CN1102480C - Process for manufacturing welding wire - Google Patents

Abstract

A seamless flux core suitable for welding high strength steel and steel structures subject to high restraints, with a diameter of 0.8 to 4mm, which has excellent crack resistance and primer protection qualities and contains very little diffusible hydrogen Welding wire, the process of manufacturing by dehydrogenation treatment with high temperature heating includes the steps of: by direct electric heating through first and second pair of roller electrodes arranged at a distance of 2 to 5 m and through a toroidal transformer arranged between them, Heat a straight welding wire with a diameter of 8 to 15mm to a temperature between 620 and 1100°C; cool the heated wire with a heat transfer coefficient not higher than 250kcal/m ² h°C (≈214.98W/(m ² ·K)) to no higher than 500°C; and stretched to the desired diameter. The weldment formed from the wire thus obtained contains not more than 5ml of diffusible hydrogen per 100g of deposited metal.

Description

Wire Manufacturing Process

The invention relates to a process for manufacturing flux-cored welding wire for low-hydrogen welding. The welding wire has high crack resistance and primer protection quality, and is suitable for welding high-strength steel and other high-quality steels and steel structures that withstand large binding forces .

The dehydrogenation treatment in the seamless flux-cored wire manufacturing process is generally carried out as follows: heat the tubular flux-cored wire stretched from 10 to 13 mm in diameter to 2 to 4 mm in a bell furnace or tunnel arch furnace to 600 to 800 ℃. Heat dehydrogenation is used for small diameter wires from 2 to 4 mm for the following reasons: (1) there is no effective heat dehydrogenation process for larger diameter wires; and (2) small diameter wires tend to coil or Ring, which is required to shorten the overall length of bell furnaces or tunnel arch furnaces.

In addition, the hardness of the skin must be controlled to meet the filling ratio and other technical conditions of each flux-cored wire, so as to ensure good wire feeding efficiency of 0.8 to 4mm diameter wire during automatic welding and prevent wire breakage during manufacturing. Then, the diameter of the welding wire to be heated must be determined by taking into account the work hardening of the skin which occurs when the welding wire is stretched after softening annealing. Thus, one heating can serve two different purposes, dehydrogenation and softening of the skin. In addition, the commonly used bell furnace and tunnel arch furnace are not completely satisfactory, because the productivity of the bell furnace is low and the thermal efficiency of the tunnel arch furnace is low, and the material, structure and service life of the tunnel arch furnace do not allow high Used at temperatures of 800°C and they require a large installation space.

As automatic welding has become popular, the use of bare wire and flux-cored wire has also increased, while flux-cored wire with seam skins constitutes the mainstream. Since 100g of deposited metal produces approximately 7ml of diffusible hydrogen, this wire has an undesirable tendency to form hydrogen-induced cracks in welding of high strength steels or in steel structures subjected to high restraint forces. When used to weld primed steel, wires containing too much hydrogen have a tendency to form air voids, shrinkage cavities, and other weld defects.

The reason why it is difficult to manufacture a low-hydrogen welding wire with a seam skin is as follows: (1) The filled flux contains binding moisture; (2) It cannot be removed from certain inorganic substances contained in the filled flux unless it is heated above 500°C Crystal water; (3) Certain metal powders contained in the filler flux contain hydrogen that cannot be removed unless heated above 300°C; (4) When heated to high temperatures, the oxygen that enters through the skin gaps accelerates the oxidation to make the filler flux Quality deterioration; and (5) Wetting through skin crevices makes it impossible to manufacture low-hydrogen flux-cored wires.

Thus, seamless flux-cored wires have been developed in order to be able to manufacture low-hydrogen flux-cored wires. This type of low hydrogen flux cored wire is manufactured by filling a steel pipe with flux. The filled steel pipe is heated to a temperature between 600 and 800°C for dehydrogenation. The water in the filled flux is converted to atomic hydrogen by the chemical reaction given below and diffuses through the skin.

