JP2001129684A - Pulsed CO2 welding steel wire - Google Patents

Abstract

(57) [Problem] To provide a welding steel wire capable of securing an excellent bee shape, not to mention stabilizing an arc and reducing the amount of spatter in CO ₂ welding. SOLUTION: As a wire for pulse CO ₂ welding, which gives 7 or more pulses per droplet transfer, the composition is as follows: C: 0.15 mass% or less, Si: 0.3 to 2.0 mass%, Mn: 0.5 to 2.5 mass%. , Ti: 0.15 to 0.30 mass%, S: 0.030 mass% or less, Ca: 0.0015 mass% or less, the balance being Fe and unavoidable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel wire for gas shielded arc welding, and more particularly to an advantageous effect of reducing the amount of spatter generated in pulsed CO ₂ welding.

[0002]

2. Description of the Related Art A welding method using a mixed gas of Ar- (5 to 25%) CO ₂ as a shielding gas (hereinafter referred to as a MAG welding method)
Excellent bead shape and less spatter
Widely used in fields requiring high quality welding.
However, when Ar gas is compared with CO ₂ gas, a welding method because the price is expensive and about 5-fold, at the time of ordinary welding, to an inexpensive CO ₂ gas as a main component (40% or more) ( Hereinafter, the method is referred to as a CO ₂ welding method (for example, Japanese Patent Application Laid-Open No. H10-272591).

By the way, in the CO ₂ welding method, there is a problem that spatter is frequently generated due to short-circuiting with a base material (steel plate) and re-arcing, because coarse droplets hang at the tip of the wire and fluctuate by an arc force.

On the other hand, a method of reducing the amount of spatters generated by adding potassium is disclosed in Japanese Patent Application Laid-Open No. Hei 6-218574, but this method cannot provide a satisfactory effect satisfactorily. Was.

Further, Japanese Patent Application Laid-Open Nos. 7-47473 and 7-290241 propose a method of reducing the amount of spatter generated by transferring one droplet to one droplet. This method requires only 1-2 ms for forming one droplet,
In addition, excellent effects can be obtained in MAG welding that enables stable transition. However, for MAG welding
Form droplets 10 to 20 times larger and exhibit unstable behavior
In CO ₂ welding, transfer of one droplet per pulse is difficult. Further, since the base time becomes longer together with the peak time, droplets that could not be transferred by one pulse are short-circuited during the base period, resulting in an increase in spatter generation.

[0006]

As described above, in the pulse CO ₂ welding method, a coarse droplet hangs at the wire tip,
There is a problem that spatters occur frequently due to short-circuit with the base material (steel plate) and re-arcing because of swinging due to the arc force. The present invention has been developed in view of the above situation, and in so-called pulsed CO ₂ welding, it is possible to secure an excellent bee shape, not to mention stabilizing the arc and reducing the amount of spatter. The aim is to propose a wire.

[0007]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies on wire compositions in combination with power supply characteristics, and have obtained the following findings. In other words, in order to stabilize the arc and reduce the amount of spatter, (1) the number of pulses per droplet transfer must be 7 or more, and (2) an appropriate amount of Ti is contained as a wire component, and S and Ca It has been found that limiting the amount to a predetermined range is extremely important. The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows. 1.1 Pulse that gives 7 or more pulses per droplet transfer
A wire for CO ₂ welding, containing: C: 0.15 mass% or less, Si: 0.3 to 2.0 mass%, Mn: 0.5 to 2.5 mass%, Ti: 0.15 to 0.30 mass%, and S: 0.030 mass% or less , Ca: 0.0015 mass% or less, the balance being Fe and unavoidable impurities, a steel wire for pulse CO ₂ welding.

2. A pulse CO ₂ welding wire for applying 7 or more pulses per droplet transfer, wherein mass% is C: 0.15 mass% or less, Si: 0.3 to 2.0 mass%, Mn: 0.5 to 50 mass%. Contains 2.5 mass%, Ti: 0.15 ~ 0.30mass%, K: 0.0001 ~ 0.0030mass% and B: 0.0003 ~ 0.0030mass%, contains one or two kinds, and S: 0.030 mass% or less , Ca: 0.0015 mass% or less, the balance being Fe and unavoidable impurities, a steel wire for pulse CO ₂ welding.

