DE1558891B2 - Welding wire containing additives and a process for its production - Google Patents

Description

The invention relates to a welding wire containing additives for automatic and semi-automatic Gas-shielded welding in which the additive is in powder form inside a tubular Metal body is arranged. The invention also relates to a method for producing this Welding wire.

A known composite welding wire of this type (US Pat. No. 29 09 778) is intended for outdoor welding, ie without protective gas, in which case the molten metal is covered by slag. This means that the powdery additive has a large amount of slagging agent. In contrast, however, the invention is concerned with a welding wire containing additive for welding with the supply of protective gas, such as, for example, CO ₂ .

In the case of the previously known welding wire, it is also provided that the flux is used with the additive provided welding wire contains, in addition to the arc stabilizer and the deoxidizer also add slagging agents. It is also known that the slagging agents and the previously used arc stabilizers usually made of inorganic compounds, for example metal oxides, metal carbonates or metal fluorides exist. These substances form a top layer of slag over the weld seam during the welding process and guarantee consequently a clean seam formation. However, it is disadvantageous that before a subsequent Welding process the slag top layer must first be removed. This removal of the Slag top layer is extremely cumbersome and time consuming, and very often requires more than that Half the time it takes for the entire welding process. This will increase the economy welding is greatly reduced.

It is also known to use solid welding wires in automatic welding processes under protective gas as well as welding wires containing additives and having complicated cross-sectional shapes. However, due to various disadvantages, these wires have not yet been widely used found. The massive welding wire can be manufactured at relatively low cost and for that Use mild steel for welding because it contains special alloying elements when welding in the composition of the welding wire is not required. When welding special steels, For example, high-strength and low-alloy steels, it is necessary in the welding wire to provide certain alloy additives, the type and amount of which depends on the composition of the depend on the steel to be welded. The manufacture of such a welding wire with a core consequently turns out to be very expensive, especially when the wire is drawn.

The known welding wires also depend on which material is to be welded impaired in their workability. There are no funds when using solid welding wire known, through which the arc can be stabilized. The welding process therefore often suffers from the so-called "spraying", in which large drops of molten metal disrupt the welding process, give the machined surface of the workpiece an unsightly appearance and an uneven, cause rough weld seam, so that the application of the solid welding wire on a very small GS area is limited.

The disadvantages of the solid welding wire are admittedly due to the use of an additive Welding wire, the inside of which is filled with flux, avoided. The manufacture of such However, welding wires are expensive because of their complicated shape, and it can be with these Welding wires do not fall below a certain limit diameter.

A disadvantage of the known additives containing welding wires, which adversely affects the operation lies in the fact that the arc cannot be precisely concentrated, since these conduct the electrical current.

The cross-sectional area of the wire is small in relation to the outer diameter of the wire. because for this reason, a large amount of current cannot be concentrated at one point, the workpiece becomes Melted relatively flat compared to solid welding wires and thus the welding quality degraded.

From all of this it follows that in the manufacture of such a welding wire the additive and the distribution of which must be given extraordinary great attention and the achievement of it a good surface of the wire requires a very closely monitored production and quality control. Namely, the influence of the unevenness in the surface state of the welding wire is remarkable great. This applies in particular to welding wires with a smaller diameter, for example in of the order of less than 1.6 mm. Uneven surface texture makes in these cases very often an effective welding process is impossible at all. It has therefore become natural to divide the known welding wires into two classes according to their surface properties, namely in the class of copper-clad welding wires and in the class of those with oxide layers coated welding wires.

Solid welding wire can be copper-clad; Welding wire containing additives can be opened Do not plate because of its powder content. The "baking" of oxide layers is therefore exclusively used in the manufacture of welding wires with an additive.

Welding wires are copper-clad for two reasons: On the one hand, the surface of the Welding wire are protected from rust, which degrades the welding quality extremely strongly; on the other hand, good conductivity should be maintained on the electrode holder for the supply of electrical power will. If the copper plating is satisfactory, the stated aim can be fully achieved. However, it is extremely difficult technically and economically to obtain a satisfactory one Copper plating. For this purpose, namely the surface of the welding material must be kept completely clean before plating. If this is not the case, it will not just be the purpose the copper plating is missed, but there is a risk that the plating during the welding process flakes off or is pushed off. If scraped copper splinters come between the tip, clamp tight and interrupt the welding process. Overall, that also makes it more expensive Copper plating the production of welding wires due to the necessary equipment.

