JPH0484689A - Gas shielded arc welding wire - Google Patents

Abstract

PURPOSE:To produce the welding wire which yields a defectless weld metal which hardly generates defects, such as pits and blowholes by preparing the gas shielded arc welding wire consisting of a specific compsn. regulated in respective contents of C, Si, Mn, Al, and Ti. CONSTITUTION:The gas shielded arc welding wire contg., by weight %, 0.15 to 0.30% C, 0.05 to 0.50% Si, 0.20 to 1.00% Mn, <=0.030% P, <=0.030% S, 0.020 to 0.200% total of one or two kinds of Al, and Ti, and 0.020 to 0.200% total of one or two kinds of Bi and Sb and the balance Fe and unavoidable impurities is prepd. This wire is produced by rolling and drawing a steel ingot in the same manner as for ordinary wires and subjecting at need the wire to copper plating. The generation of the pits is obviated and the generation of the blowholes is extremely lessened even if galvanized steel sheets are welded at a high speed by using a shielding gas. The welded steel sheet which is sufficiently satisfactory for structural purposes is obtd.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention is characterized in that defects such as pits and blowholes are less likely to occur when gas-shielded arc welding is performed on steel plates that have been previously subjected to anti-rust treatment, such as galvanized steel plates. This invention relates to a gas-shielded arc welding wire that produces sound weld metal.

(Prior Art) Examples of steel materials with excellent corrosion resistance that have been subjected to antirust treatment include galvanized steel sheets. Galvanized steel sheets are ordinary hot-rolled or cold-rolled steel surfaces that are galvanized, and are mainly used in the field of thin sheets, such as roofing sheets and other building materials, gasoline cans, and washing machine parts. It tends to be used in many other automobile bodies as well.

When welding galvanized steel materials, zinc with a boiling point (906°C) lower than the melting point of iron enters the droplets or molten pool from the surface of the steel material during welding, and the zinc vapor bumps and entrains the atmosphere, causing welding problems. During the metal solidification process, it does not float completely and remains as bubbles, resulting in frequent defects such as pits and blowholes. In particular, gas shield welding using solid wire, which is most commonly applied to welding thin plates, is significantly susceptible to the effects of zinc.

Generally, in gas shielded arc welding, the welding speed is 1m/
If it exceeds min, the gas shielding property deteriorates, air is likely to be drawn into the welding atmosphere, a large amount of nitrogen gas is absorbed, and defects such as pits and blowholes are likely to occur.

Furthermore, when welding thin plates, the shape of the joint is likely to be affected by the surface of the steel plate due to overlapping fillets, etc., making it easy for defects to occur.

An effective way to reduce the harm caused by zinc is to mechanically remove zinc from the weld line in advance.
It is time consuming and inefficient.

As a defect prevention technology for pits and blowholes in galvanized steel sheets, Japanese Patent Application Laid-Open No. 64-57979 discloses a solid wire containing 0.10 to 1.00% Mo with basic components of C, Si, Mn, and MO. A welding material is disclosed. However, since the solid wire with such a composition contains a large amount of Mo, the cost of raw materials becomes high, and no economic effect can be expected.

(Problems to be Solved by the Invention) The present invention eliminates the occurrence of defects such as pits and blowholes, which are problems in gas-shielded arc welding of galvanized steel plates and other materials that are welded at high speeds, to an extent that does not cause any practical problems. It provides a gas-shielded arc welding wire that is as small as possible.

(Means for solving problems) The gist of the invention is C: 0.15-0.30% by weight.

Si; 0.05-0.50%, Mn・0.20-1
．． 00%, P, 0.030% or less, S; 0. (
130% or less, Al1. Total of one or two of Ti: o, 020-0.200%, Total of one or two of Bi, Sb: o, 020-0.200
%, with the remainder consisting of Fe and unavoidable impurities.