[0010] 3. 1. The steel wire for pulse CO ₂ welding according to 1 or 2, wherein the steel wire has a composition further containing Al: 0.50 mass% or less.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The welding method targeted by the present invention applies an average of 7 or more pulses in accordance with the transition from the formation of one droplet, and oscillates the droplet, and the droplet is formed using a peak current higher than the average current. This is a welding method that allows a smooth transition. Conventionally, low spatter has been achieved by one or two pulses per droplet transfer. However, it takes 10 to 20 times as long as MAG welding to form droplets, and in CO ₂ welding which forms coarse droplets, a short circuit during the base period causes an increase in spatter generation. Therefore, it is necessary to control the base period to be short. For this purpose, it is necessary to lower the peak current or shorten the peak time.
On the other hand, since the pinch force for detaching the droplet increases in proportion to the square of the current, the size of the droplet decreases with the current. Therefore, if the peak current is kept low, the effect of making the droplets fine cannot be obtained.

Therefore, shortening the peak time is effective for shortening the base period, suppressing short circuit, and miniaturizing droplets and suppressing generation of spatter by increasing the pulse. For that purpose, it is necessary to increase the number of pulses applied in accordance with the transition from the formation of one droplet. Here, if the number of pulses per droplet transfer is less than 7, it is not possible to achieve both the prevention of short circuit during the base period and the effect of miniaturizing droplets. Therefore, in the welding method targeted in the present invention, the number of pulses applied per droplet transfer is set to 7 or more. However, the number of pulses per droplet transfer is 30
When the number exceeds the threshold value, it is difficult to apply a stable pulse. Therefore, the upper limit of the number of applied pulses is preferably set to about 30.

The size (weight) of the transferred droplet is
It depends on the average current, peak current, current waveform, protrusion length, wire diameter, and the like. For example, average welding current: 30
In the case of 0 A, peak current: 500 A, base current: 80 A, protrusion length: 20 mm, and wire diameter: 1.2 mm, the average weight of the transferred droplet is 38 mg, and the amount of wire melt per minute is:
The pulse frequency range for this welding method is 384 Hz or more. When the average welding current is 450A, which is the normal use limit, the peak current is 600A,
At a base current of 50 A, a protrusion length of 25 mm and a wire diameter of 1.2 mm, the wire melting amount per minute is 265 g / m.
The average weight of the transferred droplets is reduced to 32 mg, and the pulse frequency range for this welding method is 966 Hz or more.

If the base period is long, a short circuit occurs,
The average base time (T _b : FIG. 1)
Is preferably 1.0 ms or less. However, if the average base period is less than 0.15 ms, no vibration is given to the droplet. Smooth droplet transfer cannot be obtained. Therefore,
Average basis time (T _b) is 0.15ms more, it is desirable to be about 1.0 ms or less. More preferably, it is 0.3 to 0.5 ms.

As for the pulse conditions for the average current, by setting the peak current to (Average current × 1.3) A or more and the base current to 150 A or less, the droplets can be more effectively miniaturized and short-circuited during the base period. This makes it possible to stably transfer droplets during the peak period.

Next, the reason for limiting the wire composition according to the present invention, which is necessary to realize the ideal droplet transfer described above, will be described. C: 0.15 mass% or less C is an important additional element for securing the strength of the weld metal, but on the other hand, it lowers the viscosity of the molten steel and improves the fluidity. If the content exceeds 0.15 mass%, the behavior of the droplet and the molten pool during CO ₂ pulse welding becomes unstable, and spatter occurs frequently. Therefore, the C content is set to 0.15 mass% or less.

Si: 0.3 to 2.0 mass% or less Si is used as a deoxidizing agent, at least 0.3 mass% for obtaining high strength and high toughness, and for ensuring workability.
Need. Also, the amount of spatter in pulse welding tends to decrease slightly with the increase in Si. However, if the content exceeds 2.0 mass%, the slag content increases and the toughness of the weld metal decreases, so the upper limit of the Si content was set to 2.0 mass%.

Mn: 0.50 to 2.5 mass% or less Mn is a useful element as a deoxidizing agent and for obtaining high strength and high toughness. Its effect can be obtained by containing 0.50 mass% or more. Also, the amount of spatter in pulse welding tends to decrease slightly with an increase in Mn. However, if it is contained in a large amount exceeding 2.5 mass%, the slag removability deteriorates and the toughness of the weld metal decreases, so the upper limit of the Mn content was set to 2.5 mass%.