In the formula, Me: reducing agent or other metal components in the flux and the inner wall of the epidermis

H ₂ O = water in filled flux

To reduce water and other sources of hydrogen (potential hydrogen), the wire must be heated to a higher temperature. On the other hand, in order to obtain good wire feeding performance, the conditions of skin softening annealing must be properly controlled. However, the conventional process with one heat does not provide a welding wire with a satisfactorily dehydrogenated flux and a satisfactorily softened skin. Doing a strong dehydrogenation treatment causes excessive softening of the skin which, depending on the wire gauge, can impair wire feed during welding. Soft annealing of wires with adequate skin hardness at lower temperatures will result in insufficient dehydrogenation, increased amounts of diffusible hydrogen, and reduced crack resistance of the weld metal. Conventional heating processes cannot meet the increasing demands for welding wires with lower hydrogen content and for higher wire feed speeds.

In order to solve the above problems, the inventors provide a new process for manufacturing welding wire, which allows a strong dehydrogenation treatment and provides an optimal wire feed speed, by optimizing the heating of the two heating processes of dehydrogenation and skin softening, Instead of conventional one-time heating. Main features of the present invention are as follows:

(1) A process for manufacturing a seamless flux-cored wire for dehydrogenation by high-temperature heating, the process comprising the steps of: directly electrically heating a straight welding wire, which is a metal tube filled with flux, at a temperature between 620 and 1100°C and have a diameter of 8 to 15 mm, by passing the welding wire through the first and second pair of roller electrodes arranged at a distance of 2 to 5 m along the path of the welding wire and passing through the toroidal transformer arranged between the two pairs of roller electrodes to heat the opening; cool the heated wire to below 500°C with a heat transfer coefficient below 250kcal/m ² h°C (≈214.98W/(m ² ·K), the same below); and pull the cooled wire Extend to a diameter between 0.8 and 4mm.

(2) A process for manufacturing a seamless flux-cored wire that uses high-temperature heating for dehydrogenation, the process comprising the steps of: directly electrically heating a straight welding wire, which is a metal tube filled with flux, at a temperature between 620 and 1100°C and have a diameter of 8 to 15 mm, by passing the welding wire through the first and second pair of roller electrodes arranged at a distance of 2 to 5 m along the path of the welding wire and passing through the toroidal transformer arranged between the two pairs of roller electrodes Heating through openings; heat the preheated welding wire to a temperature between 600 and 800°C in a gas heating furnace or an electric heating furnace, and cool the heated welding wire to 500°C with a heat transfer coefficient below 250kcal/m ² h°C below; and drawing the cooled wire to a diameter between 0.8 and 4mm.

(3) A process for manufacturing a seamless flux-cored wire for dehydrogenation by high-temperature heating, the process comprising the steps of: directly electrically heating a straight welding wire, which is a metal tube filled with flux, at a temperature between 620 and 1100°C and have a diameter of 8 to 15 mm, by passing the welding wire through the first and second pair of roller electrodes arranged at a distance of 2 to 5 m along the path of the welding wire and passing through the toroidal transformer arranged between the two pairs of roller electrodes Heating through openings; cooling the heated wire to below 500°C with a heat transfer coefficient below 250kcal/m ² h°C; stretching the cooled wire to a diameter between 2 and 7 mm; in a gas heating furnace or electric Heating the stretched welding wire to a temperature between 600 and 800°C in a heating furnace; cooling the heated welding wire to below 500°C with a heat transfer coefficient below 250kcal/m ² h°C; and drawing the cooled welding wire Extend to a diameter between 0.8 and 4 mm.

The above-mentioned processes according to the present invention can produce flux-cored wires with a diameter of 0.8 to 4 mm by simply drawing a wire with a diameter of 8 to 15 mm after flux dehydrogenation and skin softening treatment. By directly heating the straight seamless flux-cored welding wire with a diameter of 8 to 15 mm in a continuous flow process without sparks and cooling the heated welding wire to below 500 °C with a heat transfer coefficient below 250 kcal/m ² h °C, it can be obtained Seamless flux-cored welding wire containing no more than 5ml of diffusible hydrogen per 100g of deposited metal. Then the dehydrogenated welding wire with a diameter of 8 to 12 mm is drawn into a seamless flux cored wire with a diameter of 2 to 4 mm whose skin hardness is controlled to a Vickers hardness of 180 to 250 Hv. When the diameter of the raw wire is limited to about 8 to 12 mm, a seamless flux cored wire with a diameter of 0.8 to 1.6 mm and a skin hardness controlled at 200 to 250 Hv Vickers hardness can be obtained. In addition, the diameter of the green wire to be heat-treated and the hardness of the processed wire can be selected from a wide range depending on the chemical composition of the steel strip used to manufacture the blank tube.

