DE1615322C - Process for producing a weld seam with great toughness by means of hidden arc welding - Google Patents

Description

40

The invention relates to a method for producing a weld seam by concealed arc welding, in which two different powder components are arranged separately from one another on the welding joint.

It is known that hidden arc welding uses two main types of welding flux one of which is weakly basic and the other is strongly basic. When using of the weakly basic welding powder, the silicate content of the weld seam increases, which is the so-called large non-metallic inclusion, which causes a decrease in the toughness of the weld seam causes. When acidic slags with a degree of basicity below -0.7 in practice are generated, the toughness of the weld seam decreases sharply. Since it is known to be strongly basic welding powder Are used, the toughness of the weld seam is increased. This peculiarity is in the welding fluxes currently on the market are taken into account. However, this peculiarity is only found in the manufacture of a weld seam applied through several layers at medium Heat generation is produced, whereby the efficiency of the weld is low. One It is not used for automatic welding with high heat generation. This is due to the The fact that the notched impact strength when welding a single layer or a low number of layers. Therefore, in the case of concealed arc welding, a large heat generation, the toughness of the weld seam is not simply increased by increasing the basicity of welding powder can be increased.

It is known from German Auslegeschrift 1116 514 that a powder consisting of SiO ₂ , Al ₂ O ₃ and CaF ₂ can be used to increase the notched impact strength. The notched impact strength is increased by the high fluoride content of the powder. However, no quantitative information is given, and no reference is made to the separation of the fluoride component from the rest of the welding flux.

In U.S. Patent 3,153,719, a submerged arc welding process is used described, in which two different powder components are arranged separately from one another on the weld joint. Any hints how to increase the notched impact strength with the usual welding flux, cannot be found in this patent specification. The present invention has the object based on designing a welding process with a hidden arc in such a way that the notched impact strength the weld seam when welding a single or a small number of visual white layers if possible high is'

Surprisingly, this problem could be solved in principle that on the weld joint two different powder portions are arranged separately from each other, directly on the weld joint a mixture of fluorides and above that a usual neutral or weakly acidic one Welding powder, where the welding takes place with great heat generation.

The method according to the invention for producing a weld seam by concealed arc welding is characterized in that the first welding powder covering the surface of the weld seam a fluoride or mixture of fluorides used in those directly under the arc prevailing temperatures that the first welding powder with a second, neutral or pyrolyzed weakly acidic, usual welding powder is covered, whereby one uses so many fluorides that the slag formed contains a total of 0.13 to 0.35 mol percent fluoride or fluoride mixture and that the degree of basicity of the slag is within the range of -0.50 to +1.25.

In the method according to the invention, a fluoride, for example calcium fluoride, is used as welding powder Magnesium fluoride, aluminum fluoride or a similar compound used at high Temperatures perpendicular under the electric arc is pyrolyzed and fluorine in gaseous form as a first product of a decompensation generated, which is with silicon oxide and silicates in a molten metal connects. After that, the silicon oxide and the silicate evaporate and also generate Metals as a second melting product that has a strong deoxidizing and desulphurising effect shows and recorded separately in the weld joint and from a weakly acidic or neutral welding powder is covered.

The invention is explained in detail below with reference to the figures.

Figs. La, Ib and Ic illustrate the Implementation of the welding process in three different embodiments;

F i g. 2 shows a diagram in which the. Total oxygen content is illustrated in the molten weld versus the molten amount of fluoride with respect to the weld powder;

F i g. 3 shows two diagrams in which the number of non-metallic inclusions against the diameter the non-metallic inclusions is applied;

F i g. 4 shows four diagrams in which the metal content of the weld puddle is illustrated _{against the amount of CaF 2 added.}

Fig. La illustrates the welding process at to which the powdery fluoride has been added separately to the actual welding powder, with a conventional welding powder on which fluoride has been sprinkled. Fig. Ib shows an embodiment in which the fluoride in solid form around the Metal wire is arranged, or the fluoride is enclosed in the steel plate, or an iron pipe is made arranged in the welding joint on which the conventional welding powder is scattered. Fig. Ic Figure 3 illustrates a further embodiment in which the fluoride is externally applied by means of a tube through the upper layer of the welding flux of the welding joint by hand or automatically when welding is fed.

The diagram according to FIG. Fig. 2 illustrates the oxygen content in the puddle in the case of a very tough fine-grained steel, the percentage of fluoride in the enamel with reference to plotted on the welding powder on the ordinate and the total amount of oxygen on the abscissa is.

F i g. 3 illustrates the degree of purity of the weld melt, which was determined by the point counting method [JIS. GO 55]) on a cross section of the weld seam, with the diameter (Viooo ^mm ) of the non-metallic inclusion on the ordinate and the number of non-metallic inclusions Inclusions by counting at each point 'is plotted on the abscissa. F i g. 3 a shows the results in a conventional method, and FIG. 3 b when carrying out the method according to the invention: The diagrams according to FIG. 4 illustrate the metal content of the weld melt in the case of fine-grained, very tough steel, the amount of separately added CaF ₂ (per 200 mm of the weld seam length) being plotted on the ordinate.

