JPS6092078A - One side arc welding - Google Patents

Abstract

PURPOSE:To prevent occurrence of low temperature cracks in a weld zone and obtain good penetration bead form by constituting back flux making baked type flux having specified bulk density a lower layer and making molten type flux having specified flux form and size distribution an upper layer and laminating the upper and lower layers to specified thickness. CONSTITUTION:The back flux used in one side arc welding is constituted by scrattering two kinds of flux in two layers. Baked type flux having bulk density adjusted to 0.80-1.40g/m<3> is used for the lower layer of the back flux and scattered to the thickness of 1-5mm.. Molten type flux or mixed material type flux or mixture of them for which addition of viscosity binder is restricted to less than 3.0%, and grain size distribution is so adjusted that grains having diameter of below 500mu is more than 80%, and grains of below 150mu is less than 15% is used for the upper layer of the back flux and scattered to the thickness of 2-5mm..

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an improvement in a single-sided arc welding method for high-strength steel. Prevents cold cracking in welded parts,
The present invention also relates to a single-sided arc welding method that can produce an excellent shape.

The single-sided arc welding method is a method in which a backing material is pressed against the back surface of the groove of the material to be welded, and arc welding is performed from the front side to form a bead on the front and back of the material to be welded. It is widely used for welding steel as an extremely efficient welding method because there is no need to reverse the process and the joint can be completed with a small number of welds. In particular, the method of using a combination of true metal and prefectural flux gold as a backing material has excellent back bead stability and high current resistance, and is the most widely used method for single-sided arc welding of flat plates.

That is, as shown in Fig. 1, in this method, a backing flux 4, which has been sprinkled to a uniform thickness on a backing metal 3, is applied to the backside of the welded materials 1 and 1' by an air hose along the weld line. In this method, arc welding is performed using a welding wire 6 from the pressing front side using a push-up mechanism such as No. 5 to generate weld metal 2 and complete the joint.

By the way, recently, high-strength steel of 60 kg/mm2 or more has been frequently used in Yuzu structures to reduce weight and cost. A contact method is required. The present invention focuses on this point and attempts to provide an excellent single-sided arc welding method for high-strength steel.

[Prior art]

By the way, the purpose of the back flux in single-sided arc welding is to act as a packing material together with the brazing material to form an excellent member bead.

Therefore, various improvements have been made to the backing flux in order to obtain better performance. That is, the most effective means is generally to coat the surface of the flux particles with a caking binder that melts with welding heat and exhibits caking properties.

As the caking binder, carbohydrates such as dextrose and butyl sugar, or resins such as phenol resins are used. If about 4 to 6% of these back flux particles are coated on the surface, they will melt due to welding heat and bind the flux particles together, so the back flux will solidify during welding, thereby improving fire resistance. It is fixed on the backing fund.

This enhancement of the Z-locking effect of the backing flux prevents molten metal from burning through and has a remarkable effect on forming a healthy backing bead.

For example, Japanese Patent Publication No. 48-22572 states that at least the part between the copper pad and the material to be welded that is in contact with the back surface of the groove of the material to be welded contains 40% or more of particles finer than 840μ, and
A single-sided arc welding method in which granular flux, which is 70% or more coarser than μ and contains a resin that melts and hardens with welding heat, is placed. Japanese Patent Publication No. 49-18704 discloses a fire-resistant material containing 2 to 6% of thermosetting resin on the backing metal, and a backing material containing 0.5 to 2.0% of thermosetting resin on the backing metal. Single-sided bath welding method in which two layers of this solvent are bath-welded. JP-A No. 54-57438 discloses that 80% or more of particles larger than 74μ are present on a metal plate. Moreover, the particles that are coarser than 149μ are 30
- Powdered refractory solvent fc that accounts for more than 2 to 10 m thickness is sprayed, and on the top, particles finer than 840μ account for 50 or more, and particles coarser than 74μ account for 40 or more,
A single-sided welding method in which a powder backing flux containing a thermosetting binder is further sprinkled to a thickness of 2 to 6 times.

Other single-sided welding methods have been proposed.

However, both carbohydrates and fats used as caking binders are organic substances, and at the time of injection,
A part of it decomposes into co, co2 or H2 gas, and in particular, the H2 component decomposes in the bath weld metal as a mark), causing a total increase in diffusible hydrogen in the weld metal.

On the other hand, in general, the most important point in bath welding of high-strength steel is the problem of cold cracking in the bath welding part caused by diffusible hydrogen. In other words, when excessive diffusible hydrogen exists in the bath contact area, hydrogen accumulates in inclusions, grain boundaries, or microbial P parts in the metal, creating extremely large internal stress, which in turn causes tensile stress due to thermal contraction, etc. When the tensile strength is increased, cracking occurs at low temperatures of about 100° C. or lower, and this problem becomes more severe as the tensile strength increases.

