JPS62296993A - Steel wire for mag pulse high speed welding - Google Patents

Abstract

PURPOSE:To enable welding with the decreased generation of spatters in MAG pulse welding by incorporating specific ratios of C, Si, Mn and S into the titled wire, consisting the balance of iron and impurity elements, incorporating specific ratios of Ti, Al, N and O into the impurity elements and specifying a parameter and Mn/Si ratio within the range of specific values. CONSTITUTION:The compsn. of the wire for MAG pulse high-speed welding is composed of 0.03-0.15wt% C, 0.1-0.75 Si, 0.2-1.5% Mn, 0.005-0.03% S and the balance iron and inevitable impurity elements. The inevitable impurity elements are composed of <=0.05% Ti, <=0.01% Al, <=0.015% N, and <=0.015% O. The parameter K expressed by the relation is so determined as to satisfy the range of 0.04-0.15 and the Mn/Si ratio of 1-10. Defectless beads are obtd. and the welding with the extremely decreased generation of the spatters in executed by using such wire for MAG pulse high speed welding.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a steel wire that generates less splinters and ivy in high-speed MAG welding using a pulsed power source.

(Conventional technology) Inductive welding (gas metal arc using a relatively small diameter wire) is a welding method suitable for high-speed welding because of its high current density and good arc concentration, especially in combination with welding robots. It is used.

With the spread of welding robots, there is a growing trend toward higher efficiency and faster welding, and there is a strong demand for stable, high-speed welding.

However, conventionally, high-speed welding has had two major problems: spatter generation and bead formation.

Spatter not only adheres to the base metal and welding torch, impairing efficiency and shielding performance, but also invades robots, peripheral equipment, and jigs, and impairs their smooth operation.

There are various factors that can be considered to cause this spatter, but
The greatest influence is caused by contact short-circuiting when droplets grow and transfer to the molten pool, and are scattered by arc force and pinch force during the process of arc recirculation.

Therefore, it is considered effective to reduce spatter by keeping the arc long enough to prevent short circuits.

On the other hand, if the welding speed is increased while the arc length remains long,
Undercuts are likely to occur, and bead formation such as humping beads and arc breaks may occur at high speeds.

In order to suppress the occurrence of spatter while ensuring bead forming properties as described above, it is necessary to make the arc length as small as possible to the extent that short circuits do not occur.

Since the arc length without short circuit depends on the diameter of the transferred droplet, measures are taken to increase the number of droplet transfers, and Ar-Co□ (generally about 20% CO□) is used as a shielding gas. Ratio) MA using pulsed power supply with mixed gas
Considerable effects have been achieved by G-pulse welding.

However, even in MAG pulse welding, the welding speed at which a good bead can be obtained in a non-short circuit region is about 50 to 80 cm/mjn.

On the other hand, as a measure against the amount of spatter generated in the event of a short circuit, a means of adjusting the secondary inductance of the welding power source was proposed in the Japanese Patent Publication No. 47-1983.
This has been done in the technology described in Japanese Patent No. 41659, etc., but in pulse power supplies, the rise and fall times of the pulse waveform become long, which limits the increase in inductance, so this is only done to a minimum. A large amount of spatter is generated during a short circuit.

As detailed above, although individual measures have been taken to address the two major problems in high-speed welding, bead formation and spatter, none of them are sufficient, and even more so, no means have been taken to solve both at the same time. .

(Problems to be Solved by the Invention) In view of the current situation, the present invention aims to achieve bead formation properties and spatter reduction in high-speed welding at the same time.
Focusing on the short-circuit phenomenon in short-circuit transition welding using an AG pulsed power source, we conducted a detailed study on the relationship between short-circuit characteristics and wire components.As a result, we adjusted the wire components and determined the control parameters and frequency characteristics of the pulsed power source that depend on these components. MAG which suppresses the amount of spatter generated during short circuit and also satisfies high-speed welding performance by matching
The present invention provides a steel wire for pulsed speed welding.

(Means for Solving the Problems) The gist of the present invention is that the elements in the wire are: C: 0.03 to 0.15%, Si: Q, 1
~0.7%, Mn: 0.2-1.5%, S: 0.0
05 to 0.03%, balance consisting of iron and unavoidable impurity elements, and among the unavoidable impurity elements, Ti: 0.05% or less, Ar: 0.01% or less, N: O, 0.015% or less,
0: 0.015% or less, the parameter (K) shown by the following formula is in the range of 0.04 to 0.15, and Mn
/Si ratio is 1 to 10.
In steel wire for pulsed high speed welding.

K=C-0,06X5i-0,O7XMn+4xS+3
x N -0,2x O However, the element symbol indicates the content (weight %) of the element.

The present invention will be explained in detail below.