The formation of rust should also be prevented by baking on oxide layers. With this one Method is by baking at a certain temperature and for a certain period of time a thin oxide layer is formed on the wire that has already been drawn with the required diameter. The baking temperature is usually 350 to 400 ° C. Another Purpose pursued, namely the removal of contaminating substances, for example fat, which in the Wire production inevitably occur on the wire surface. Baking will also removes the moisture from the powdery additive of the welding wire. The oxide layer Although it fulfills the task of rust prevention on the wire surface. However, theirs is disadvantageous low electrical conductivity. This disadvantage does not apply to welding wire with a diameter of more than 2 mm not noticeable in weight. However, if welding wire diameters of less than 1.6 mm are used come, the low electrical conductivity noticeably affects the welding process, often even makes welding impossible. Man

ίο leads back to the fact that the oxide layer with the The lead in the electrode holder is connected and the power is supplied via the oxide layer. Since this has a higher electrical resistance than the metal, it occurs within the layer Heat, which can cause the temperatures to rise to such an extent that the holder and welding wire are partially melted will. As a result, the electrical resistance is temporarily increased, so that due to this unevenness in the supply of electrical energy results in an unstable arc and consequently result in a welding process that is difficult to control. When the melting of the electrode holder and the welding wire becomes too strong, the supplied welding wire even kinks the feed rollers, so that the welding process is interrupted. This buckling also occurs particularly easily with small diameter welding wire.

The invention is therefore based on the object of creating a welding wire with additives and a method for producing this welding wire, which can be produced as easily and simply as normal hollow wire without copper plating, even with very small diameters, for example below 1.6 mm. This welding wire should be able to be subjected to the baking process without the disadvantageous effects described and should be usable for higher currents than before.
The features of the welding wire according to the invention, created to solve this problem, result from claim 1. Advantageous embodiments of this welding wire are listed in claims 2 to 4.

The term "powder additive" used here broadly denotes both

.,. very fine powder as well as larger particles, regardless of the uniformity of the particle distribution.

Contains the arc stabilizer provided in the welding additive according to the invention at least graphite, also aluminum and / or titanium. These additives can not only be elementary, but also in the form of alloys with one another or with iron. The deoxidizer can be one or more of the additives manganese, silicon, titanium and aluminum, usually in the form of iron alloys. There are therefore the additive of the invention Welding wire aluminum and / or titanium as an arc stabilizer or deoxidizer used.

The welding consumable used does not contain a slag-forming agent, as usually does Flux is added during welding. On the other hand, it may be advantageous to add the additive to add certain alloy components to the composition of the particular to be welded Adapt the workpiece. It's also under

In some circumstances it is advisable to add iron dust to the melting effect during welding raise.

In the welding wire according to the invention, the cross-sectional area of the additive, the consists of the mixture of arc stabilizer and deoxidizer, on the order of magnitude held from only 5 to 25% of the total cross-section of the welding wire. That means that the Wall thickness of the metal body with a ratio of 75 to 95% is very large. This will take Among other things, the conductivity for the electric current, i.e. the permissible limit current density, is remarkable elevated. Therefore, the welding wire according to the invention can be compared to that mentioned at the beginning use previously known welding wire at very high current densities. This in turn results a very good arc concentration and a very good depth effect during the melting process. the Formation of the metal body, which is available for the power line, with a cross-sectional portion of 75% and above gives the welding wire according to the invention properties that make it known Makes welding wires superior and has not yet been observed on any known welding wire are.

Due to the exclusion of slag-generating additives in the additive used in the inventive Welding wire is included, and due to the use of graphite as an arc stabilizer instead of the known alkali metal oxides, the product according to the invention is used Welding wire except for a very small amount of the oxidation product due to the deoxidizer no slag. The required removal of the slag in a subsequent The welding process is therefore omitted.

The amount of arc stabilizer should be about 2 to 10 percent by weight and the amount of Deoxidizing agents are 20 to 90 percent by weight, based on the total weight of the additive. The weight of the arc stabilizer is in relation to the deoxidizer normally not more than 20 ° / o. the total of both.

The method according to the invention for producing the welding wire results from claim 5.

The fact that the wire before drawing, so before the final shape, a temperature of exposed to a maximum of 350 ° C and then the baked raw wire at least three times is pulled, there is a great advantage. This increases the surface quality of the wire exceptionally well.

The invention is explained in more detail below with reference to the drawing. These show in

F i g. 1 to 3 cross-sections through different embodiments of welding wires according to the invention,

Fig. 4 is a diagram showing the permissible current densities when welding,

F i g. 5 shows a diagram of the melting depth as a function of the current when using the Welding wire in the automatic welding process.

F i g. 6 schematically in a block diagram the manufacturing process and

F i g. 7 shows the individual shape stages in the production of the welding wire according to the invention.

In the simplest embodiment of the welding wire according to FIG. 1 contains a hollow metal body 2, a powdery additive 1. Since it is difficult to make the metal body 2 cylindrical in advance To shape, this is usually made from a metal strip that is around its longitudinal axis is bent. A joint 3 therefore arises in the longitudinal direction of the metal body 2.