Ultra-low hydrogen welding wire can be manufactured by dehydrogenating and skin softening heat-treating raw wire with a diameter between 8 and 15 mm and drawing the wire to a diameter between 2 and 7 mm. First, green wire with a diameter between 8 and 15 mm was dehydrogenated with direct electrical heating. The wire, drawn to a diameter of 2 to 7 mm, is then heated in a continuous gas or electric furnace for skin softening and dehydrogenation. The product obtained in this way is an ultra-low hydrogen flux-cored welding wire which contains no more than 3ml of diffusible hydrogen per 100g of deposited metal and whose skin hardness is controlled at 150 to 250Hv Vickers hardness.

Processes according to the present invention eliminate the need for pre-baking filler flux. Even if the flux contains a lot of water, no pre-baking or other strong drying treatment is required. By dehydrogenation of raw tubes with a diameter of 8 to 15 mm and additional dehydrogenation of tubes stretched to a diameter of 2 to 7 mm, without any such pre-baking strong drying treatment, the concentration per 100 g of deposited metal can be obtained. Ultra-low hydrogen flux-cored welding wire with diffusible hydrogen not exceeding 3ml.

The processes of the present invention also eliminate the trouble conventionally encountered in conditioning flux materials containing crystallization water or hydrogen. The dehydrogenation of wires with diameters between 8 and 15 mm at temperatures up to 1100 °C combined with the subsequent dehydrogenation of wires drawn to diameters of 2 to 7 mm makes it unnecessary to adjust the crystallization contained in the filler flux Water or hydrogen can produce ultra-low hydrogen flux-cored wire with no more than 3ml of diffusible hydrogen per 100g of deposited metal.

In addition, performing dehydrogenation heating and skin softening heating in separate processes enables selection of optimal conditions for each heating. Optimum heating measures for dehydrogenation and skin softening in the separation process ensure enhanced dehydrogenation and stable wire feeding even under severe bending of the hose during welding.

Figure 1 shows the principle of direct electrical heating of welding wire passing through a toroidal transformer according to the invention.

Fig. 2 graphically shows the relationship between the skin hardness control zone and the skin hardness of welding wires having a diameter of 8 to 15 mm after softening annealing.

Fig. 3 graphically shows the relationship between the skin hardness control region and the skin hardness of a welding wire heated and drawn to a diameter of 2 to 7 mm after softening annealing.

Figure 4 graphically represents the relationship between heating time and temperature in a combination of direct electrical heating and heating in a tunnel furnace.

Fig. 5 graphically shows the relationship between heating time and temperature when heating in a continuous tunnel furnace.

Figure 6 graphically shows the relationship between the amount of diffusible hydrogen and the horizontal position and incidence of hydrogen-induced cracking in fillet welds.

Fig. 7 graphically shows the relationship between the amount of diffusible hydrogen, the number of shrinkage cavities formed, and the occurrence rate of air gaps.

FIG. 8 graphically shows the relationship among the heating time, the skin temperature of the flux-cored wire, and the flux temperature in Example 1. FIG.

FIG. 9 graphically shows the relationship among the heating time, the skin temperature of the flux-cored wire, and the flux temperature in Example 2. FIG.

FIG. 10 graphically shows the relationship among the heating time, the skin temperature of the flux-cored wire, and the flux temperature in Example 3. FIG.

11 is another graph showing the relationship among the heating time, the skin temperature of the flux-cored wire, and the flux temperature in Example 3. FIG.

Fig. 12 graphically shows the relationship between the heating time and the amount of diffusible hydrogen in each example.

The following paragraphs describe the details of the invention with reference to the drawings.

Figure 1 shows the principle of direct electrical heating of welding wire passing through a toroidal transformer according to the invention. As shown in FIG. 1, a pair of roller electrode units 2 and 3 are arranged with a given distance therebetween, and a welding wire 1 is sandwiched between opposing roller electrodes 2a and 2b and 3a and 3b constituting the roller units 2 and 3. between. The moving wire 1 travels forward while keeping in contact with the peripheral surfaces of the pair of roller electrodes 2a and 2b and 3a and 3b.