Ti: 0.15 to 0.30 mass% Ti is an element useful as a deoxidizing material and for securing the strength and weather resistance of the weld metal. Further, with regard to the transfer of the droplet, it has the function of increasing the viscosity of the droplet and suppressing the unstable behavior. FIG. 2 shows the results of examining the amount of Ti in the wire, the number of transitions of the droplet in pulse welding, and the relationship between the number of transitions and the average droplet weight calculated from the melting speed of the wire. Average current: 30 for normal pulseless welding
The droplet weight at 0 A is 58-62 regardless of wire composition.
In contrast to mg, it can be seen that the droplet can be made finer by adding Ti. However, Ti in the wire
If the amount is less than 0.15 mass%, the effect of the droplet is stable and fine, and the effect of suppressing spatter is poor.
If added in excess of ss%, not only will a convex bead be formed, but also the slag removability and the toughness of the weld metal will deteriorate, so the Ti content was limited to the range of 0.15 to 0.30 mass%.

S: 0.030 mass% or less S has a function of lowering the viscosity of the molten metal and assisting the detachment of the droplet suspended from the tip of the wire. However, 0.03
If it is added in excess of 0 mass%, the behavior of the droplet and the molten pool during pulse welding becomes unstable, and not only the spatter of small grains increases, but also the toughness of the weld metal decreases. Therefore,
The amount of S was limited to 0.030 mass% or less.

Ca: 0.0015 mass% or less Ca has the effect of contracting the arc and inhibiting the spraying of droplet transfer, but if the content exceeds 0.0015 mass%, the droplets and the molten pool during pulse welding become less effective. The behavior becomes unstable, and the spatter of large grains increases. Therefore, the amount of Ca is 0.00
It was limited to 15 mass% or less.

K: 0.0001 to 0.0030 wtmass% K has an effect of drastically reducing spatter in a very small amount. In particular, it is effective for stabilizing the behavior of droplets and molten pools during pulsed CO ₂ welding. However, if the content is less than 0.0001 mass%, the effect of reducing spatter is poor, while the content is 0.0030 mass%.
If the length exceeds the arc length, the arc length becomes long, the droplet suspended at the wire tip becomes unstable, and the spatter of large grains near the bead increases. Therefore, the content of K is set in the range of 0.0001 to 0.0030 mass%. Since K has a boiling point of about 760 ° C. and the yield in the molten steel stage is extremely low, it is extremely difficult to make K exist in the wire. However, it is advantageous to use thermal diffusion during the manufacturing process described later. Can be provided.

B: 0.0003 to 0.0030 mass% B, like K, has an effect of drastically reducing spatter in a very small amount. It is particularly effective in stabilizing the behavior of droplets and molten pools during pulsed CO ₂ welding. However, the content is 0.
If it is less than 0003 mass%, the effect of reducing spatter is poor, while
When added in excess of 0.0030 mass%, the toughness of the weld metal is reduced, so that B is contained in the range of 0.0003 to 0.0030 mass%.

Although the basic components have been described above, the following elements can be added as required in the present invention. Al: 0.50 mass% Al is added as necessary as a deoxidizing material and for the purpose of securing the strength and the weather resistance of the weld metal. Also,
Regarding the transfer of droplets, similarly to Ti, there is an effect that the arc is spread, the unstable behavior of the droplets due to the application of a high pulse current is suppressed, and the sputtering of small particles is suppressed. However, when the content exceeds 0.50 mass%, not only does the toughness of the weld metal decrease, but also the slag removability decreases.
mass% or less.

Cr: 0.60 mass% or less, Ni: 3.0 mass% or less, Cu: 3.0 mass% or less, Mo: 0.50 mass% or less All of Cr, Ni, Cu and Mo improve the strength and weather resistance of the weld metal. Is useful element and can be appropriately added as needed. However, since excessive addition causes a decrease in toughness, the content is set in the above range in either case of single addition or composite addition.

At least one selected from Nb, Zr, and V: 0.25 mass% or less All of Nb, Zr, and V are added as necessary for the purpose of securing the strength of the weld metal and the weather resistance. Can be. However, since an excessive addition causes a decrease in toughness, they are contained in a total amount of 0.25 mass% or less.

