JP2005224816A - Tig welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high speed TIG (Tungsten Inert-Gas) welding method with which heating with a welding arc only to the welding center part can be performed by preventing the diffusion of the welding arc heat and an undercut is not generated when the high speed TIG welding to a thin aluminum sheet is performed without using a backing material. <P>SOLUTION: The aluminum having the chemical composition composed by wt% of ≤0.11% silicon, 1.15-1.35% iron, ≤0.01% copper, 0.40-0.60% manganese, ≤0.003% magnesium, ≤0.01% chromium, ≤0.02% zinc, ≤0.03% titanium and ≤0.05% individual component and ≤0.15% total content of the other component content except aluminum and the balance aluminum, is formed as a sheet-state or a foil-state having 0.1-1.2 mm thickness, and ≥5 m/min welding speed and 105-135 ampere welding current value are applied. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a TIG welding (TIG welding) method using aluminum having a specific chemical component.

  Aluminum has high ductility and good workability, and pure aluminum is often used as a constituent material of various composite materials, and composite pipes of polyethylene and aluminum are also used in the piping field for water and hot water. This composite pipe can be bent at the pipe construction site, and the raw material aluminum used is a pure aluminum sheet or foil with a thickness of 1.2 mm or less that is relatively soft and has a high ductility. . When this pipe is welded and extended, since aluminum is thin, butt welding is usually performed by TIG welding.

  TIG welding is welding performed in an inert gas atmosphere such as helium or argon, and is performed using tungsten or a tungsten alloy which is not easily consumed as an electrode. It is widely used for welding non-ferrous metals and alloy steels, and has good arc stability even at low currents, making it suitable for welding thin objects and first-layer welding of pipes.

  However, when TIG welding is performed on a thin aluminum plate without using a backing material, especially when welding continuously at a high speed of 5 m / min or more, the thermal conductivity of aluminum is high, so the arc during welding The heat generated by the heat spreads and escapes, the welded part tends to become low temperature, and it is difficult to keep heating the butted portion of the weld to the necessary and sufficient temperature.

  FIG. 1 shows the relationship between the welding speed and the welding current value when TIG welding is performed on thin aluminum. If the welding current value (I, horizontal axis) is small relative to the welding speed (V, vertical axis), the amount of heat generated by the arc is insufficient, resulting in insufficient penetration of the welded portion (see (a) in the figure), and the current value (I). ) Is too large, it melts away due to overmelting (see (c) in the figure). In addition, when the welding speed (V) is high, if an excessive current is applied, an undercut tends to occur (see (d) in the figure) (for example, see Non-Patent Document 1). 2A, 2B, 2C, and 2D show the connection points corresponding to FIGS. 1A, 1B, 1C, and 1D.

  Thus, if the welding current value is increased in order to compensate for the amount of heat that diffuses, the center of the weld is overheated, and an undercut is likely to occur in the weld. Undercut refers to the occurrence of an undercut beat as a result of the molten pool being pushed down by an arc pressure based on a large current, and the grooves formed on both sides of the undercut beat significantly reduce the strength of the welded plate. . Therefore, the portion has a low strength and may become a fatal defect.

Table 4 shows chemical components of an ordinary pure aluminum (JIS H4000 A1100, hereinafter simply referred to as pure aluminum) plate. In such a pure aluminum plate, if the thickness is larger than 1.2 mm, TIG welding can be performed even at a welding speed of 115 amperes to 135 amperes at a welding speed of 5 m / min or higher. Although it is possible, if the thickness is 1.2 mm or less, at a high speed of 5 m / min or more, if the welding current value is less than 115 amperes, the amount of arc heat is insufficient and welding cannot be performed. There is a problem that undercut occurs and induces the destruction of the welded portion, and welding is virtually impossible.
The Japan Welding Association edition "Basics and Practice of the New TIG Welding Method" First Edition Sangyo Publishing Co., Ltd. Published October 20, 1992 Pages 43-44

  The problem to be solved by the invention is that when high-speed TIG welding is performed on a thin aluminum plate without using a backing material, diffusion of the welding arc heat is prevented, and heating by the welding arc only in the welding center is enabled. The object is to provide a high-speed TIG welding method that does not cause an undercut.