A toroidal transformer 4 is centrally arranged between the pair of roller electrode assemblies 2 and 3 so that the welding wire passes through the opening in the transformer. The transformer comprises, for example, a core consisting of hollow square sheets of electrical steel having the desired properties to form a magnetic circuit, laminated to the desired thickness, forming a square leak-off opening in the centre. The transformer 4 has a primary coil 5 of long wire wound on each of four sides arranged 90° apart from the adjacent side. Both ends of the primary coil 5 are connected to a power supply E. As shown in FIG. The roller electrodes 2 and 3 are electrically connected to each other by means of a conductive member 6 . The connection end of the conductive member 6 is slidably kept in contact with the roller electrode through the slider 7 .

Since the cross-sectional area and material of the conductive member 6 can be selected as desired, it is easy to maintain the ratio of the resistance _R1 of the heated welding wire to the resistance _R2 of the conductive member as _R1 >> _R2 . Current passing through the circuit heats the wire to temperatures as high as 1100°C quickly and efficiently. At very low spark rates, power efficiency is as high as 90 to 95%, compared to about 50% in high-frequency induction heating. Since the secondary impedance can be kept lower than the primary impedance, voltage fluctuations are minimal. Since the supply voltage is consumed for heating the welding wire between the first and second roller electrodes, the first and second roller electrode arrangements have substantially equal potentials. Since the first and second roller electrode arrangements can thus be grounded, no current can leak from between the first and second roller electrode arrangements. In addition, the arrangement of the roller electrode units at intervals of not more than 2 to 5 m contributes to making the heating unit compact.

Rapid direct electrical heating via toroidal transformers for optimal dehydrogenation and skin softening simultaneously or separately. In a separate process, dehydrogenation heating to between 620 and 1100° C. is performed in a preceding stage in order to reduce the amount of diffusible hydrogen. Skin softening Heating to between 600 and 800°C is performed in a later stage to control the hardness of the skin (increase wire feed speed and prevent wire breakage). If the dehydrogenation in the preceding stage is performed on a slower moving larger diameter wire, the subsequent drawing and surface treatment will be sufficient to obtain the desired product. Therefore, it is best to dehydrogenate larger diameter wires between 8 and 15mm in diameter.

If larger diameter wires between 8 and 15 mm moving slower than the thinner ones are dehydrogenated in a previous stage, no further process than subsequent drawing is required to obtain 5ml of welding wire. It is ineffective to make ultra-low hydrogen wires with bonded fluxes that contain more water than non-bonded fluxes because the excess water must be removed by prebaking or other intensive drying treatments. Conversely, dehydrogenation of larger diameter wires between 8 and 15 mm in diameter with subsequent heating of reduced diameter wires from 2 to 7 mm in diameter mainly aimed at softening the skin but also achieving some additional The combination of dehydrogenation treatment makes it possible to manufacture ultra-low hydrogen welding wire containing no more than 3ml of diffusible hydrogen with only slightly dry bonding flux.

Figure 2 shows the relationship between the skin hardness of welding wires with a diameter of 8 to 15 mm and the skin hardness control zone after softening annealing, while Figure 3 shows the skin hardness after heating and the skin hardness after softening heating of welding wires drawn to a diameter of 2 to 7 mm Relationships between control areas. As shown in Fig. 2 and Fig. 3, the stable wire feeding zone is different between the welding wire with a diameter of 8 to 15 mm and the welding wire with a diameter of 2 to 7 mm. The wire feeding mechanism and the welding point are separated by a few meters or tens of meters and connected by a hose. When the hose has to be bent to meet job site conditions, such as when welding bends in a confined space, the high resistance created between the inner wall of the hose and the passing welding wire will impair the stability of the wire feeding.

Since the resistance value varies with the bending condition of the hose and the wire diameter, it is necessary to prepare a welding wire with an appropriate skin hardness to meet the job site conditions. As the filling ratio increases, the skin hardness decreases, as shown in Figure 3. Welding wire with a skin hardness exceeding 250 Hv tends to break and make it difficult to pass the tip around the spool. This is the breaking limit. On the other hand, welding wire with a skin hardness of less than 150 Hv tends to warp between the wire feed roller and the hose or at the inlet end of the power tip and impair the smoothness of wire feeding. This is the warp limit. Therefore, a stable wire feeding zone can be obtained when the hardness of the skin is kept between the breaking limit of 250Hv and the warping limit of 150Hv.