In the embodiment of the metal body 2 according to Figure 2, the outside of the joint 3 is to

ίο creating a seal 4 welded. Through this For example, the surface can be treated in a plating process. At the same time becomes effective prevents moisture from penetrating the inside of the welding wire.

In the embodiment according to FIG. 3, the metal body 2 is formed from an outer part 2 b and an inner part 2 α . This shape facilitates the production of the metal body 2.

In an actual test, two types A and B of welding wires with filler were made, each 1.6 mm in diameter. The metal bodies of the two wires A and B were made of mild steel; the interior of the metal bodies was filled with powdery additive 1 of the composition shown in Table 1.

Table 1

Fe - Mn

, - Fe - Si

Fe-Ti

graphite

Iron powder

Aspect ratio
Powder to total cross-section

A I B
(Weight percent)

57

24

15th

10

18th
6th
4th
1

71

24

In addition to the two wires A and B , another welding wire C was produced with additives of the known type and used as a control sample.

The permissible current density of each of these wires is shown in Fig. 4. The welding tests were carried out _{under CO 2 protective gas.} The test results are shown in Table 2, where the welding speeds under different welding conditions (such as current strength, etc.) on the welding wires A and B are compared with the results obtained with the known welding wire C with a diameter of 3.2 mm.

6o 300 Tabel 2 )
450 500 78.9
77.5
47.0 350 Current (A
400
(cm / min 138.0
140.1
83.4 168.0
168.2
104.7 65
Wire A ..
Wire ...
WireC .. 96.2
96.0
56.4 115.0
115.2
69.8

In further comparative tests, the meltdown depth during the welding process was compared using the three welding wire types A, B and C at different current intensities. The achieved here, from F i g. 5 apparent results make the superiority of the welding wire according to the invention over the known welding wire clear.

As shown in FIG. 6 schematically illustrated process steps for producing the welding wire can be seen, the thin metal strip 2 is bent in a molding process I and at the same time the powdered additive 1 is poured in, so that a shaped raw wire is formed. The molding process I This is followed by a further forming process II, in which the metal strip 2 becomes a circular Cross-section is bent further until it reaches the figure shown in FIG. 7 reached the last form shown. In this condition the powder filling in the raw wire is not sufficiently compacted to allow the additive to move 1 to prevent within the metal body 2 during the subsequent treatment and the uniform Ensure training of the wire. It also prevents one on the outside of the metal body 2 adhesive layer of dirt and grease and the moisture contained in additive 1 the Application of the wire in this condition. For this reason, another molding process is completed III, in which the raw wire to compress the additive 1 and to achieve the desired Shaping the wire is drawn in relation to the required diameter by draw forming. Before however, the raw wire is baked immediately after the forming process I. The baking process removed the layer of dirt and grease adhering to the metal body 2 and evaporates the in the additive 1 contained moisture. The baking process is carried out at a temperature of 180 to 350 ° C.

The baking process immediately following the molding process I results in the following Advantages:

1. Because of the still low density of the powdered additive within the wire blank, the removal of the dirt and "fat layer ⁴⁵ on the metal body and the humidity in the additive by the heat treatment is very simple.

2. Due to the low baking temperatures, an oxide layer arises compared to the usual oxide layers very thin oxide layer, which then becomes even thinner through the subsequent drawing steps. This will make the electrical Significantly improved conductivity.

Table 3

55

The last-mentioned advantage is particularly serious, which is why it is particularly significant proves the thickness of the oxide layer formed during the baking process in the following drawing processes, in which the oxide layer becomes thinner. Extensive tests have shown that the oxide layer is best kept under control when the baking temperature is at most 350 ° C. Table 3 shows the effects of different baking temperatures on the drawing process and the welding quality.

Baking temperature Drawability Sweat
Results
(Grade
according to JIS) Not baked
180 to 200 ° C
230 to 250 ° C
270 to 300 ° C
310 to 340 ° C
350 to 380 ° C Well
Well
Well
Well
a bit difficult
not drawable 6th
4th
1
1
1

The welding wires used in the tests had a design according to FIG. 1. The raw wire had a diameter of 3.4 mm and contained powdery additive which was composed of 17% iron dust, 18% FeMn, 6% FeSi, 4% FeTi and 1 ° / o consisted of graphite. This raw wire was drawn to a diameter of 1.2 mm after baking. The welding wire obtained in this way was used in the welding tests at an amperage of 300 A and a voltage of 28 V (DCRP) and an inflow of 20 l / min of CO ₂ shielding gas. From these experiments it can be deduced that a baking temperature in the range from 200 to 350 ° C. is very suitable. A temperature below 200 ° C is not sufficient to remove the layer of dirt and grease. A temperature above 350 ° C creates an oxide layer that is too thick, which causes the wire to tear off in the subsequent drawing step. In contrast, an oxide layer generated in a temperature range of 250 to 350 ° C not only prevents the wire from tearing off, but also refines the oxide layer and thus increases the electrical conductivity with each subsequent drawing step. In addition, the refinement of the oxide layer increases the protection against corrosion. The number of drawing processes has a significant influence on the quality of the wire. The raw wire is therefore drawn at least three times after baking. Table 4 shows the relationship between the electrical conductivity and the number of drawing processes.

