are parallel to the tip longitudinal axis, and the plane walls of the said prism are parallel and equidistant to the corresponding inside walls of the triangular wire feed aperture of the said sectors, while the tip sectors with aperture of circular cross section are enveloped by a cylindrical surface.
6. The contact tip for gas-metal-arc-welding of claim 1, claim 2, claim 3, claim 4 and claim 5 characterized in that related to the sector of the wire feed aperture located at the tip front contact end and having a triangular cross section, the ratio between the diameter of the circle inscribed in the triangular cross section of the said tip sector and the diameter of the wire electrode is 1.15 -1.25.
7. The contact tip for gas-metal-arc-welding of claim 1 characterized in that the tip sector located at the tip front contact end has a triangular aperture, and the surface of the said triangular aperture is helical, white the longitudinal axis of the said triangular aperture coincides with the tip longitudinal axis, and the center of the circle inscribed in the triangular cross section of the said aperture is the cross point of the bisectrixes of the triangle, while the said circle center does not lie on the tip axis.
8.a. The contact tip for gas-metal-arc-welding of claim 7 characterized in that related to wire feed aperture whose surface is helical, the cross section of the said wire feed aperture is an equilateral triangle, and the bisectrix of one of the angles of the said triangle crosses the axis of the contact tip at a point, whose distance to the vertex of the said angle is smaller than the diameter of the wire electrode.
8.b The contact tip for gas-metal-arc-welding of claim 7 characterized in that related to wire feed aperture whose surface is helical and the cross section of the said aperture is triangular, the bisectrix of one of the angles of the said triangular cross section crosses the axis of the contact tip at a point, whose distance to the vertex of the said angle is smaller than the radius of the wire electrode divided by the sinus of half of the said angle.
8.b The contact tip for gas-metal-arc-welding of claim 7 characterized in that related to wire feed aperture whose surface is helical and the cross section of the said aperture is triangular, the bisectrix of one of the angles of the said triangular cross section crosses the axis of the contact tip at a point, whose distance to the vertex of the said angle is smaller than the radius of the wire electrode divided by the sinus of half of the said angle.
9. The contact tip for gas-metal-arc-welding of claims 7 characterized in that related to wire feed aperture with helical surface and with triangular cross section, one of the sides of the said triangular cross section is curvilinear and convex while the other two sides of the said triangular cross section are rectilinear, and the curvilinear side of the said triangular cross section is an arc of a circle, while the diameter of the said circle is larger than the diameter of the wire electrode, wherein the said arc is equidistant to a circle whose diameter is equal to the diameter of the wire electrode, and the said circle tangents the arms of the angle concluded by the said rectilinear sides of the aperture triangular cross section.
10. The contact tip for gas-metal-arc-welding of all above claims characterized in that a sector of the wire feed aperture being located at the tip front contact end having a triangular cross section, is fabricated as a separate insert, and the said insert is pressed in an aperture bored through the tip front contact end or the said insert is threaded to the tip front contact end.
11. A method of fabricating a contact tip far gas-metal-arc-welding of claim 5 is proposed, and the tip includes sectors with triangular wire feed aperture while the outside surface enveloping the said sectors is shaped as a hexagonal prism, and using the said method of tip fabrication, processes of plastic forming - forging or rolling are applied, and the said method comprises:
(A) an initial fabrication stage, in which a cylindrical tubular pre-form of copper or copper alloy, with a passable aperture of circular cross section, is placed in a matrix for forging or the said pre-form is placed in a rolling stand for rolling:
(B) a second stage of plastic forming follows, resulting in the plastic forming of the tubular pre-form or of a sector of the tubular pre-form into a body whose deformed section is a tube with a hexagonal outside enveloping surface and which has a passable wire feed aperture of triangular cross section:
while according to the said method, the said outside enveloping hexagonal surface and the said wire feed aperture with a triangular cross section are obtained simultaneously as a result of the power impact applied by the forming instrument, wherein the said power impact is applied on the outside enveloping surface of the pre-form, only, and the said power impact is directed perpendicularly to the said pre-form axis, while the shape-forming faces of the said instrument (matrix) which contact the pre-form and exercise power impact on it, together with the axes of the rolls of the rolling stand, conclude angles with each other which are equal to the angles of the triangular cross section of the said triangular aperture.
(A) an initial fabrication stage, in which a cylindrical tubular pre-form of copper or copper alloy, with a passable aperture of circular cross section, is placed in a matrix for forging or the said pre-form is placed in a rolling stand for rolling:
(B) a second stage of plastic forming follows, resulting in the plastic forming of the tubular pre-form or of a sector of the tubular pre-form into a body whose deformed section is a tube with a hexagonal outside enveloping surface and which has a passable wire feed aperture of triangular cross section:
while according to the said method, the said outside enveloping hexagonal surface and the said wire feed aperture with a triangular cross section are obtained simultaneously as a result of the power impact applied by the forming instrument, wherein the said power impact is applied on the outside enveloping surface of the pre-form, only, and the said power impact is directed perpendicularly to the said pre-form axis, while the shape-forming faces of the said instrument (matrix) which contact the pre-form and exercise power impact on it, together with the axes of the rolls of the rolling stand, conclude angles with each other which are equal to the angles of the triangular cross section of the said triangular aperture.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2435627 CA2435627A1 (en) | 2003-07-16 | 2003-07-16 | A contact tip for gas-metal-arc-welding |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2435627 CA2435627A1 (en) | 2003-07-16 | 2003-07-16 | A contact tip for gas-metal-arc-welding |
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| Publication Number | Publication Date |
|---|---|
| CA2435627A1 true CA2435627A1 (en) | 2005-01-16 |
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ID=34069914
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2435627 Abandoned CA2435627A1 (en) | 2003-07-16 | 2003-07-16 | A contact tip for gas-metal-arc-welding |
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| CA (1) | CA2435627A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20150048056A1 (en) * | 2010-11-19 | 2015-02-19 | Edward L. Cooper | Welding system and method |
-
2003
- 2003-07-16 CA CA 2435627 patent/CA2435627A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20150048056A1 (en) * | 2010-11-19 | 2015-02-19 | Edward L. Cooper | Welding system and method |
| US10220463B2 (en) * | 2010-11-19 | 2019-03-05 | Edward L. Cooper | Contact tip and weld wire for arc welding |
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