QUICK RELEASE AND CONTACT AREA MIG DEFLECTING POINT BACKGROUND OF THE INVENTION 1. Field of the invention. The present invention relates to electric welding, and in particular to a device incorporated in the welding gun of cable welding machines. 2. Description of the prior art. In the welding of metals in inert gases (mig for its acronym in English) the contact tip of the gun must perform satisfactorily two important functions. First, you must precisely guide the electrode to the contact point of the workpiece. Second, you must conduct the appropriate current, which can be up to 400 amps and more, to the electrode. To achieve these results, it is known that a relatively long copper contact tip must be provided, and that it has an axial hole along it. The hole has a size slightly larger than the diameter of the electrode. The contact tip extends from a gas diffuser through which an inert gas is directed around the welding electric arc. The current to the contact tip is supplied by the gas diffuser. The contact tips are particularly subject to at least two failure modes. The first is that it can burn, which occurs if the supply of the electrode through the contact tip is interrupted while maintaining an electric arc. The second failure mode is longitudinal hole fatigue due to the abrasive nature of the electrode material. In addition, because the contact tip is so close to the electric arc, and because the tip must conduct strong electric currents, it gets very hot. High temperatures also have a harmful effect on the contact tip, in part because the more heated the tip the more it softens, which makes it less resistant to the wear produced by the electrode. Due to the severe operating conditions, the contact tips have relatively short service lives. Consequently, they are treated in the industry as consumable items. Typically, the contact tips are made as separate pieces that are placed in the gas diffusers. When a weathered contact tip is removed from the gas diffuser and discarded, a new one is screwed into place. As noted above, in addition to the heat caused by the electric arc, another potential source of heat for the contact tip are the cords between it and the gas diffuser. That is, the rope can cause resistance heating. To minimize electrical resistance, the contact tip and the strings of the gas diffuser have a relatively long joint length and a thin diameter. A typical rope for pre-contact tips and gas diffusers is .250-28 UNF with approximately .25 inches of axial joint between the two pieces. However, the long-bore thin diameter rope presents a problem. Removing a used contact tip from the gas diffuser requires several turns of the contact tip. For example, with 28 rope turns, seven turns are required to produce .25 inches of axial movement for removal. If the electrode burned and melted with the contact tip, the electrode should be twisted the same number of turns as the contact tip. The potential jump of the contact tip completely removed, due to the twisted electrode, is annoying, if not potentially dangerous. In addition, the time required to disassemble the multiple turns also contributes to downtime of the production area. U.S. Patents 5,338,917 and 5,440,100 show a welding gun wherein a gas diffuser has a projection to contact a channel of variable width at the contact tip. When installed together, the contact tip and the gas diffuser come into contact with each other at one point and on two lines. The total area of contact at the point and on the lines is extremely small, thereby increasing the resistance heating produced by the welding current. U.S. Patent 2,761,049 shows a soldering gun with a contact tip received and held by a cap nut in an elongated guide tube. There is a frusto-conical junction surface between the contact tip and the guide tube. The contact tip and the cap nut are surrounded by a gas rate that is slidable on the guide tube. Replacing the contact tip requires sliding the gas rate and turning the cap nut several turns, both to remove the contact tip and to install a new one. Since the cap nut is a separate and removable part, it is subject to loss or damage. U.S. Patent 2,808,498 shows an electrode contact tip driven into a welding gun. The electrode emerges from the welding gun through a ceramic nozzle tip that is screwed into a cooling jacket. The replacement of the contact tip requires a complicated process of disassembly and reassembly of the welding gun. Accordingly, there is a need for improvements in the contact tips and gas diffusers of the electrode welding machines. SUMMARY OF THE INVENTION In accordance with the present invention, a quick-release gun contact tip ig is provided which minimizes resistance heating between the contact tip and a gas diffuser. This is achieved by manufacturing the contact tip and the gas diffuser with frusto-conical surfaces that are joined simultaneously and with adapter cords, or any other quick connect and disconnect device. The upstream end of the gas diffuser can be constructed in such a way that it can be adapted to any desired welding gun handle. The various ports and passages for the shielding gas can also take any shape you desire. The downstream end of the gas diffuser is made with a frusto-conical interior surface with its apex towards the upstream end of the gas diffuser. In the embodiment that uses adapter ropes for the quick disconnect connection, the base end of the frusto-conical surface ends in an adapter cord