Figure 4 shows the relationship between heating time and temperature in a process in which direct electric heating is combined with heating in a tunnel-type arc furnace. It can be seen that direct electric heating rapidly increases the skin temperature to 800°C. Then, the temperature of the part of the flux that is in contact with the inner surface of the skin rises to 400°C and continues to rise along the flux temperature curve A. As heat is transferred through the flux, the temperature of the core portion of the flux rises along the flux temperature curve B with some time lag, reaching substantially the same value as the skin temperature in about 5 minutes. Fig. 5 shows the relationship between heating time and temperature in a heating process using a continuous tunnel furnace. Unlike the situation shown in Fig. 4, the skin temperature gradually increased to 800°C within 2 to 3 minutes. The flux temperature was also ramped up to 800°C in about 8 minutes. It can be seen from the above that direct electric heating can quickly heat to high temperature, and can carry out continuous flowing water heating by directly connecting several processes, and can heat welding wire with larger diameter or thinner skin with high thermal efficiency.

Figure 6 shows the relationship between the amount of diffusible hydrogen and hydrogen-induced cracking in horizontal and fillet welds. In other words, this graph shows the relationship between the amount of diffusible hydrogen contained in 100 g of deposited metal and the tensile strength of weld metal. When the content of diffusible hydrogen is 5ml, the tensile strength of the weld metal drops sharply to 60kgf/mm ² (=60×9.8×10 ⁶ Pa). When the content exceeds 7 ml, the tensile strength drops to 50 kgf/mm ² (=50×9.8×10 ⁶ Pa) and the possibility of hydrogen-induced fracture increases. Therefore, it is best to keep the diffusible hydrogen content in 100g of deposited metal below 5ml.

Figure 7 shows the relationship between the amount of diffusible hydrogen, the number of shrinkage cavities formed, and the incidence of air voids (ie, the protective quality of the primer). In Fig. 7, the deposited metal is the metal obtained by horizontal fillet welding of a steel plate covered with a 20 μm thick inorganic zinc primer, the amount of diffusible hydrogen is the content in 100 g of the deposited metal, and the number of shrinkage cavities and gas The gap occurrence rate is a value in a 50 cm long weld. As shown in Fig. 7, the number of shrinkage cavities and the occurrence rate of air voids tend to sharply increase when the diffusible hydrogen content exceeds 10ml. In order to maintain good primer protection qualities, it is necessary to keep the diffusible hydrogen content below 10ml. Considering the resistance to hydrogen-induced cracking shown in Figure 6 and the protective quality of the primer shown in Figure 7, it is necessary to keep the diffusible hydrogen content at least below 7ml, preferably below 5ml. The optimal flux filling ratio of the seamless flux cored wire according to the present invention is 10 to 26%.

example

Example 1

A 21mm diameter unprocessed welding wire for JIS Z#3313 YEW-C50DR standard seamless flux-cored welding wire, the inner cavity is filled with flux to 15% (by weight), subjected to tension to reduce to 10mm, so that the inner cavity is filled with flux Filled to more than 100% (according to bulk density) in order to carry out dehydrogenation treatment, by making the welding wire pass through the first and second roller electrode devices arranged at a distance of 5m at a speed of 20m/min (≈0.333m/s) The toroidal transformer is used to directly heat the welding wire with a diameter of 10mm to 1080°C at a speed of 72°C/S. Fig. 8 shows the relationship between skin temperature and flux temperature. More specifically, FIG. 8 shows the relationship between the heating time and the cored wire skin temperature and flux temperature. After electric heating, the temperature of the skin rises rapidly to 1080°C immediately, and the temperature of the part of the flux that is in contact with the inner surface of the skin rises rapidly to 300°C and continues to rise along the flux temperature curve A. As heat is transferred through the flux, the temperature of the core portion of the flux rises along the flux temperature curve B with some time lag, reaching about 950° C. within 1 minute, as shown in FIG. 8 . The heated welding wire is air-cooled for 4 minutes with a heat transfer coefficient of 50kcal/m ² h (≈42.996W/(m ² ·K), the same below)°C, and then cooled rapidly and controlled at 2.4°C/S below 500°C Rate water cooling. The wire was then subjected to drawing and surface treatment processes to obtain a finished wire with a diameter of 2.4 mm. The 2.4mm diameter welding wire thus obtained is used at 42V, a welding speed of 35cm/min (≈0.058m/s, the same below), a welding wire extension of 30mm, and 30L/min (≈0.5×10 ^-3 m ³ /s, The same below) use 550V welding under the amount of carbon dioxide outgassing. The obtained diffusible hydrogen content per 100 g of the deposited metal measured by the gas chromatography method was 4.2 ml.