Such low-temperature cracking occurs similarly in single-sided arc bath welding, but single-sided arc welding in particular has a larger heat input seam than normal multilayer welding, and the crystal grains of the weld metal tend to become coarser.

Therefore, it is characterized by a large tendency for cold cracking at grain boundaries, and sufficient preventive measures are required.

By the way, as mentioned above, the flat iron used for single-sided arc welding,
The caking pine paste in the weld metal significantly increases the water penetration rate in the weld metal, and it is a 115%
This is undesirable from one point of view, and the current situation is that such single-sided arc welding is not used for high-strength steel of 60 kg 7 m2 class or higher.

[Purpose of the invention]

An object of the present invention is to reduce the amount of flux used in single-sided arc welding of high-strength steel as described above.

To provide an excellent single-sided arc welding method for high-strength steel that prevents cold cracking caused by diffusible hydrogen without deteriorating king performance. The inventors of the present invention have carried out various efforts to achieve all of the above objectives, and have found that in order to prevent cold cracking caused by hydrogen in single-sided arc welding as described above, it is necessary to add a caking binder to the back flux. It is necessary to limit the total amount of the fan to as little as possible, and to obtain an excellent back bead shape, two types of medicinal flux f! : It was found that the skewer used to spray in two layers and determine the particle size distribution and flux form was extremely heavy.

[Structure and operation of the invention]

The present invention has been made based on the above study results, and the gist thereof is to apply a single-sided flux to the backing metal and press the flux to the back side of the groove of the material to be bathed. In the arc welding method, two types of flux are spread in two layers, and the lower I@end rough flux is used to adjust the high density to 0.80 to 1.40 g/1tn5. flux? 1 to 5 J'J's, and on top of that, as an upper layer spring flux, the amount of caking binder is added, and the total amount of flux is limited to 3° or less, and the particle size structure is A molten flux or raw material mixed flux, or a mixture of these fluxes, with a diameter of 500μ or less is adjusted to 80 or more, and a particle size of 105μ or less is 15% or less. 4+ (11- Features of one-sided arc common welding method)

In the present invention, the reason why two types of Todoro flux are sprayed on the backing metal is that the backing fluxes with different characteristics are spread in two layers, upper and lower, to completely prevent cold cracking caused by hydrogen.
Moreover, he discovered that Kogane was an extremely effective means of obtaining a sunken bead shape.

In other words, the upper layer contains a backing flux with a specified grain size and black form so that excellent solidification can be obtained even with a small amount of caking binder, and the lower layer contains a high-density flux to stabilize the excess build-up of the reinforcement. A backside flux with a specified density and flux type is sprayed.

The reason why all the caking binder is added to the back flux of the upper layer is that, as mentioned above, the caking binder melts during welding and solidifies the back flux, thereby significantly improving the backing performance. The effect of such a caking binder is that only the top and center fluxes are sufficient, and this makes it possible to obtain excellent backing performance.

On the other hand, in order to prevent cold cracking caused by hydrogen, it is necessary to completely limit the amount of caking binder added, and according to the results of the study, the amount of caking binder added to the upper layer p flux is It is necessary to limit free time to 3.0 inches or less. .

The caking binder of this binding table is a substance that, when added to the central flux, melts during welding due to the heat contact of the table 4 and has the effect of caking the flux particles together.Specifically, dextrin, These include carbohydrates such as starch and glucose, or threatening resins such as phenol resin, acrylic resin, and vinyl acetate resin.

If more than 3.0 parts of these organic substances are added to the mixture, there is a risk that cracks due to hydrogen may occur in the weld metal or base metal due to heat effects.

By the way, limiting the cooling mass of the caking binder to 3.0% or less does not deteriorate the solidification ability of the backing flux, and countermeasures are required to prevent this.

Therefore, in the present invention, first, the particle size structure and form of the upper back flux are fully specified.

In other words, in order for a small amount of caking binder to work effectively, (a) the size of the individual voids formed between the back flux particles must be small and the unevenness formed on the particle surface must be small; . and (b) the flux density is moderately large and the flux stripes are good. Both are valid.

In order to reduce the size of the voids between particles, it is effective to make the particle size composition of the back flux finer. More than 80% of the particles have a particle size of 500μ or less, and those with a particle size of 105μ or less. must be 15 inches or less. That is, if the particle size is less than 500 μm, if it is less than 80%, the pore size is large and sufficient solidification of the flux is obtained.

However, if 105μ or less exceeds 15%'z, the grains become excessively fine and the center blacks become tightly packed, which actually deteriorates the assimilation properties, and the air permeability decreases, causing caking and welding heat. This is not preferable because the gas generated by the escaping phase #<m causes gas bubble defects in the welding river.