In Fig. la is a method of concealed arc welding illustrated with great heat generation, its integral part in the double cover of the weld joint 2 can be seen. This is achieved by having an appropriate Amount of certain compounds (fluorides) which refine the melt flow are scattered on the weld joint 2 which are then usually given a neutral. Welding powder 4 of known type with one high efficiency is covered. The aforementioned purpose of the invention can moreover be achieved by the in FIG. 1 b is applied. This will be Fluoride 3 is applied to the welding wire, or the conventional welding wire is through a replaced by a wire surrounded by a steel tube, in which the wire to be applied to the weld joint 2 Fluoride is included. The conventional welding powder 4 is then sprinkled over this. The The method according to the invention can also be carried out in such a way that, as shown in the figure proceed according to Fig. Ib. The steel pipe is sheathed 6 the fluoride 3 and is automatically fed to the weld joint. With the reference number 1 "is denotes the material to be welded and the reference number 5 denotes the welding wire. In any case it is necessary that the fluoride is added just below the electric arc so that the dissolved products, which are obtained by pyrolysis (decomposition) of the fluoride, are located just below of the electric arc and thus react to the full extent.

Fluorides which are not hygroscopic but which can be pyrolyzed below the electric arc are preferably used, with part of the reaction product being generated in gas form, which displaces the silicon compound from the metal by acting on the silicate compound (large, non-metallic inclusions) in the weld puddle. This creates another part of the product with the deoxidizing effect, and the deoxidized product is made basic. It has been experimentally determined that mixing with more than one fluoride, such as CaF ₂ , MgF ₂ , AlF _2, and the like, gives satisfactory results.

Although the welding powder in concealed arc welding of the known type for wrought iron contains small proportions of certain types of fluoride, the purpose of the additive is to regulate the slag flow and increase the efficiency; because CaF ₂ is mainly used and forms only a few percent. Since the fluorides show only a weak ennobling effect, such a good result can never be expected as with the method according to the invention.

In the method according to the invention, MgF ₂ , CaF ₂ , AlF ₂ , etc. are intensively supplied directly under the single or multiple electric arc, whereby a relatively high density is achieved, and the reaction product and the remaining fluorides are in a composition of Contain slag, which is liquefied together with the welding powder in the upper layer. Therefore, it has been found that the appropriate amount of fluoride to be effective can be determined by the amount of fluoride remaining in the slag. For example, it has been found that in the case of CaF ₂ the amount of about 14 to 25% of the melt flow (in weight of the welding powder) in the upper layer is very favorable, and if this amount exceeds 30% the toughness can decrease again. _{The density of the CaF 2} remaining in the slag under advantageous conditions is between 10 and 20% (0.13 to 0.26 mol percent). When using MgF ₂ , a smaller amount is more favorable. In addition to the direct effect on the function of the fluoride, there is an automatic elimination of superfluous silicates because the oxides in the slag are deoxidized after they have been made liquid with the welding powder in the upper layer. In the conventional process, these excess silicates move into the melt, where they are

cause the formation of harmful silicate compounds. Because the remaining fluoride in relationship are associated with these reactions in the slag and a considerable proportion of the fluoride is lost, a sufficient amount is required in view of the overall success of the process, 'so that the expected effect actually occurs. When the melt flow through the concealed arc. weld is made using the so-called melting welding powder, the Fluorides with these properties are added during welding, a poorer efficiency than the method according to the invention, because it is very clear that the real The proportion of fluoride remaining in the melt flow is greatly reduced. Although a little better effect can be obtained by using welding powder in which the fluoride are mechanically admixed, this effect is also worse than the procedure after method according to the invention because the density of fluorides in the sweat flux as a result of the limitation the efficiency is kept low.

In the following, an explanation will be given of the reason why the weld seam of a single layer or a small number of layers in concealed arc welding with high heat generation using a fluoride and a separately supplied welding powder of the conventional type achieves this high degree of toughness, with on some experimental results are referred to. In the above-mentioned welding process with separately supplied fluoride, the welding joint was _{filled with 20% of the total welding powder with CaF 2} , onto which an almost neutral welding powder of a conventional type was sprinkled. All of the contents of the oxide were made during welding. of a single layer with a concealed arc. The test results are shown in FIG. 2, the total amount of oxygen in the weld seam was reduced more during welding compared to the case in which only conventional welding powder was used. The same results were obtained with the raw steel, a high strength steel and a low temperature tough steel. This is because the fluoride such as CaF ₂ , MgF ₂ and SiF _{2 is} pyrolyzed at a high temperature immediately under the electric arc. A strong oxidizing metal such as Ca, Mg, Al, etc. was generated. These metals have oxidized as a result of the combination with the oxygen present in the welded metal. Microscopic experiments have shown that the degree of purity is higher than that of the weld seam produced by a conventional welding process and that the large inclusion of slag in particular is greatly reduced. In addition, only fine particles are indefinitely shattered according to the examination by the microscope and the electron microscope. This means that the large slag inclusion (A and B type of slag inclusion, which is between 1 and 25 micromillimeters), which is conventionally believed to have adverse effects on mechanical properties, has been reduced in size below 10, and it Numerous slag inclusions below 1 (0.1-0.5) occurred, which were found to be splintered under the microscope. The chemical analysis of the separated non-metallic slag inclusion has shown that the proportions of Si, Fe and S have been greatly reduced, as shown in FIG. 4 is illustrated. This is due to the fact that the gaseous fluorine is generated by the separation of the fluoride into SiO ₂ and other silicate compounds in the weld seam and the SiF ₄ and is separated out of the metal in gaseous form. This shows that O _{2 has combined} with Ca, Mg, etc. and remains in a splintered form in the weld seam as fine CaO and MgO. The ennobling effect is presumably generated primarily by the movement of the melt exactly under the electric arc.