Example 2

A raw welding wire for JIS Z3313 YEW-C50DR standard seamless flux-cored wire lumen filled with flux to 18% (by weight) 21.5mm in diameter, subjected to stretching and surface treatment processes to lighten to 10.5mm, so that the inner The cavity is filled to more than 100% (by bulk density) with flux. For the dehydrogenation treatment, the 10.5 mm diameter wire is passed at a rate of 53 ° C / S by passing the welding wire at a speed of 20 m / min through the toroidal transformer arranged between the first and second roll electrode devices at a distance of 5 m. The welding wire is directly heated to 800°C. Fig. 9 shows the relationship between skin temperature and flux temperature. More specifically, FIG. 9 shows the relationship between the heating time and the cored wire skin temperature and flux temperature. After electric heating, the temperature of the skin immediately rises rapidly to 800°C, and the temperature of the part of the flux that is in contact with the inner surface of the skin rises rapidly to 200°C and continues to rise along the flux temperature curve A. As heat is transferred through the flux, the temperature of the central portion of the flux rises along the flux temperature curve B with some time lag, reaching about 800° C. within 1 minute, as shown in FIG. 9 . The heated welding wire is reheated at 800°C for 2 minutes in a directly connected gas or continuous heating furnace, cooled in air with a heat transfer coefficient of 50kcal/m ² h°C for 2 minutes, and then passed through a temperature of 2.5°C/S below 500°C Rapid and controlled cooling of the rate comes with water cooling. The wire was then subjected to drawing and surface treatment processes to obtain a finished wire with a diameter of 2.0 mm. The 2.0mm diameter welding wire obtained in this way is used to use 500A welding wire at 38V, 35cm/min welding speed, 25mm welding wire extension and 25L/min (=4.167×10 ^-4 m ³ /s, the same below) carbon dioxide outgassing. of welding. The resultant diffusible hydrogen content measured by gas chromatography was 4.5 ml per 100 g of the deposited metal.

Example 3

A 21 mm diameter unprocessed welding wire for JIS Z#3313 YEW-C50DR standard seamless flux cored wire V, filled with flux to 12% (by weight) in the inner cavity, subjected to tension to reduce to 10mm, so that the inner cavity is Flux filled to more than 100% (by bulk density). In order to carry out the dehydrogenation treatment, by making the welding wire pass through the toroidal transformer arranged between the first and second roll electrode devices at a distance of 2.5 m at a speed of 60 m/min (=1 m/s, the same below), the wire is heated at 350 The 10mm diameter welding wire was directly electrically heated to 880°C at a rate of °C/S. Fig. 10 shows the relationship between skin temperature and flux temperature. More specifically, FIG. 10 shows the relationship between the heating time and the cored wire skin temperature and flux temperature. After electric heating, the temperature of the skin rises rapidly to 880°C immediately and the temperature of the part of the flux that is in contact with the inner surface of the skin rises rapidly to 200°C and continues to rise along the flux temperature curve A. As heat is transferred through the flux, the temperature of the central portion of the flux rises along the flux temperature curve B with some time lag, reaching about 800°C within 1 minute, as shown in FIG. 10 . The heated welding wire is air-cooled for 4 minutes with a heat transfer coefficient of 20kcal/m ² h°C (≈17.16W/(m ² ·K), the same below), and then rapidly heated at a rate of 1.6°C/S below 500°C. Control cooling water cooling. The wire was then drawn to a diameter of 3.2 mm, which was heated to 800° C. for 5 minutes in a tunnel furnace to soften the skin and dehydrogenate it. Fig. 11 shows the obtained relationship between the skin temperature and the flux temperature. More specifically, Fig. 11 shows the relationship between the heating time and the cored wire skin temperature and flux temperature. As shown in Figure 11, the skin temperature rose to 800°C within 3 minutes. The flux temperature also rose to about 800°C within 6 minutes. The heated welding wire is air-cooled again for 3 minutes with a heat transfer coefficient of 80kcal/m ² h°C (≈68.64W/(m ² ·K), the same below), and then rapidly heated at a rate of 2.2°C/S below 400°C. Control cooling water cooling. The wire was then subjected to drawing and surface treatment to obtain a finished wire with a diameter of 1.2 mm. The 1.2mm diameter welding wire thus obtained was used for welding at 270A at 30V, welding speed of 35cm/min, wire extension of 20mm and carbon dioxide outgassing of 25L/min. The obtained diffusible hydrogen content per 100 g of the deposited metal measured by gas chromatography was 2.1 ml.