Table 4

Dependency of the electrical conductivity
on the number of pulls

number
the By Electrical conductivity i ability
Current- No. Pulling knife Welding conditions strength-
swan- (mm) kungen 1 1 3.0 500 A -38 V 25 A 2 2 2.6 400A-34V 23 A 3 3 2.2 35OA -32V 15 A 4th 4th 2.0 300 A-30 V 1OA 5 6th 1.6 250A-28V 8A 6th 7th 1.4 170 A - 26 V 1OA 7th 8th 1.2 100 A-24 V 1OA

The wires used in these tests contained additives of the same composition as that used for the tests according to Table 3. The wires were pulled one to eight times after the baking process, which took place at a temperature of 270 to 300 ^° C.

509517/292

Has been performed for an hour. The voltage and amperage used were dependent adhered to by the wire diameter. A constant voltage direct current source was used as the power source used. The current fluctuations during the welding tests were measured by means of an ammeter read to determine the electrical conductivity. The smallest emerged Fluctuations if the welding wire was pulled at least three times in a row. These The tendency corresponds to the degree of stability during the welding process. Because a power surge of the order of 15 A is considered permissible during the welding process three pulls will be considered sufficient for good weld quality.

Table 5 shows results obtained in tests under the conditions similar to Table 4 became. One exception is that the wires used are not after the first form pre- ao rather, after the last drawing process, they were baked at a temperature of 270 to 300 ° C.

Table 5

number
the By Electrical conduct ε ability
Current- No. Pulling
geese knife Welding conditions strength-
swan- (mm) kungen 11th 1 3.0 500 A -38 V 25 A 12th 2 2.6 400 A -34 V 25 A 13th 3 2.2 350A-32V 2OA 14th 4th 2.0 300 A-30 V 2OA 15th 6th 1.6 250 A - 28 V 28 A 16 7th 1.4 170 A -26 V 26 A 17th 8th 1.2 100 A - 24 V. 30A

A comparison of the results of Tables 4 and 5 shows that Runs 1 and 11, 2 and 12, etc. noticeably differ from each other. That is clearly due to the different procedures used by the two Test series traced back. In particular, the greater the current intensity fluctuation falls with increasing Number of drawing steps in table 5, compared to the one in the table. 4 a much cheaper one There is a tendency.

The improvement in the anti-corrosive property by baking the raw wire was among the Conditions according to Table 6 tested.

Table 6

Test conditions
Baking the raw wire

Number of pulls

Diameter (mm)

Sample # 1
270 to 300 ° C

5
1.6

Sample # 2

5
1.6

Both samples were under the same environmental conditions (temperature 30 ° C, relative Humidity 85 ° / o) kept. The degree of rusting was compared in both samples. After 72 hours, a noticeable rust formation could be observed with the naked eye in the case of sample no. while the surface of Sample No. 1 showed no change. After 144 hours Reddish rust covered the entire surface of Sample No. 2 while on the surface of the sample No. 1 only rust spots were noticed.

For this purpose 2 sheets of drawings

Claims (5)

Patent claims: 1. Welding wire containing additives for automatic and semi-automatic inert gas welding, in which the additive is in powder form inside a tubular metal body is arranged, characterized in that the metal body (2), which the highly compressed additive (1) in powder form in It encloses the longitudinal direction, is so thick-walled that the cross-sectional area of the additive, based on the total cross-sectional area of the welding wire, is only 5 to 25%, whereby the Welding additive made from a mixture of arc stabilizer and deoxidizer and the arc stabilizer contains graphite. 2. Welding wire according to claim 1, characterized in that that the welding consumable (1) as an arc stabilizer and deoxidizer Contains aluminum and / or titanium. 3. Welding wire according to claim 1 or 2, characterized in that the amounts of the arc stabilizing agent and the deoxidizing agent, based on the total weight of the additive (1), 2 to 10% or 20 to 90% be. 4. Welding wire according to one of claims 1 to 3, characterized in that the metal body (2a, 2b ) is of multi-part cylindrical design. 5. A method for producing the welding wire according to one of claims 1 to 4, wherein a baking process is carried out to produce an oxide layer on the outer skin of the welding wire, characterized in that flat material is bent transversely and the powdered additive is introduced, then the flat material is completely bent over the powdery additive is closed, then the baking process is performed at a temperature of 180 to 35O ⁰ C and finally, the thus prepared raw wire is brought by at least three times drawing through a drawing mold to the desired diameter.