In the following, the reasons will be given why the weld seam is refined and the toughness is improved by the method according to the invention, namely by the main feature that the metal fluoride is fed separately to the weld joint and the welding takes place with a large amount of heat. The first effect is that gaseous fluorine is released vertically under the arc due to the high temperature of the fluoride and _{acts on SiO 2} , whereupon the silicate compound in the weld _{melt evaporates on the one hand as SiF 4} gas and is precipitated from the metal. On the other hand, however, the gaseous fluorine also escapes in various forms of disadvantageous gases (H ₂ H ₂ etc.), which is contained in the weld _{melt together with the SiF 4} gas due to the aforementioned movement of the melt. The second effect is that the highly deoxidizing metal, such as Ca and Mg, by separating the fluoride, on the one hand, strongly deoxidizes the warm molten metal through various types of oxides, and on the other hand, the metals act on the sulfur to prevent its absorption into the slag to facilitate a more stable sulfide.

Since the slag produced during welding _{contains unaffected CaF 2} or HgF ₂ , which with the

. Welding powder of the upper layer is melted together, and since the non-metallic inclusion of slag escapes from the melt, it is necessary that the welding powder connection on the upper layer is well adjusted in order to maintain the basicity for the purpose of the effectiveness of the chemical reaction of this slag at a certain level keep. In practicing the welding method of the present invention, it is desirable that the welding powder used for the top layer be weakly acidic or neutral. In one embodiment of the invention, the welding powder exhibits a weak basicity when it has converted into slag after welding. Concerning the above-described reaction of the welding powder, a similar fact has been observed in the conversion to slag after welding, the welding powder (containing fluoride) being recovered in a water-cooled steel mold after melting. In addition, it is known in this case that the mixture of CaF ₂ and MgF ₂ components is more advantageous than CaF ₂ alone, since something can be saved in the amount used and, moreover, because the notched impact strength can be increased. Because the amount of unconverted fluoride in relation to the physical

Properties, in particular the melting point and the flow properties of the slag produced, it is not desirable that the amount of fluoride retained is particularly large or one certain amount has a short lifespan. The test results have confirmed that that in the process of the invention a conversion of the fluoride content of about 5 to 20% takes place. When determining the fluoride content (the total content), the composition of the Slag after welding, the chemical composition of the weld, the shape of the Oxides, the melting point and the like are taken into account.

Table 1 shows, as an example, an advantageous mixture of a welding powder that is used to achieve a high toughness of the weld seam according to the method according to the invention is particularly suitable. This mixture of fluoride welding powder is fed separately to the welding joint and from the mentioned other welding fluxes.

Table 1

Sweat Group a Group B Group C. powder
Components the mixture 26 to 41 29 to 37 32 to 40 SiO ₂ .... 13 to 24 11 to 22 15 to 30 MnO .... 12 to 35 13 to 22 - CaO .... O to 5 5 to 11 16 to 22 MgO .... 8 to 26 6 to 13 - CaF ₂ .... - 1 to 4 7 to 21 MgF ₂ ... <12 <12 <12 Other ..

A typical example of a mixture of welding powder shows more than one type of compound, which can be FeO, Na ₂ O, K ₂ O, BaO, LiO ₂ , Al ₂ O ₃ , ZrO, etc.

Each component of this composition is provided with a number in the table and is largely used as a conventional welding powder by itself. The common characteristic of this Welding powder consists of basic oxides, acidic oxides and fluorides mixed together and as a whole do not show an extremely acidic or extremely basic character.

The above-mentioned basicity was calculated by the following formula, and a basicity of -0.5 to +1.25 of the slag is appropriate for the ingredients given in Table 1; h. that their Values approximate from neutrality to weakly basic character.

B _L (basicity) = Σ aiNi,
wherein

Ni: mole of the corresponding oxide,

ai: a constant indicative of the oxide used.

example

1 _L = +4.80 (mol of the MnO in percent)
+ 6.05 (mol of CaO in percent)
+4.00 (mol of the MgO in percent)
+ 3.40FeC

-6.31 (mol of SiO ₂ in percent)
-4.97 TiO.
-0.20Al ₂ O ₃

With reference to the composition of the core wire used in the method according to the invention Is used, there is no specific requirement, and the conventional types of materials can find use with a satisfactory effect, especially welding wires with a Mo content suitable for improving toughness.