Fig. 12 shows the relationship between the heating time and the amount of diffusible hydrogen in each example. The amount of diffusible hydrogen in 100g of deposited metal is 4.2ml in Example 1, 4.5ml in Example 2, and in Example 3 in the welding wire which is directly electrically heated to 880°C and water-cooled at 500°C after air cooling is 5.0ml, and 2.1ml in the welding wire that continues to be heated and cooled in the tunnel arc furnace. It is evident that all welding wires prepared by the process of the present invention contained much lower diffusible hydrogen than the conventional welding wire prepared for comparison without heating. Therefore, the processes according to the present invention can efficiently produce low-hydrogen flux-cored welding wire by reducing the content of diffusible hydrogen, which has excellent crack resistance and primer protection quality, and is suitable for welding high-strength steel and structural steel.

Claims (3)

1. A process for producing seamless flux-cored welding wire by dehydrogenating a welding wire prepared by filling a metal with flux by heating at a high temperature, the process comprising the steps of: A straight welding wire with a diameter of 8 to 15 mm is directly electrically heated to 620 by passing the welding wire through the first and second pair of roller electrodes arranged at a distance of 2 to 5 m along the path of the welding wire and passing through the toroidal transformer arranged between them. For temperatures between 1100°C and 1100°C, the straight wire includes a metal tube filled with flux; Cool the heated welding wire to a temperature not higher than 500°C with a heat transfer coefficient not higher than 250kcal/m ² h°C (≈214.98W/(m ² ·K), the same below); and The cooled wire is drawn to a diameter between 0.8 and 4 mm. 2. A process for producing seamless flux-cored welding wire, which is produced by dehydrogenating a welding wire prepared by filling a metal tube with flux by heating at a high temperature, the process comprising the steps of: A straight welding wire with a diameter of 8 to 15 mm is directly electrically heated to 620 by passing the welding wire through the first and second pair of roller electrodes arranged at a distance of 2 to 5 m along the path of the welding wire and passing through the toroidal transformer arranged between them. For temperatures between 1100°C and 1100°C, the straight wire includes a metal tube filled with flux; heating the wire at a temperature between 600 and 800°C in a gas or electric furnace; Cool the heated wire to a temperature not higher than 500°C with a heat transfer coefficient not higher than 250kcal/m ² h°C; and The cooled wire is drawn to a diameter between 0.8 and 4 mm. 3. A process for manufacturing seamless flux-cored wire by dehydrogenating a wire prepared by filling a metal tube with flux by heating at a high temperature, the process comprising the steps of: A straight welding wire with a diameter of 8 to 15 mm is directly electrically heated to 620 by passing the welding wire through the first and second pair of roller electrodes arranged at a distance of 2 to 5 m along the path of the welding wire and passing through the toroidal transformer arranged between them. For temperatures between 1100°C and 1100°C, the straight wire includes a metal tube filled with flux; Cool the heated welding wire to a temperature not higher than 500°C with a heat transfer coefficient not higher than 250kcal/m ² h°C; Draw the cooled wire to a diameter between 2 and 7mm; heating the drawn wire to a temperature between 600 and 800°C; Cool the heated wire to a temperature not higher than 500°C with a heat transfer coefficient not higher than 250kcal/m ² h°C; and The cooled wire is drawn to a diameter between 0.8 and 4mm.

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