having little more than a single turn of rope. The adapter string ends at the downstream edge of the gas diffuser. The downstream end of the contact tip may be conventional. The downstream end is formed with a frusto-conical outer surface of the same bevel and diameters as the frusto-conical surface of the gas diffuser. The base end of the frusto-conical surface of the contact tip ends in an adapter cord that is equal to that of the gas diffuser. The adapter cord of the contact tip has approximately a single turn of active rope. With the contact tip assembled to the gas diffuser, the entire area of the frusto-conical surface of the two pieces are in intimate frontal contact with each other. In addition, the joined areas of the strings of the two pieces are in frontal contact. The large areas of contact between the two pieces allow them to handle intense currents with minimal resistance heating. Likewise, it only takes a single turn in reverse of the contact tip to remove the gas diffuser when replacement is required. According to another aspect of the invention, the contact tip is manufactured, very economically, polygonal raw material. The raw material is extruded with an external hexagonal or similar surface and with the hole for the electrode. The downstream end of the contact tip is rotated slightly to a cylindrical surface, leaving a portion of the hexagonal surface to be handled with keys. Adapter cords are rotated to the desired diameter that is greater than the transverse distance of the hexagon, and the flat portions of the frusto-conical outer surface are rotated at the upstream end from the hexagonal surface. The method and device of the invention, using frusto-conical mating surfaces and adapter strings, thus conduct strong currents without excessive heating. The adapter ropes conduct a significant portion of the current, even though they allow the contact tip to be removed and replaced in the gas diffuser with a single turn. Other advantages, benefits and features of the present invention will be apparent to those skilled in the art upon reading the detailed description of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an enlarged perspective view of a typical electrode welding gun that includes the present invention. Figure 2 is a side view of the gas diffuser of the present invention. Figure 3 is a transverse and longitudinal view of the gas diffuser of Figure 2. Figure 4 is a side view on an enlarged scale of the contact tip of the invention. Figure 5 is a side view of a modified embodiment of the contact tip. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Although the present disclosure is detailed and accurate, to enable those skilled in the art to practice the invention, the physical embodiments disclosed by the present merely exemplify the invention, which may have modalities in other specific structures. The scope of the invention is defined in the claims appended hereto. Referring to Figure 1, a typical soldering gun 1 including the present invention is illustrated. The particular electrode welding gun 1 shown is merely representative of a wide variety of guns that can advantageously utilize the invention. The gun has a handle 3 which is attached at one end to a gas diffuser 5. A contact tip 7 is screwed into the other end of the gas diffuser 5. A nozzle 9, which is generally adjustable to the gas diffuser, surrounds to the gas diffuser and most of the contact tip 7. A long, flexible electrode 11 is fed to the handle 3 and to the gas diffuser, and out of the contact tip. Electric power is supplied to the gun 1 by wires represented by the reference number 13. The energy is conducted to the contact tip 7 by the gas diffuser 5, and from the contact tip to the electrode 11. In accordance with this invention, the gas diffuser 5 and the contact tip 7 are designed to provide a rapid release therebetween, as long as they conduct maximum current to the electrode 11. In one embodiment, a balloonboard connection is used in combination with friable mating surfaces. conical In the embodiment shown in Figures 2-4, the gas diffuser is generally tubular in shape, with an upstream end 14, a downstream end 17 and an axial passage 19. The internal cords 15 extend in the axial passage 19 from the upstream end 14. The ropes 15 are joined with similar ropes from the handle of the gun 3. The radial holes 21 pass through the wall of the gas diffuser from the axial passage. The axial passage 19 includes a plug hole 22 near its downstream end 17. An internal adapter string 23 is applied to the plug hole 22. I discovered that the bayonet adapter string .313-14 works very well. Preferably, the adapter rope 23 has approximately 1.5 turns of rope. The plug hole 22 ends at the base end of a frusto-conical internal surface 25 which is also part of the axial passage 19. The apex end of the frusto-conical surface 25 is located in the vicinity of the radial holes 21. It works very well. well an included angle of approximately 10 ° for the interior frusto-conical surface. The contact tip 7 has an upstream end 27 and a downstream end 29. A hole 37 extends axially through the interior of the contact tip along its entire length. The contact tip defines an external frusto-conical surface 31 at the upstream end 27 which has the same bevel and diameters as the frusto-conical internal surface of the gas diffuser 25. At the base end of the frusto-conical surface of the contact point there is a cylindrical surface 