In the following an explanation of the test results regarding the chemical constituents and the basicity of the slag is given, the test results using samples with a 2 mm V-notch of the weld seam at ⁰ ° C. to determine the "Charpy" values , and also the oxide content of the weld seam, the change in the chemical constituents of the separate non-metallic slag inclusions and the like in the concealed arc welding of different types of steel when welding only one layer with high heat generation, whereby the welding wires were replaced, the welding conditions changed and the welding powder modified became. In addition, the chemical components of the weld seam and the changes in the results of the impact tests at temperatures between 0 and -17 ° C were determined when the welding process mentioned is used with two concealed arc electrodes. Also the test result regarding the constituents of the welding powder, the generation of the slag, the slag. itself, the chemical composition of the weld seam, the notched impact tests with the samples mentioned at temperatures from 0 to -20 ° C, etc.

was laid down, the aforementioned welding _{method being used for welding with Co 2} gas, and these test results are summarized below.
Table 2 shows the types of steel used in the tests, the symbols, the wall thicknesses of the steel plates and the chemical composition. Table 3 shows the conventional welding wires used in the experiments, the symbols for the composition of the wires and the results of the chemical analysis of the welding wires. In the tables, IN steel is a fine-grain steel with aluminum nitride components.

In addition, the welding conditions (welding process, shapes and angles of the welding joint, Voltage and amperage, welding speed and the number of layers) in table 4 specified.

209 643/195

9 10

Table 2 (number 1)

Test steel and its chemical composition (%)

Type of steel

Wall C. Mn Si P. · ■ s symbol strength
the plate mm 0.13 1.33 0.30 0.011 0.021 IN-A 25th 0.10 1.12 0.24 0.011 0.013 IN-B 35 0.16 1.23 0.35 0.020 0.013 IN-C 25th 0.11 1.00 0.27 0.013 0.014 IN-D 25th 0.094 0.75 0.24 0.019 0.009 IN-80 20th 0.10 1.27 0.28 0.015 0.005 FLT ■ 25 0.14 1.36 0.40 0.015 0.017 SM 50 35

Al
all in all

IN steel (40kg)

IN steel (40 kg).

IN steel (50kg)

IN steel (50kg)

1 N steel (HY 80)

Aluminum nitride with steel

(for low temperature) high-strength steel

(50kg)

0.071 0.095 0.097 0.057 0.064

Table 2 (number 2) test steel and its chemical composition (%

Type of steel

symbol

Wall Al Al ₂ O ₃ • AlN N Ni - strength
the plate Sol. Cr mm . 0.064 0.014 0.040 0.015 25th 0.091 0.007 0.037 0.011 35 0.086 0.020 0.036 0.015 25th 0.050 0.013 0.034 0.015 25th 0.060 0.007 0.057 0.022 2.51 20th 0.036 0.005 0.011 0.29 25th 35

IN steel (40kg)

IN steel (40kg)

1 N steel (50kg)

IN steel (50kg)

1 N steel (HY 80)

Aluminum nitride with steel

(for low temperature) high strength steel

(50 kg)

IN-A IN-B IN-C IN-D IN-80

FLT SM

Table 3 Chemical composition of the welding wire (%)

Conventional material used symbol
of the wire C. Mn Si P. S. Mon For concealed arc welding. W-A 0.06 0.65 0.03 0.012 . 0.010 - ' For concealed arc welding. W-B 0.07 0.75 0.01 0.50 For concealed arc welding. W-C - 0.10 1.00 0.02 0.012 0.013 ■ -. For concealed arc welding. W-D 0.12 1.50 0.02 0.013 0.020 - For concealed arc welding. W-E 0.08 1.50 0.04 0.011 0.015 0.50 For concealed arc welding. W-F. o; o8 1.00 0.30 0.008 0.013 - For CO ₂ gas arc welding .... W-G 0.12 1.08 0.51

Table 4
Summary of the welding conditions

Welding process Weld joint Symbol of Sweat Sweat Sweat
speed number conditions voltage electricity age of the locations (Shape, size) (Volt) (Amp.) (cm / min) Concealed arc 60 °, V, 10 m / m depth C-A 37 to 39 900 33 1 Concealed arc 70 °, V, 10 m / m depth C-B 38 850 35 1 . Double covert 60 °, V, 20 m / m depth C-C 41 1000 40 1 Electric arc CO ₂ arc 60 °, V, 20 m / m depth CD 38 500 30th 1

Table 8

Notched impact strength of the weld seam in a single layer (group 2 welding flux)

Welding powder Cover
powder Generated Slag Sweat steel Sweat Weld metal Mon
(%) 2mm V-notch with several fluorides F-C wire condition 0.60 Charpy value separated
supplied fluoride F-C symbol B _L W-B IN-C C-A symbol 0.60 (kgm / cm ² )
0 ⁰ C F-C s-1 -0.54 W-B IN-C C-A N-I 0.60 10.6 CaF _2, 5 g F-C S-2 + 0.65 W-B IN-C C-A N-2 ' 0.60 11.7 CaF ₂ , 10 g F-C S-3 +0.93 W-B IN-C C-A N-3 0.60 13.5. CaF ₂ , 15 g F-C S-4 + 1.13 W-B IN-C C-A N-4 0.60 15.8 CaF ₂ , 20 g F-C S-5 + 1.05 W-B IN-C C-A N-5 0.50 16.2 CaF ₂ , 25 g F-C S-6 +0.63 W-A IN-C C-A N-6 0.50 11.0 MgF _2, 4 g F-C S-20 +0.64 W-A IN-C C-A N-20 0.50 9.0 MgF _2, 8 g F-C S-21 +0.82 W-A IN-C C-A N-21 0.50 15.7 MgF ₂ , 12 g F-C S-22 +0.81 W-A IN-C C-A N-22 0.50 17.0 MgF ₂ , 16 g S-23 + 0.73 W-A IN-C C-A N-23 13.2 MgF ₂ , 20 g S-24 +0.72 N-24 10.3

The amount of separately supplied fluoride is given by the amount required for one weld seam length of 200 mm is required.