(Function) Figure 1 shows JIS Z3312 YGW15 series wire (
Diameter 1, 2n+φ, C: 0.10%, Si: 0.80
%, Mn: 1.20%, P: 0.010%, S:
0.003%, Cu: 0.20%, A i: 0.
005%, Ti: 0.10%) and a pulse power supply, shielding gas Δr-20%CO□, welding current: i6o
, 25OA, welding speed: 150-200 cm/min
, Pulse frequency: 110, 22011z, downward welding (Bead on plate) was performed, the arc length was changed by changing the welding voltage from 18 to 28V, and the amount of spatter sampled was calculated by the number of short circuits (times/5ea).
).

The measured values are included in the range between the two straight lines in the figure. The number of short circuits in this case was determined by recording changes in welding voltage on a data recorder, and counting the number of short circuits when the instantaneous value of the voltage was 10 V or less.

The increase in spatter amount has a linear relationship with the number of short circuits, indicating that the main cause of spatter generation is short circuits.

Figure 2 shows the welding current (1 ) and welding speed (U). Compared to range A when the voltage is kept as low as possible and the arc length is shortened, the favorable condition range when the arc length is increased to 100 times/second or less is significantly narrower, resulting in lower current and lower speed. It's on the side.

In this way, even in MAG welding using a pulsed power source,
In order to ensure bead formation at high speed, it is necessary to select conditions where the arc length is sufficiently short and spatter occurs.

Incidentally, in FIG. 1, the inventors of the present invention have noticed that there is a large difference in the amount of spatter generated even when the number of short circuits is the same.

In both cases, the number of short circuits and the amount of spatter show a nearly linear proportional relationship, so there is no large variation in the amount of spatter generated for each short circuit, and it is thought that the generation patterns are different, so a detailed study of the short circuit mechanism was conducted.

Figure 3 shows the same wire and shielding gas as in Figure 1, using an inverter-controlled pulse power supply that allows frequency adjustment over a wider range than conventional power supplies with fixed frequencies at the same wire feeding speed. In combination, this shows an example of the results of examining the frequency and amount of sputtering.

In this case, the wire feeding speed was 7 m/min, the welding speed was 150 cm/min, and Ext (chip-
Distance between base metals) is 18 Tsuru, downward welding current is 210-220
A1 voltage is 22-23V.

A relationship was obtained in which the amount of sputtering rapidly decreased as the frequency was increased from point A, reached a minimum at point 0 (hereinafter referred to as the appropriate frequency), and increased again above this point. Therefore, we investigated the reason why the amount of spatter generated by the same short circuit differs depending on the frequency, and found that at the appropriate frequency (0 point), the short circuit ends during the base current period of the pulse cycle and the arc regenerates (base On the other hand, at point B on the low frequency side, arc re-occurrence (falling short circuit) is more likely to occur during the falling period of the peak current, and on the high frequency side At point D, there was a tendency for a peak rise short circuit.

In normal pulsed MAG welding, in which the arc length is maintained sufficiently to prevent short circuits, a pinch force acts near the contact interface between the weld and the solid wire, which is generated by melting the wire during pulsed current, resulting in rapid constriction growth. A cycle in which the droplet detaches and flies due to the axial force and transfers to the base material is performed stably with each pulse. However, under short arc length conditions, what is the power/density effect of the above cycle? Since the melting tube is short-circuited, the shape and current value of the droplet at the time of the short-circuit, as well as the current value during arc regeneration, will have various effects on the droplet. If arc regeneration occurs when the current is sufficiently large, a large force will act on the molten part and pool at the tip of the wire, significantly impairing bead formation and causing spatter. If the area of the droplet tip contact area is smaller than the minimum cross-sectional area of the droplet, pinch force will concentrate on this contact area, increasing spatter.

Therefore, as a short circuit condition to minimize spatter, i
) Perform short circuit and arc regeneration with as small a current as possible.

ii) The minimum diameter part of the droplet at the time of short circuit must be other than the contact area, that is, the droplet-wire solid part, and the 0 point in Figure 3 is considered to be the point that satisfies these two conditions. It will be done.

By the way, if a stable base short circuit is performed at this 0 point in synchronization with the pulse frequency, the appropriate frequency will depend on the physical properties of the droplet (interfacial tension, viscosity, etc.) and will depend on the wire components. Therefore, we thought that increasing the frequency would make the droplets finer, shorten the arc length, lead to stable short-circuit transition, and eventually lead to smaller particles and less spatter.

Therefore, using wires of various compositions, the appropriate frequency was determined under the same welding conditions as in the case of Fig. 3, and the influence of the wire component on the amount of spatter at the appropriate frequency was replaced by the equivalent of C, which was the parameter (K). That is, K=C-0,0
6xSi o, o 7 XMn+ 4xS+3XN-
It is indicated by 0.2X○ (however, the element symbol is the weight percent content of the element), and it has become possible to limit the range in which the amount of sputtering is small to this value. The relationship between the K value and the amount of sputtering is as shown by diagonal lines in FIG.