Next, in order to reduce the unevenness formed on the surface of the flux-free particles and to increase the high density excessively, the flux type fxM k of the upper back flux, the I"ta molten type flux, and the raw material mixed type flux are used. or a mixture thereof.

The molten flux is a flux manufactured by melting it in a Ryoshina quasi-air furnace or the like whose composition is adjusted to an appropriate composition according to the purpose, cooling and solidifying it, and then crushing and grinding it into pellets. Further, the raw material mixed type flux is a flux obtained by mechanically mixing raw materials of appropriate particle size according to the intended composition.

Conventionally, sintered flux, which is granulated and fired with a solidifying agent such as raw powder all-water glass, has been mainly used as the backing flux, but sintered flux has irregularities and voids on the surface of individual particles. Therefore, when a caking binder is added to this, the caking binder tends to segregate in recesses or voids, making it difficult to obtain an effective caking effect.

On the other hand, bath melt type or raw material mixed type flux is originally a rich lump that has been pulverized and sized, and the particle surface has few voids and irregularities, so caking pinpoint is effective. It becomes possible to improve the solidification ability by being coated.

Furthermore, since molten and raw material mixed fluxes are not granulated, there are fewer voids inside and on the surface of the particles, and their high density is thicker than that of sintered fluxes, so the flux compacts better during backing, so it has excellent solidification ability. It is also a big advantage that it can be obtained.

The above-mentioned molten type or raw material mixed type flux can be used to form grooves on the upper back side flask to prevent leakage and overcasting.
It becomes possible to use a skewer to obtain a familiar Urabi r, but on the other hand,
The drawback is that the excess DgJ of the crystal beads becomes unstable.

In other words, the fact that the raw material mixed type flux has a high degree of filtration contributes to the improvement of solidification ability, but on the other hand, when it is converted into bath molten slag during the back bead formation process, , the decrease in volume is small, and there is a tendency that the desired amount of sleep is insufficient to accommodate the bead excess.

As a countermeasure for this point, in the present invention, it is necessary to use two layers of νA flux, and to completely coat the lower layer VC^1 with a small 6° wave forming flux. It is relatively easy to control the high density of the sintered flux, and the high density of the sintered flux in the present invention is required to be 0.80 to 14 sq/rm 3. In other words, when the ura density of the lower layer off flux exceeds 1.50 Zo/Fuchi 3, the tower that stabilizes the flourishing of the back bead in combination with the upper layer back flux is 1.1! I 8elI, and
0.80! If J/♂ is 7 hours old, the excess amount of small bee P will be too large, which is not preferable because there will be problems such as water leakage.

Also, depending on the thickness of the nose flux, it is necessary to set the upper layer back blacks to 2 to 5 meters and the lower layer off flux to 1 to 5 meters.

If the upper layer≠flux distribution level is less than 2, it solidifies during welding, there is insufficient back flux that can control the back bead shape, and the bead shape is not smooth and satisfactory.

On the other hand, if it exceeds 5+m'i, the solidified portion of the flux will be excessive, the effect of the lower M flux will be weakened, and the excess of the flux will become unstable.

If the thickness of the F-layer machine flux is less than 1 layer, the A bead excess will become unstable, and if it exceeds 5 layers, it will become excessive.

By the way, the composition of the upper and lower layer fluxes is TiO2, 5in2. At203. Metal chloride such as MgO, metal such as CaCO31MgCO3, carbonate,
CaF2.

Metal fluorides such as MgF2, deoxidizers such as Sl, At, Mn, and ordinary welding flux components such as iron powder may be used as appropriate depending on the purpose.

Also, caking/ginder is not particularly necessary for T1-/maroon blacks, and it is usually possible to perform it without adding 11> to (-1,μ). However, Ib Lifting platform for bath wetting method with high density of seedlings, or 15
In cases where thin plates with a spacing of less than IW are in bath contact, the front flux on the backing metal may move easily and the backing may become unstable, so it is recommended to add caking agent to the lower layer flux as well. is preferable. It is essential to limit the amount of caking and addition of 9-ingredients to 3.0% or less.

The grain size of the couscous is exactly +1. )+
11 to 1, 40 g/mouth is not particularly specified, but normally it is appropriate that particles with a particle size of 840μ or more are 60 inches or less, and particles with a particle size of 250μ or less are about 20% or less. .

The welding method in the present invention is not particularly limited as long as it is an arc bath welding method, and submerged arc welding method,
Gas seal P arc bath welding method or manual welding method can be applied.

Also, the backing metal is gold W4 to hold the good bead metal along with the backing flux, and it is preferable to use something with good thermal conductivity, such as brass, brass, or aluminum. It is used.