Table 9 shows the basicity and the chemical composition of the slag during welding.

Table 10 shows the chemical composition of the weld seam using a welding powder of group 2.

Table 9

Welding powder < "luorids the fluoride components and the chemical components SiO ₂ MnO CaO CaF ₂ MgO MgF ₂ Al ₂ O ₃ the slag FeO Bl Welding powder des '. Cover symbol Welding powder powder the
generated 37 17th 17th 9 • 4 - 2 TiO ₂ 3 -0.54 fed separately F-C slag 33 17th 25th 9 4th - 2 3 +0.65 - ' F-C S-I 31 16 26th 13th 4th - 2 3 2 + 0.93 CaF _2, 5 g F-C S-2 29 15th 27 16 4th - 2 3 2 + 1.13 CaF ₂ , 10 g F-C S-3 27 14th 25th 20th 3 - 2 3 2. + 1.05 CaF ₂ , 15 g F-C S-4 26th 13th 22nd 26th 5 - 2 3 2 + 0.63 CaF ₂ , 20 g F-C S-5 33 20th 19th 10 '7 - 3 3 4th +0.64 CaF ₂ , 25 g F-C S-6 32 18th 19th 10 9 2 2 3 5 +0.82 MgF _2, 4 g F-C S-20 31 16 18th 9 9 "3 2 3 6th + 0.81 MgF _2, 8 g F-C - S-21 30th 14th 18th 9 10 9 2 3 5 + 0.73. MgF ₂ , 12 g F-C S-22 29 13th 17th 8th 10 12th 2 3 5 +0.72 MgF ₂ , 16 g F-C .S-23 3 ' MgF ₂ , 20 g S-24 3

Table 10

Chemical composition of the weld metal (group 2 welding flux)

symbol C. Mn Si P. S. Mon Al
all in all Al ■
pure AI ₂ O ₃ AlN N · of
Sweat
metals 0.10 1.30 '0.35 0.018 0.013 0.60 0.170 0.140 0.054 0.001 0.014 N-I 0.10 1.25 0.33 0.018 0.014 0.60 0.042 0.022 0.038 0.001 0.014 N-2 0.10 1.28 0.31 0.017 0.013 0.60 0.067 0.035 0.060 0.001 0.014 N-3 0.10 1.25 0.29 0.018 0.014 0.60 0.080 0.045 0.066 0.001 0.014 N-4 0.10 1.25 0.29 0.018 0.014 0.60 0.045 0.011 0.065 0.001 '0.014 N-5

The constituents of the mixture of different welding fluxes that are used as a top layer over the fluorides and the basicity of the components are given in Table 5 below.

Table 5.

_; Chemical composition of welding powder (%)

group symbol SiO ₂ MnO CaO CaF ₂ MgO MgF ₂ Al ₂ O ₃ TiO ₂ FeO B _L Group 1 FA 30th - 30th - 20th 10 + 2.08 .F-B 42 15th 25th - 7th - 2 5 - -0.08 Group 2 F-C 37 19th 18th 10 4th - 2 3 2 -0.36 F-D 37 17th 15th 6th 14th - - - 2 +0.37 Group 3 F-E 12th 13th - - 4th - 4th 27 30th -0.40

The following Table 6 shows the chemical constituents and the basicity B _{L of} the slag when using a conventional welding powder of group 1.

Table 7 shows the results of the impact tests with the 2mmV notched Charpy specimens of the weld at 0 ⁰ C, wherein a welding powder of the group 1 and the fluoride CaF _2, fed separately in amounts of from 15 to 25%, was used.

Table 6

Composition of the slag made using a welding powder with a larger number

was generated by fluorides

(In this case Group 1 welding fluxes were used)

Produced slag + 2.14 SiO ₂ MnO CaO CaF ₂ MgO MgF ₂ Al ₂ O ₃ TiO ₂ FeO symbol +0.22 S-A 30th 32 12th 18th · 3 - 1 S-B 35 11th 26th 11th 4th - 2 3 6th

Table 7

Notched impact strength of the weld seam in a single layer (In this case, Group 1 powders were used)