That is, when the K value is 0.04 or less, the amount of sputtering increases, and when the K value is higher than this, the sputtering tends to decrease little by little as K increases, but when it is 0.15 or higher, it increases again, so the value is 0. It is limited to a range of 0.04 to 0.15. The amount of sputtering increases below 0.04 because l
As the diameter of the droplet transferred by the pulse increases, the chance of contact with the molten pool increases during the growth process of the droplet, and it is thought that the conditions for optimal short circuit described above cannot be satisfied.
, 15 or more, the pulse base time becomes short and the frequency of not being able to complete the short circuit within the base period becomes uniform.

In addition, as an attempt to correlate the K value with the physical properties of the wire, we measured the interfacial tension (γ) of the molten wire for several types of wires used, and found that Si, Mn, S, and 0 are elements that reduce γ, while C, Ti is an element that increases the K value, and for C1Si+Mn and O, which are the majority of the elements constituting the K value, the tendency of increase and decrease of each element with respect to the value was consistent. (Interfacial tension measurement method SessilSe55ileDro
p (sessile drop method), atmosphere: Ar, temperature 1515-16
00° C.) In the present invention, in addition to the above-mentioned limitations, the Mn/Si ratio is limited. FIG. 5 shows the relationship between the Mn/Si ratio and the sputter-generated 'Jeffi' of a wire in which C25i+ Mn+ S, T+, 81N, and O are each within the limited range of the present invention, and the K value is also within the range of the present invention. This shows the relationship. (The welding conditions are the same as in FIG. 3.) When the Mn/Si ratio exceeds 1 to 10, a phenomenon in which the amount of spatter increases significantly is observed.

Therefore, in the present invention, the Mn/Sz ratio is limited to a range of 1 to 10. Within this range, the upper limit of the amount of sputtering tends to be low, although it is small at about 4 to 6, which is the most preferable range.

Although the reason for this phenomenon is not necessarily clear, it is thought that the viscosity of the molten metal and the arc stability are mutually involved. That is, the addition of Sf is known to increase the viscosity coefficient of the molten steel heavy metal, and acts in the direction of lengthening the time required for separation when the viscosity increases and transfers to the former droplets. On the other hand, Mn is an element with high metal vapor pressure in the arc. Therefore, it is thought that as the Mn/Si ratio decreases, the time required for droplet separation and migration increases and the frequency of exceeding the pulse base period increases, and within the wire composition range of the present invention, the limit is Mn
/Si ratio is close to 1. In addition, as the Mn/Si ratio increases, arc stability is affected by vapor pressure during the process of arc regeneration from short circuit, which increases arc length fluctuations and is thought to increase variation in droplet migration time. .

These phenomena were also read from the oscillograph that recorded the arc voltage.

Next, the reasons for limiting the wire components of the present invention will be described.

C is an effective element for reducing spatter because it makes the droplets finer and shifts the appropriate frequency to the higher frequency side, but it also has the effect of hardening the welding metal, making it difficult to meet the conditions of high-speed welding. If it exceeds 0.15%, there is a risk of cracking, so the upper limit was set. Moreover, if it is less than 0.03%, not only will the effect of reducing spatter not occur, but also the deoxidizing effect cannot be expected.

In normal welding, Si is added in an appropriate amount as a deoxidizing element to ensure the toughness of the weld metal, but in the present invention, as mentioned above, it has the effect of increasing the viscosity of the droplet and increasing spatter, so a lower amount is preferable. However, if it is less than 0.1%, deoxidation will be insufficient even during high-speed welding, and bubbles will occur in the weld metal. Moreover, if it exceeds 0.7%, it will not have an adverse effect on spatter reduction, so it was set as the upper limit.

Regarding Mn, the effect is as described above, and the lower the content, the better, but if it is less than 0.2%, the pore resistance will deteriorate and the bead shape will be poor, so the lower limit was set at 0.2%.

Moreover, since the hardness of the bead increases rapidly when Mn exceeds 1.5%, the upper limit of Mn was set at 1.5%.

S is not only effective in shifting the appropriate frequency to the high frequency side and reducing spattering, but also has the effect of improving the bead shape, so it is desirable to add a large amount, but it is also an element that induces high temperature cracking, and there is a conflict with the amount of Mn added. The upper limit was set at 0.03%. If the content is less than the lower limit of 0.005%, no improvement effect on spuck and bead shapes will be observed at all.

Ti is a strong deoxidizing element and forms a thin slag on the surface of the droplet, which limits the arc generation point, increases the variation in droplet transfer time, and significantly increases spatter.
．． If the content is less than 0.05%, this effect is small, so the upper limit of the impurities was set here.