Other unavoidable impurities are as follows. O is an element inevitably mixed into the wire due to internal oxidation during steelmaking and the manufacturing process.However, since excessive addition lowers the toughness of the weld metal, it is 0.0025 ma.
It is preferable to suppress the content to ss% or less. Further, P and N are unavoidable impurities, and excessive incorporation causes a decrease in the toughness of the weld metal. Therefore, it is preferable to reduce these elements as much as possible.

The molten steel adjusted to the above-mentioned preferred composition is preferably made into a billet by continuous casting and then into a steel wire by hot rolling. Then, after cold-drawing by a dry method and annealing, it is subjected to pickling, copper plating and wire-drawing to obtain a product. In the present invention, the most stable method for adding K is to form an internal oxide layer on the surface layer of the wire by utilizing the annealing during the wire drawing step and to retain K in the internal oxide layer. is there. Because, as mentioned above, K has a boiling point of about 760 ° C and the yield in the molten steel stage is extremely low, so it is extremely difficult for K to be present in the wire. If K is used, K can be effectively added. In the other methods of holding by surface coating or plating, problems such as discoloration of plating are apt to occur, and the effect of reducing spatter by K is small because it is thermally unstable.

Factors that affect wire feedability, power supply stability, arc stability, welding workability, and the like include:
Other than the above, copper plating thickness, impurities such as copper powder adhering to the wire surface, wire drawing lubricant residue (Ca, Na) interposed between the wire metal surface and the copper plating layer, ratio of wire The surface area, the eccentricity of the wire, and the like can be considered. here,
The specific surface area is, for example, a geometrical relationship (eg, wire cross-sectional outer peripheral length × wire longitudinal length) assuming that there is no actual surface area including fine irregularities (fluctuations in the height direction) of the wire surface by SEM image processing and the irregularities. Is the ratio of the theoretical surface area derived in the formula (1), and the eccentricity of the wire is the maximum value d _max , the minimum value d _min , and the 10-point average value d of the wire diameter.
_{From ave} , it is calculated by (d _max -d _min ) / d _ave .

Regarding these factors, the copper plating thickness is 1.5
μm or less, impurities such as copper powder should be 0.2 g or less per 10 kg of wire, wire lubricant residue (Ca, Na) should be 5 ppm or less, specific surface area of wire should be 1.02 or less, and eccentricity of wire should be 0.008 or less. preferable.

[0031]

EXAMPLE 1 Continuously cast steel material (billet) was hot-rolled to 5.5 mm.
After making a wire of φ, the wire diameter is 2.8mm by cold drawing using a drawing lubricant containing calcium carbonate and CaO as main components.
φ, and then a 5 to 15% aqueous solution of 3 potassium citrate was applied. Dew point: -5 ° C or less, oxygen: 100 ppm or less,
Carbon dioxide: heated to 750-850 ° C. in an N ₂ atmosphere of 0.05% or less. At this time, by adjusting the potassium salt concentration, the heating temperature and the heating time, the amount of oxygen and the amount of potassium due to the internal oxidation of the wire were adjusted. Next, the steel wire was changed to 15% H at 35 ° C.
After immersion in a Cl solution for 20 seconds, water washing, Cu plating, cold drawing to 1.2 mmφ
The wire coated with 0.8 g of lubricating oil was subjected to a welding test.
The tensile strength of the wire is 850 to 980 MPa, and the Cu plating thickness is 0,0.
20 to 0.75 μm, impurities such as copper powder adhering to the wire surface are 0.05 g or less per 10 kg of wire, and residue of wire drawing lubricant is C
a: 1 ppm or less, Na: 1 ppm or less, and non-surface area is 1.
The eccentricity was 005 or less and the eccentricity was 0.003 or less. In Tables 1 and 2,
The composition of the components of the prototype steel wire is shown. In addition, Cu in the composition
Is a value including plating.

[0032]

[Table 1]

[0033]

[Table 2]

Using the steel wires shown in Tables 1 and 2, bead-on welding was performed, and the amount of spatter generated at that time was examined. The welding conditions are as follows. 100% CO ₂ per minute: 20 L as shielding gas, welding current: 300 A, voltage: 34 V, welding speed: 40 cm /
Under the condition of min, bead-on welding was performed on a steel plate having a thickness of 19 mm. The pulse conditions at this time were: the number of pulses per droplet transfer: 8 to 15, the peak current: 500 A, the base current: 80 A, and the average base period was 0.4 ms (frequency: 467 Hz). Table 3 summarizes these welding conditions.