  In order to achieve the above object, the TIG welding method (Invention 1) according to claim 1 of the present invention has a chemical component of silicon content of 0.11% by weight or less, iron content of 1.15% by weight to 1.%. 35% by weight, copper content of 0.01% by weight or less, manganese content of 0.40% by weight to 0.60% by weight, magnesium content of 0.003% by weight or less, chromium content of 0.01% by weight or less, zinc Content of 0.02% by weight or less, titanium content of 0.03% by weight or less, other components other than aluminum are individually 0.05% by weight or less, and the total content is 0.15% by weight or less. The aluminum is a plate or foil having a thickness of 0.1 to 1.2 mm, and is welded at a welding speed of 5 m / min or more and a welding current value of 105 to 135 amps.

  Table 1 shows chemical components of aluminum used in the TIG welding method of the present invention. These chemical component numerical values are the results of analysis of chemical components by the method defined in JIS H 1306 (Atom Absorption Analysis Method for Aluminum and Aluminum Alloy).

  When a thin pure aluminum plate having a thickness of 1.2 mm or less is TIG welded at a high speed of 5 m / min or more, the weldability deteriorates if the silicon content in the chemical composition of the aluminum plate is large. In the aluminum of Invention 1, the silicon content is 0.11% by weight or less. In addition, although the minimum is not defined, it may be the same as the amount contained in so-called pure aluminum.

  Furthermore, if the iron content is 1.15% by weight or more, the arc concentration increases, but if it exceeds 1.35% by weight, the ductility of aluminum decreases. Therefore, the iron content is 1.15 wt% to 1.35 wt%.

  The content of copper is generally an element that lowers the weldability, and is therefore ½ (0.01% by weight) or less of the content contained in pure aluminum.

  The content of manganese is related to the strength of the material, and as the content increases, the strength becomes too high and the flexibility expected of aluminum is impaired, so it is almost the same as the content contained in pure aluminum. Same or less (0.40 wt%).

  When magnesium is contained, it tends to increase the stress corrosion cracking property, so the content is 0.003% by weight or less.

  The chromium content is related to the strength of the material, and if it is contained, it has the effect of increasing the strength and impairing the flexibility expected of aluminum, so it is 0.01% by weight or less.

  The zinc content has the effect of improving weldability, but has a tendency to lower the corrosion resistance, so the upper limit is made 2.5 times or less the content contained in pure aluminum.

  The content of titanium is related to the strength of the material, and has an effect that the flexibility expected from aluminum is impaired due to excessively high strength.

  Other chemical components have little influence on important characteristics such as weldability and strength, and do not affect the welding speed and the welding current value during TIG welding, and therefore may be the same as the content contained in pure aluminum.

  In the present invention, by using aluminum containing the above-mentioned specific chemical component as aluminum, a plate-like or foil-like aluminum having a thickness of 0.1 mm to 1.2 mm can be obtained at a welding speed of 5 m / min or more and a welding current. It becomes possible to weld at a value of 105 amperes to 135 amperes.

  That is, for example, in the case of a thick aluminum plate having a thickness of about 1.2 mm, if the welding current value is about 135 amperes, welding can be performed at a welding speed of about 5 m / min. In the case of a thin aluminum plate of about 1 mm, TIG welding can be performed without overmelting if the welding speed is increased to about 17 m / min or the welding current value is decreased to about 105 amperes.

  In any case, the welding current value can be welded even at a low current value of about 105 amperes where pure aluminum can not be welded when the welding speed exceeds 5 m / min, and about 135 amperes. Even with a high current value, it is possible to perform welding without overmelting by adjusting the welding metal temperature.