〔Example〕

Examples of the present invention will be described below.

First, the upper and lower fluxes of 8 volatiles UF-1 to UF-8 as shown in Table 1 and the upper layer fluxes of 6 rods LF-1 to LF-6 as shown in Table 2. was created.

In Table 181, UF-1 to UF-4 are upper layer fluxes used in the method of the present invention, and UF-5 to UF-8 are upper layer fluxes used in comparative examples to clarify the effects of the present invention. That is, UF-5 is a caking binder of phenol (fAli is 3.3, and UF-6 is a particle size of 500.
The flux below 105 microns is 75 microns, the UF-7 has a flux of 20.0 microns below 105 microns, and the flux form of UF-8 is sintered flux, which is 3.5 microns, all of which are outside the scope of the present invention.

In Table 2, LF-1 to LF-4 are the lower fluxes used in the method of the present invention, LI='-5., and LF-6 are the lower fluxes used in the comparative example e. That is, L
Ii"-5Vi high scrapness is 1.51) 9/α and the flux form is bath melting flux, LF-6+: 3
+'(If the question is 0 or 7597 cm3, both are outside the scope of the present invention.

In addition, the addition of a caking binder to a good flux is
Each of the caking binders was dissolved in a solvent in advance to form a liquid, mixed with a flux having the desired composition, and then dried at a low temperature of 80 to 120C.

Next, Table 7 Lanox in Zabmano Arc Welding 12, which was used for this actual case (■), is shown in Table 3, and Zabmano Arc Welding and Sunold Arc ("Hand 1 Current Wire x: 141J
Also, on table 4 of all elementary schools, there is a buko (30+70J) used as a test voice board.
R and 80 kg of composition gold No. 5 clothing] J squirrel.

Further, as the bath welding method in this example, the Zabmersoarc MfiA method and the CO2 gas/-rudo arc bath welding method were used. The welding conditions for this joint are shown in table frJli.

The combination of the bath abrasive materials, steel plates, and tB contact conditions shown in each table above is shown in the left column of Table 7. &1 to 5 are examples of the present invention, and 6 to 13 are comparative examples other than the present invention.

On the other hand, for A5, CO2 gas shielded arc bath welding was carried out, but for other welding, submerged arc welding was carried out.

: After finishing, crack inspection and central bead appearance inspection were conducted on the welded part.

As for the crack inspection, we first conducted an internal defect inspection using the UST probe method, and then we actually confirmed the presence or absence of cracks using a macro cross-sectional inspection.1 These results are shown in the right column of Table 7.

This is an example of the present invention.・For K1 to K5, single-sided welds with proper bead shapes without cracks were obtained;
In Nos. 6 to 611, problems occurred due to excessive amount of caking binder in the back flux, irregularities in particle size structure, and irregularities in the shape of the flux, resulting in cracks or poor bead shape. In addition, A12 had a poor center bead shape due to both an excessively large spreading thickness of the upper layer back flux and an excessively small spreading thickness of the lower layer flux.

〔Effect of the invention〕

The embodiments of the present invention have been described above, and it is clear that the present invention prevents hydrogen cracking due to the influence of surface flux in single-sided submerged arc 04 contact of high-strength steel, and maintains a healthy (valley rear part). In addition to making it possible to obtain a backing metal, it is also possible to obtain a sufficiently good back bead shape.

Therefore, it is unlikely that welding of high-tensile steel will become more efficient and more efficient than this. However, the present invention is not limited to the above embodiments.
It can be used commercially for single-sided arc welding of high-strength steel to prevent low-temperature cracking that occurs in the welding joint due to the hydrogen from the caking binder from the k-flux.

[Brief explanation of the drawing]

Figure 41 shows a single-sided arc m weld, a light beam, and an i figure.
Fig. 2 (a>, (b) t is an old view showing the groove shape used in the embodiment of the present invention. 1, 1'... Fractured weld material, 2... tg i & gold metal 3...Shibu Tokin, 4...Acupuncture flux, 5...Air hose, 6...Y binding wire. ---

Claims (1)

[Claims] In the single-sided arc welding method, in which backing flux is sprinkled on the core metal and the backing flux is pressed against the groove layer surface of the material to be welded, two types of backing flux, flux f: are sprinkled in two layers. A method in which high-density t-
0,80~1.40 itc! Spray the sintered flux adjusted to n to a thickness of 1 to 5 Ifl+, and then add caking pine as the upper layer back flux! - limit the amount of addition to 3.0 inches or less, and change the particle size composition to 500μ
The following items are 80 cm or more, and the particle size is 105 μ or less: 1
Melted flux or raw material mixed flux adjusted to 51 or less, or flux t-2 ~
One-sided arc m welding method, which is applied by spraying to a thickness of 5 cm.