[0035]

[Table 3]

The target value of the spatter generation amount is 1.2 g / m
set to in or less. In particular, good for less than 1.0 g / min (以下), acceptable for more than 1.0 g / min and less than 1.2 g / min (△), 1.
A value exceeding 2 g / min was judged as unacceptable (x). Table 4 shows the obtained survey results. FIG. 3 shows the relationship between the Ti content and the amount of spatter generated.

[0037]

[Table 4]

As is clear from Table 4 and FIG. 3, when a steel wire having a component composition satisfying the proper range of the present invention was used, the amount of spatter generated was significantly reduced. . In particular, when K is contained in an amount of 1 to 30 ppm or B is contained in an amount of 3 to 30 ppm, a further reduction in sputtering is achieved. In contrast, C,
In all of the comparative examples (Nos. 31 to 36) in which any of the S, Ca and Ti contents were out of the proper range of the present invention, a large amount of spatter occurred in excess of 1.2 g / min.

Example 2 In this experiment, the welding conditions were changed as follows.・ Welding conditions Shielding gas: 100% CO ₂ (25 L / min) ・ Pulse power supply Welding current: 400 A Voltage: 37 V Welding speed: 50 cm / min ・ Steel plate thickness: 22 mm ・ Pulse condition Number of pulses per droplet transfer : 7 to 13 Peak current: 550 A Base current: 150 A Average base period: 0.35 ms ・ Frequency: 885 Hz These welding conditions are summarized in Table 5.

[0040]

[Table 5]

In this example, the target value of the amount of spatter was set at 1.0 g / min or less. And especially 0.8 g / m
In less than or equal to good (○), 0.80 g / min or more and 1.0 g / min or less were acceptable (△), and 1.0 g / min or more was unacceptable (×). Table 6 shows the obtained survey results. FIG. 4 shows the relationship between the Ti content and the amount of spatter generated.

[0042]

[Table 6]

As is clear from Table 6 and FIG. 4, when a steel wire having a component composition satisfying the proper range of the present invention was used, the amount of spatter generated was significantly reduced. . In particular, when K is contained in an amount of 1 to 30 ppm or B is contained in an amount of 3 to 30 ppm, a further reduction in sputtering is achieved. On the other hand, in each of the comparative examples (Nos. 31 to 36) in which the component composition was out of the proper range of the present invention, a large amount of spatter occurred in excess of 1.0 g / min.

[0044]

Thus, according to the present invention, the pulse C
In O ₂ welding, not only the arc stability can be improved, but also the amount of spatter generated can be significantly reduced, and as a result, high quality welding can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an output state of a pulse.

FIG. 2 is a graph showing the relationship between the amount of Ti in a wire, the number of times of transfer of droplets in pulse welding, and the average weight of melting.

FIG. 3 is a graph showing the relationship between the amount of Ti in a wire and the amount of spatter generated in Example 1.

FIG. 4 is a graph showing the relationship between the amount of Ti in a wire and the amount of spatter generated in Example 2.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 38/14 C22C 38/14 (72) Inventor Koichi Yasuda 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki F-term (Reference) in Technical Research Laboratory, Steel Works 4E001 AA03 BB09 DD04 EA05 4E082 AA03 AB02 BA04 DA01 EA02 EA06 EA11

Claims (3)

[Claims] 1. A pulse CO ₂ welding wire for applying 7 or more pulses per droplet transfer, wherein C: 0.15 mass% or less, Si: 0.3 to 2.0 mass%, Mn: 0.5 to 2.5 mass%. , Ti: include 0.15~0.30mass%, and S: 0.030 mass% or less, Ca: limit below 0.0015%, the balance pulse CO ₂ welding, characterized by comprising the composition of Fe and unavoidable impurities Steel wire. 2. A wire for pulse CO ₂ welding imparting one droplet or migration per 7 pulses, C in mass%: 0.15 mass% or less, Si: 0.3 ~2.0 mass%, Mn: 0.5 ~ Contains 2.5 mass%, Ti: 0.15 ~ 0.30mass%, K: 0.0001 ~ 0.0030mass% and B: 0.0003 ~ 0.0030mass%, contains one or two kinds, and S: 0.030 mass% or less , Ca: 0.0015 mass% or less, the balance being Fe and unavoidable impurities, a steel wire for pulse CO ₂ welding. 3. The steel wire for pulse CO ₂ welding according to claim 1, wherein the steel wire has a composition further containing Al: 0.50 mass% or less.