  In the TIG welding of the present invention, by using aluminum having an iron content in a predetermined range as the aluminum, the arc is concentrated at the time of welding even when the welding current is a low current value, and the welding portion is heated to the temperature. Is less likely to decrease, and since the current value is small, the arc pressure is low and undercut is unlikely to occur. Moreover, if iron content exists in the said range, the ductility of aluminum will not fall. Furthermore, since a predetermined upper limit is provided for the silicon content, cracks are unlikely to occur in the welded portion. Therefore, if aluminum of the above chemical component is used, TIG welding can be performed at a high speed by adjusting the welding current value even if the aluminum is thin.

  Next, an example of TIG welding of an aluminum plate having the chemical component of the present invention is shown. As shown in Table 2, if this aluminum has the same thickness, the tensile elongation rate according to JIS Z 2241 (metal material tensile test method) is about 1.times. About 5% larger.

(Example 1)
Among the chemical components of the present invention, aluminum having an iron content of 1.15 wt% to 1.35 wt% and the content of other components in the range described in Table 1 is used as a foil having a thickness of 0.45 mm. A composite pipe having a pipe wall in which both surfaces are laminated with cross-linked polyethylene was prepared. This composite pipe was butt-connected by a normal composite pipe connection method. That is, the pipe end faces of the two composite pipes to be connected were butted together, the aluminum foils in contact with each other were TIG welded, and the polyethylene layer was repaired after welding.

  Table 3 shows TIG welding conditions. That is, the welding speed was 17 m / min, and the welding current value was changed from 105 amperes to 135 amperes in increments of 5 amperes. No backing material was used.

  After completion of TIG welding, the composite pipe was subjected to a fracture hydraulic pressure test. The results are also shown in Table 3. In the table, the weld failure rate is a visual judgment of whether the failure starting point is a weld or a place other than a weld location, and if there is a failure from other than a weld location, there is no weld failure. did.

(Comparative Example 1)
For comparison with Example 1, except that aluminum was aluminum in which the iron content was 0.85 to 1.15% by weight and the content of other components was in the range shown in Table 1. A composite pipe was prepared in the same manner as in Example 1, and this was similarly TIG welded. After the end of TIG welding, the composite pipe was subjected to a fracture hydraulic pressure test. The results are also shown in Table 3.

(Comparative Example 2)
Further, for comparison, a composite pipe was prepared in the same manner as in Example 1 except that aluminum was changed to pure aluminum described in Table 7, and this was similarly TIG welded. After the end of TIG welding, the composite pipe was subjected to a fracture hydraulic pressure test. The results are also shown in Table 3.

  Aluminum thin plates are often used in the IT industry and the like, but high productivity is required in these industrial fields to perform high-quality welding at high speed. Therefore, if the properties other than the welding performance of aluminum used in the present invention satisfy the properties required by the application, it can be used as a method for realizing high productivity.

It is a graph which shows typically the relationship between the welding speed in the case of TIG welding thin aluminum, and a welding current value. FIG. 1 schematically shows the state of a welding point in each of the areas A to D in FIG. 1, (a) is a cross-sectional view of an undermelted area, (b) is a cross-sectional view of a normal bead area, and (c) is an overmelted area Sectional drawing of an area | region, (d) is sectional drawing of the area | region where an undercut generate | occur | produces.

Explanation of symbols

A Area of insufficient melting B Area of normal bead C Area of overmelting D Area where undercut occurs 1 Aluminum plate 2 Molten aluminum

Claims (1)

Chemical components are silicon content 0.11 wt% or less, iron content 1.15 wt% to 1.35 wt%, copper content 0.01 wt% or less, manganese content 0.40 wt% to 0.00. 60% by weight, magnesium content 0.003% by weight or less, chromium content 0.01% by weight or less, zinc content 0.02% by weight or less, titanium content 0.03% by weight or less, other components other than aluminum Aluminum with an amount of 0.05% by weight or less and a total content of 0.15% by weight or less, and the balance being aluminum, is formed into a plate or foil with a thickness of 0.1 mm to 1.2 mm, and a welding speed of 5 m. TIG welding method characterized by welding at a welding current value of 105 amperes to 135 amperes per minute / minute.

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