Welding powder
with several fluorides

tested
ίβΙ

mixed fluorides

Produced slag

symbol

welding wire

steel plate

Welding condition

Weld metal

Mon
symbol

2mm V-notch
Charpy value

(kgm / cm ² )
'O ⁰ C

FA
FA
FB
FB

CaF ₂ , 15%
CaF ₂ , 15%
CaF ₂ , 25%
CaF ₂ , 25%

SA
SA
SB
SB

+ 2.14
+ 2.14
+ 0.22
+0.22

WA
WA
WA
WA

IN-C
IN-C
IN-C
IN-C

CA
CA
CA
CA

Tue
D-2
D-3

0.50
0.50

, 1.4

1.3

7.8

11.5

As the tables show, the Charpy values of the weld, which produced a slag with a basicity of +2.14, are as low as with conventional welding flux, regardless of whether the welding wire contains Mo or not, and the addition of CaF ₂ had no effect at all. But when using a welding powder, which produces a slag having basicity of +0.22, the Charpy values increase at 0 ⁰ C from 7.8 to 11.5 kgm / cm ^2, regardless of how the composition of the Welding wire is chosen, although the same amount of the same type of fluoride was used. This result shows that a welding powder whose slag is neutral or weakly basic can be used well in the method according to the invention. It is therefore important to choose a welding flux with adequate basicity for surface transformation. Further, Table 8 shows that when a Group 2 welding powder such as FC powder whose basicity is -0.36 is used, the notch toughness value increases to more than 10 kgm / cm ² when the basicity of the slag is separated The addition of fluorides assumes values between -0.54 and +1.13, and even 16 kgm / cm ^{2 are achieved} with increasing addition. The same tendency can be observed _{when using MgF 2.} The notched impact strength value increases from 12 to 17 kgm / cm ² with a lower addition of MgF ₂ compared to the use of CaF ₂ .

This experiment also shows that the basicity of the slag produced is about -0.36 is effective in the method according to the invention.

continuation

symbol C. Mn • Si • 0.30 P. S. Mon Al Al Al ₂ O ₃ AlN N of 0.34 all in all pure Sweat
metals 0.10 1.25 0.30 0.019 0.014 0.60 0.044 0.009 0.065 . 0.001 0.014 N-6 0.09 1.07 0.29 0.017 0.013 0.50 0.034 0.015 - 0.037 0.001 0.011 N-20 0.09 1.05 0.28 0.015 0.012 0.50 0.041 0.011 0.057 0.002 0.010 'N-21 0.09 1.02 0.29 0.017 0.012 0.50 _v 0.033 0.007 0.039 0.002 0.010 N-22 0.09 0.99 0.015 0.013 0.50 0.031 0.006 0.044 0.002 0.009 N-23 0.09 1.02 0.019 0.012 0.50 0.042 0.014 0.054 0.001 0.012 N-24

The result of the analysis according to the "Activac" method (neutron irradiation method) of the total content of oxygen in the weld seam, which was produced by the method according to the invention using conventional steel, shows aluminum nitrides contained in the steel and a value of 50 kg / mm ² fine-grain steel when using a welding powder of group 2 (basicity +0.37), and here a welding wire of conventional type, which is shown in Table 11, was used. The result shows that the oxide content in the weld seam is lower than in the case of using CaF ₂ and MgF ₂ in comparison with the cases in which a separate supply was not carried out, which proves that the welding method according to the invention is used to reduce the oxide content the weld seam is more effective than the known methods.

Table 11

Total content of oxygen in the weld metal (%)
(Group 2 welding flux)

Welding powder rr
in connection
Welding powder
fed separately lit fluorides
manure
Welding powder
for the
conversion welding wire Welding condition Wrought iron Wrought iron with
Aluminum nitride
Weld metal
(FL T 2) ■ · 0.043 *) IN steel
Weld metal
(IN-C) F-D W-A C-A 0.074 0.063 0.070 F-D W-A C-A 0.072 *) CaF ₂ , 10 g
4th F-D W-A C-A CaF ₂ , 17.5 g F-D W-A. C-A 0.056 *) CaF ₂ , 25 g F-D W-A C-A 0.051 0.045. MgF _2, 6 g F-D W-A C-A 0.038 *) 0.050 *) MgF ₂ , 12 g F-D W-A C-A MgF ₂ , 20 g 0.047 *). 0.058 0.050 0.049 0.047 *) 0.044 *)

*) In the lower columns means that the Mo content is 0.50%.

Table 12 shows the result of chemical analysis of the weld in the case of using a welding powder with a basicity of +0.37 and in the case of separately supplying CaF ₂ on which the same powder is scattered. :,:

17 18

Table 12 Chemical composition of weld metal (%)

symbol C. Mn Si • P S. Mon Al
total AI
pure Al ₂ O ₃ Mg Ti Approx N of
Sweat
metals 0.11 1.22 0.35 0.018 0.013 - 0.034 0.023 0.022 0.006 0.003 0.001 0.013 M 54 0.10 1.20 0.36 0.017 0.013 0.50 0.043 0.031 0.024 0.006 0.003 0.001 0.013 M 55 0.12 1.11 0.28 0.018 0.013 - 0.027 0.008 0.037 0.003 0.002 0.001 0.012 M 52 0.11 1.11 0.30 0.018 0.013 0.50 0.029 0.006 0.042 0.007 0.004 0.001 0.012 M 53

Table 13 shows the result of chemical analysis of the nonmetal inclusion produced by the material of Weld was separated by the electrolytic separation process.

table

Result of the chemical analysis of the non-metal inclusion in the weld metal (By electrolytic separation process) (Group 2 welding flux)