32 with a diameter slightly smaller than the diameter of the plug hole of the gas diffuser 22. The cylindrical surface 32 terminates in an external adapter string 33. The adapter cord of the contact tip 33 has the same diameter and cords that the adapter cord of the gas diffuser 23. A working end 35 of the contact tip 7 extends from the adapter cord 33 to the downstream end 29. The working end 35 may have a cylindrical surface as shown in the drawing, a frustoconical surface, or a combination of cylindrical and frustoconical surfaces. If desired, flat surfaces for keys, which are not shown, can be formed at the working end of the cylindrical version. The gas diffuser 5 and the contact tip 7 are used when screwing permanently the strings 15 of the gas diffuser to the corresponding strings of the handle of the gun 3. The frusto-conical surface 31 of the contact tip is inserted in the plug hole 22 and the frusto-conical surface 25 the gas diffuser until the cords of the contact tip 33 come into contact with the strings of the gas diffuser 23. The initial angular orientation between the contact tip and the diffuser of Gas is relatively unimportant. The tip of contacts then rotated until the outer adapter string of this is attached to the internal adapter cord of the gas diffuser. The contact tip is rotated until its frusto-conical surface comes into contact with the frusto-conical surface of the gas diffuser. The adapter ropes and frusto-conical surfaces of the two parts have such dimensions that the two frusto-conical surfaces are joined approximately after one turn of the contact tip in the gas diffuser, after their strings were initially joined, and before the adapter cord of the contact tip reaches the end of the adapter cord of the gas diffuser. That is, the adapter cord of the contact tip has approximately one turn of active cord, and the screwing of the contact tip in the gas diffuser is limited by the contact between the frusto-conical surfaces, and not by the cord the contact tip that reaches the end of the rope of the gas diffuser. With the contact tip 7 assembled to the gas diffuser 5, the electrode 11 can be fed through the passage of the gas diffuser 19 and the hole of the contact tip 37. A considerable current can be conducted to the electrode by the diffusing gas and tip of contact, due to the large contact area between the two pieces that supply the matching frusto-conical surfaces 25 and 31. The adapter strings 23 and 33 provide a significant additional contact area. Consequently, heating by resistance in and between the parts during the operation of the gun 1 is minimal. When it is necessary to remove a used contact tip 7, a single reverse turn is sufficient to free it from the gas diffuser 5. Therefore the torsion of the burned electrode 11 in the contact tip is limited to a single turn. The axial movement corresponding to the single turn of the contact tip is approximately only .07 inches. Similarly, a new contact tip is assembled to the gas diffuser with a single turn. The entire replacement process is accomplished with very little downtime. Yet another advantage of the tip of the gun of the invention is its increased resistance, when measured by low-rope stretches, of the bayonet adapter strings 23 and 33 compared to the previous UNF cords. This reduces the possibility of damage to the adapter cords during the replacement process. An unexpected benefit of the acme adapter strings 23 and 33 attached to the matching frusto-conical surfaces 25 and 31 is the increased torque retention they provide between the contact tip 7 and the gas diffuser 5 compared to the previous quick release designs . The possibility of the contact tip being dislodged from the gas diffuser during welding operations is reduced in this way. Likewise, the heating and cooling cycles inherent to the welding process can cause permanent interference between the UNF matching strings of the previous designs. This problem does not exist in the design of adapter ropes of the present invention. Likewise, and in accordance with the present invention, in a modality the tip of contact lends itself to be manufactured through an economic process. Now turning our attention to FIG. 5, a contact tip 39 is manufactured from an extrusion section of copper material with a hexagonal periphery 41 and a longitudinal hole 37 '. The work end of the contact tip 39 is rotated to a cylindrical surface 43, leaving a portion of the hexagonal periphery 41 as flat surfaces for keys. The adapter cords 33 'are rotated from the smallest hexagonal periphery to the diameter of .313 inches of the cords. The frusto-conical surface 31 'is also rotated from the hexagonal periphery. The design of the contact tip 29 allows the greatest economy for the size of the raw material. Accordingly, it is apparent that, in accordance with the invention, a quick-release mig welding gun tip with increased contact area fully satisfying the objectives and advantages stipulated above was provided. While the invention was described in conjunction with specific embodiments thereof, it is clear to those skilled in the art that many alternatives, modifications and variations are apparent in light of the foregoing description. For example, a bayonet connection can be used instead of adapter cords for the quick release tip. Accordingly, it is intended to cover all these alternatives, modifications and variations that remain within the spirit and broad scope of the appended claims.