Since Aβ also has the same effect as Ti and increases sputtering even in a small amount, the content was set to 0.01% or less.

The level of N as an impurity in the wire varies depending on the melting method and other conditions. For example, in the electric furnace melting method, the level of N is 0.02
It may be mixed up to about 0%. In the present invention, the effect of N on spatter is preferably at a higher level, but in high-speed welding, N is the main cause of blowholes in the weld metal, so the upper limit is set at 0.015%.

0 is 0.03 to 0.0 when it is contained in the wire as oxide inclusions such as St, Mn+ Tit A1, etc., or as impurities in the scale layer on the wire surface or coating oils and fats.
It exists up to about 0.04%. However, although it does have a detrimental effect on high-speed weldability and spatter, the extent of this is small, so it was set at the normal level of 0.015% or less.

The reasons for limiting the wire components of the present invention have been explained in detail above, but other components such as Ni, Cr, and Mo have little effect on sputtering and do not need to be added in particular. % is permissible. Further, there is no restriction on the amount of Cu added, but although steel wires are usually plated with copper in many cases, this amount is sufficiently permissible.

The effects of the present invention will be explained in more detail below using Examples.

(Example) A steel ingot obtained by melting is forged, rolled, wire-drawn, and plated (C
Using the 31 types of wires shown in Table 1 that were finished into wires of 1.2 n + φ through each step of u), high-speed welding was performed on the steel plates shown in Table 2 under the welding conditions shown in Table 3. Table 4 shows the results of an investigation regarding the amount of spatter collected, bead appearance, X-ray performance, arc stability, and appropriate frequency.

The bead appearance should be free of undercuts and bead irregularities.
For X-ray performance, those with no blowholes or bits were considered good, and for arc stability, those with no arc breakage or arc instability were evaluated as good.

Wires 1 to 20 show wires of the present invention, and numbers 21 to 31 show comparative examples. Nf121. N124 wire is C,S
Although chemical components such as I'In, T+, AJ N, and O, and Mn/Si are within the scope of the present invention, their K values are outside the range, so the bead appearance, X-ray performance,
Arc stability etc. are good, but the amount of spatter is large.

Since the 11k1221127 wire is out of the Mn/Si range, the bead formation properties such as bead appearance are good, but the amount of sputtering is large. Wire No. 23 had a carbon content below the lower limit, and the amount of spatter was slightly larger than the wire of the present invention, but many blowholes occurred and the bead appearance deteriorated. The N25 wire had an N content exceeding the upper limit of the range, and many blowholes were observed in the X-ray transmission test. Each of the 28 wires on the 26° floor had Si outside the range, but the bead appearance, X-ray performance, and arc stability were good in wire 26, but spatter occurred frequently. Room 2
In No. 8, not only blowholes were observed due to insufficient deoxidation, but also the bead appearance and arc stability were poor, and the bead forming property was significantly deteriorated. Since the Hiroshi 29 wire contains too much Ti, the amount of sputtering increases. Since the black wires 30 and 31 have an Mn/Si ratio of 1 or less and are outside the range, the amount of sputtering is significantly increased in both cases.

As described above, wires that are outside the scope of the present invention are unable to simultaneously satisfy sputtering properties and bead forming properties.

Table 4 Welding Results (Effects of the Invention) As described above, according to the present invention, when used in MAG pulse high speed welding, not only can healthy bead formation be obtained, but also welding with an extremely small amount of buffing can be achieved. We can provide steel wire for MAG pulsed high-speed welding that enables
The present invention has enormous industrial benefits.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the number of short circuits and the amount of spatter, Figure 2 is a graph showing the relationship between welding speed and welding current in horizontal lap fillet welding, and Figure 3 is a graph showing the relationship between pulse frequency and amount of spatter. , FIG. 4 is a graph showing the relationship between the value and the amount of sputtering, and FIG. 5 is a graph showing the relationship between Mn/Si and the amount of sputtering. Figure 1 Party 4 each four numbers (Yonoectsu Figure 2; g power, 9 Z (A) Okayama break'l:, <Hz) Figure 5

Claims (1)

[Claims] C: 0.03 to 0.15% (weight %, same hereinafter), Si
: 0.1 to 0.7%, Mn: 0.2 to 1.5%, S: 0.005 to 0.03%, the balance consists of iron and inevitable impurity elements, and among the inevitable impurity elements, Ti: 0 .05% or less, Al: 0.01% or less, N: 0.015% or less, O: 0.015% or less, and the parameter (K) represented by the following formula is 0.04 to 0.05%.
15 and a Mn/Si ratio of 1 to 10. K=C-0.06×Si-0.07×Mn+4×S+3
×N−0.2×O However, the element symbol indicates the content (weight %) of the element.