Welding powder with fluorides Sweat Sweat steel Sweat
öcdin ~ S. Mon
(%) Al Mn Si S. Fe Mon C. powder wire plate supply Weld metal - to the 0.50 separate Around ■ - Fluoride supply Wall
lung 0.50 0.019 0.007 0.007 0.008 0.038 0.016 F-D W-A IN-C C-A symbol 0.022 0.007 0.010 0.012 0.024 0.008 0.057 - F-D W-A IN-C C-A M 54 0.033 0.005 0.001 0.001 0.019 0.002 0.057 - F-D W-A IN-C C-A M 55 0.031 0.005 0.004 0.003 0.007 0.001 0.097 CaF ₂ , 17.5 g F-D W-A IN-C C-A M 52 CaF ₂ , 17.5 g M 53

This result clearly shows that the silicon content, which is the main component in the large metallic inclusion, is small, thus proving that the silicate compound is small, and hence the total amount of oxygen is also small. It is evident that, as already mentioned, the fluoride _{results from the decomposition of the CaF 2} or MgF ₂ , with silicon or silicate compounds being separated and exiting in gaseous form. be precipitated from the metal.

The experimental results summarized in Table 14 will now be discussed, with for the purpose of

the comparison once only a fluoride together with the welding powder according to group 2 and for others have used more than one species.

In each case, the basicity of the slag was approximately +0.73 to +1.13, and the results of the Charpy notch impact tests were carried out again with the V-shaped 2 mm notch made from a material of the weld seam at temperatures of 0 ^° C . Values of 12.6 to 20.2 kgm / cm ^{2 were} achieved here, and it is also apparent from this that a good result is obtained even when several types are used.

table

Notched impact strength of the weld seam in a single weld layer (Group 2 welding powder together with fluorides)

. ":]
Sch
symbol ) through the e
white process
MgF ₂
(Mol
percent) according to the invention
sn generated Sc
CaF ₂
(Mol
percent) ße "
ilacke
B _L
I. Sweat
wire steel Sweat
condition symbol metal
Mon 2mm V-notch
Charpy 'value
(kgm / cm ² )
- o ° c S-IOO 0.06 0.13 + 0.81 W-A IN-A C-A T-60 0.25 17.1 S-105 0.04 ■ 0.13 +0.82 W-A IN-A C-A T-66 0.25 15.2 S-115 - 0.23 + 1.13 W-F IN-A C-A T-17 0.25 13.7 S-105 0.04 0.13 -. +0.82 W-E IN-A C-A T-64 0.20 15.3 Silo 0.02 0.13 +0.64 W-E IN-A C-A T-40 0.20 20.2

MgF ₂ CaF ₂ B ₁ . 1 61 steel Sweat 20th ι Weld metal Mon 2mm V-notch (Mol (Mol condition (%), Charpy value percent) percent) + 1.13 15 322 0.20 _ '0.23 +0.73 IN-A 0.12 (kgm / cm ² ) 0.08 0.13 + 1.05 continuation IN-A C-A symbol - O ⁰ C -. 0.31 + 1.13 IN-A C-A 0.25 15.4 ■ - 0.23 + 1.13 IN-A C-A T-36 0.25 13.4 19th .— 0.23. Sweat IN-A C-A T-24 13.3 wire C-A T-27 12.6 T-29 13.7 T-89 W-F By the invention W-F Welding process produced slag W-D W-A W-D symbol S-115 S-120 S-125. S-115 S-115

The following table 15 shows the Charpy values of the weld seam material at 0 ^° C., the basicity of the slag when welding steel being mixed with a mechanical mixture according to group 2 and MgF ₂ and CaF ₂ . It was found that in this case the values of the slag are all between 15 and 18 kgm / cm ² .

Table 15

Notched impact strength of the weld metal in a single layer
(When welding forged steel)

Produced slag MgF ₂ CaF ₂ ^b l Sweat steel Sweat Weld metal ° 2mm V-notch (Mol (Mol wire material condition (%) Charpy value in the method according to the invention percent) percent) + 1.13 —— - 0.23 + 0.81 symbol - (kgm / cm ² ) 0.06 0.13 + 0.95 W-A FLT C-A - 0 ⁰ C symbol - 0.27 +0.95 W-A FLT C-A R-31 0.50 15.4 - 0.27 WC- SM 50 C-A R-42 18.3 S-115 WC SM 50 C-A R-62 15.4 S-IOO R-63 16.2 S-130 S-130

As is illustrated in the following Table 16, with a basicity of the slag of +0.82 and the mentioned 2 mm V-notch, Charpy values of 4.8 kgm / cm ² at -75 ° C. are achieved when a high-toughness and high-strength steel is welded. The fact that this value can be achieved at such a low temperature shows how this welding process works.

Table 1'6

Notched impact strength of a single weld
(High-strength IN steel)

Produced slag
B _L welding wire steel Welding condition Sweat
symbol metal
Mon
(%) 2mm V-notch
Charpy value
(kgm / cm ² ) ■
-75 ⁰ C + 0.82 W-B ■ IN-80. C-B H 20 0.70 4.8 ..- ■ '

The result of a corresponding test with two concealed arc wires is summarized in Tables 17 and 18. If the basicity of the slag is similarly kept at about 0.23, notched impact values of the weld seam material of 15.9 kgm / cm ² at 0 ° C and 13.4 kgm / cm ² at -17 ° C are also achieved. Table 18 shows the result of chemical analysis of the weld material.

Table 17

Notched impact strength of the weld metal of a single weld layer, which is achieved by means of
a double concealed arc (tandem system) was established

Generated
slag
.: ■ ' B _L welding wire steel Sweat
condition Schweil
symbol !metal
Mon
(%) 2mm V-notch
O ⁰ C
(kgm / cm ² ) - Charpy value "
-17 ° C
(kgm / cm ² ). +0.23 W-E IN-B C-C A-19 0.21 15.9 13.4

Table 18

• 22

Chemical composition of a weld metal in double hidden arc welding

(Tandem system) (values in%)

Symbol of
Sweat
metals C. Mn Si P. S. Mon ■ Al
total Al
alone Al ₂ O ₃ AlN N A-19 0.09 1.50 0.29 0.016 0.015 0.21 0.055 0.031 0.044 0.002 0.012

The welding method according to the invention can also be applied to carbon dioxide welding, and the result is exactly the same as mentioned above. This can be seen in Table 19, which shows the basicity of the slag produced in the arc under CO ₂ , the fluoride exhibiting a basicity of about -0.40 with the addition of CaF ₂ and MgF ₂ , and the Charpy- Values with the 2-mm-V-notch at 0 and -20 ⁰ C were determined. In this case, the Charpy values ⁰ C and 11.1 to 14.9 kg m / cm ² at 2O showed 13.4 to 21.3 kg m / cm ² at ⁰ ° C.

. Table 19

Notched impact strength of the metal welded in a single layer by means of the CO _{2 arc}

Welding powder
with several fluorides mixed fluorides Produced slag -0.26 Sweat steel Sweat Weld metal Mon 2mm V-notch
Charpy value -20 ⁰ C
(kgm / cm ² ) Sweat
powder CaF ₂ , 13% symbol wire IN-B condition symbol 0.12 O ⁰ C
(kgm / cm ² ) 11.1. F-E CaF ₂ , 13% S-30 WC IN-B C-C D-118 0.33 13.6 11.2 F-E CaF ₂ , 13% S-31 W-E IN-B C-C D-28 - ' 13.4 - - F-E CaF ₂ , 13% S-32 W-F IN-B C-C D-80 0.12 15.7 - F-E CaF ₂ , 13% S-33 -0.05 W-F IN-B C-C D-81 0.24 21.3 -. F-E MgF ₂ , 15% S-34 .W-F IN-B C-C D-85 0.12 17.0 12.5 F-E MgF ₂ , 15% S-35 WC IN-B C-C D-124 0.12 16.2 14.4 F-E MgF ₂ , 15% S-36 W-D IN-B C-C D-IOl 0.12 15.0 14.9 F-E MgF ₂ /15% S-37 W-F IN-B C-C D-133 0.12. 17.0 - F-E S-38 W-F C-C D-82 19.2 One · ·.* melt - IN-B - 13.2 «© F-E S-39 W-F C-C D-137 15.6

The following Table 20 shows the basicity, the chemical composition, etc. of the slag generated _{in the CO 2 arc.}

Table 20
Chemical composition of the _{slag generated in the CO 2} arc (%)

Welding powder

Welding powder
with several fluorides

Welding powder

mixed
Fluoride

Symbols

the

generated slag

TiO ₂

Al ₂ O ₃

MnO

CaO

CaF ₂

MgO

MgF ₂

B _L

FE
FE

CaF ₂ , 13%
MgF ₂ , 15%

S-30 S-35

27 30 29

4 18 12

13 17 18

10

11th

-0.40 -0.26 -0.05

Table 21 shows the chemical analysis of the metal of the weld.

Table 21
Chemical composition of the weld seam in a CO ₂ arc

Symbol of
Sweat
metals C. Mn Si P. S. Mon Ti Al
total AI
alone AlN N D-118
D-28
D-80 0.08
0.09 1.21
1.53 0.36
0.71 0.010
0.009 0.016
0.017 - 0.022
0.023 0.026
0.029 0.010
0.004 0.005
0.006 0.012
0.013

Claims (6)

Patent claims: 1. Process for producing a weld seam by concealed arc welding, in which two different powder components are arranged separately from each other on the welding joint, characterized in that one the first welding powder covering the surface of the weld seam is a fluoride or a Mixture of fluorides used at the temperatures directly under the arc pyrolyzed that the first welding powder with a second, neutral or weak acidic, usual welding powder is covered, using so much fluoride that the slag formed contains a total of 0.13 to 0.35 mol percent fluoride or fluoride mixture, and that the degree of basicity of the slag is within the range of -0.50 to +1.25. 2. The method according to claim 1, characterized in that the fluoride or fluoride mixture used is continuously fed through a pipe during welding. 3. The method according to claim 1, characterized in that the fluoride or fluoride mixture used in a manner known per se in solid form around a core wire in the weld joint is arranged. 4. The method according to claim 3, characterized in that the fluoride or fluoride mixture is introduced into the weld joint in a hose-like sheathed form. 5. The method according to claim 1, characterized in that it is under an argon, helium or Carbon dioxide atmosphere is carried out. 6. The method according to claim 1, characterized in that a double hidden arc is used.