[For production]

As mentioned above, the present inventors believe that the reasons why pits and blowholes are particularly likely to occur in galvanized steel sheets in gas-shielded arc welding are: (a) bumping of zinc during welding promotes air entrainment; , Since the zinc that has entered the molten weld metal cannot be dissolved into the iron (and has a low boiling point, the molten metal remains in a vapor state even during the solidification process, and this remains and forms bubbles. (b) Shielding properties during high-speed welding Because of this, air is easily drawn into the welding atmosphere and nitrogen is easily absorbed into the molten metal.On the other hand, in high-speed welding, the solidification rate is fast, so not only the gasified zinc but also nitrogen gas in the molten weld metal is absorbed. (c) In gas-shielded arc welding, elements with strong deoxidizing power such as Si, Mn, AA', and Ti are added to obtain clean weld metal. However, it was considered that if the deoxidizing effect is strengthened too much, the molten zinc will not be oxidized and will remain as bubbles, promoting (a).

In order to reduce the effects of zinc and nitrogen and prevent pits and blowholes, it is necessary to increase the oxygen potential of the molten pool by minimizing the amount of elements with strong deoxidizing power (al).
Converts harmful zinc vapor into zinc oxide ZnO with a high melting point and slags it off. (bl) Lowers the viscosity of molten metal by increasing the oxygen potential of the molten pool, making it easier to release zinc vapor and nitrogen gas through stirring action. ( C) CO and B are removed from the droplet surface during the droplet transfer stage.
(d) suppressing zinc and nitrogen that try to enter the droplet from the surroundings by actively blowing out i or sb;
We considered that it would be effective to fix the nitrogen that had entered the molten pool, and from this point of view, we investigated the wire composition and came up with the present invention.

That is, the conventional gas shielded arc welding wire is made of Si, M
n, A1. An element with strong deoxidizing power such as Ti is added to promote a deoxidizing reaction in the molten pool to obtain clean weld metal. However, the deoxidation reaction during high-speed welding occurs because the droplets are rapidly cooled in the molten pool, and is thought to occur during the droplet transfer stage in the arc column at a high temperature above the molten pool temperature. In this case, the main deoxidizing reaction is thought to be C+O→CO, and the main deoxidizing reaction is thought to be C in the wire.

Therefore, in the present invention, the oxidation reaction is improved by increasing the amount of C added to increase the 00 partial pressure around the droplet at the droplet transfer stage, and by adding appropriate amounts of Si, L, and Ti to optimize the oxidizing power of the weld metal. Activates the oxidation of zinc and promotes the oxidation of zinc, lowers the viscosity of the molten metal by increasing the oxygen potential by activating the oxidation, and facilitates gas release from the molten pool. ．． The combined effect of adding an appropriate amount of Ti and fixing nitrogen to the ground eliminates the occurrence of pits and suppresses the occurrence of blowholes.

In addition, although an appropriate amount of old+sb is added in the present invention, old and sb
Since the boiling point of zinc is slightly higher than the melting point of iron, it is blown out from inside the droplet during the droplet transfer stage, increasing the partial pressure of old and sb around the droplet as well as the 00 partial pressure mentioned above, and causing zinc to flow into the droplet. It suppresses the intrusion of nitrogen and nitrogen, and enhances the above actions and effects.

The reasons for limiting the components of the wire of the present invention will be described below.

By increasing the amount of C added, the 00 partial pressure around the droplet increases during the droplet transfer stage, activates the blowing of CO, and suppresses zinc and nitrogen that try to enter the droplet from the surrounding area.
Although it suppresses the occurrence of pit blowholes, C is Si,
It is determined based on the amount of addition of Mn, A 1 , and Ti, and the amount of addition of Si, Mn, and AjLTi of the present invention is 0.3.
Even if it exceeds 0%, pits will not occur much, but the wire drawability will deteriorate at the stage of processing into a wire, and the strength of the weld metal will further increase, so the upper limit was set at 0.30%. Also, if it is less than 0.15%, pits will occur frequently, so the lower limit was set at 0.15%.

Si and Mn are added as deoxidizing agents, but by adjusting the deoxidizing power to a slightly lower value, increasing the oxygen potential of the molten metal and promoting the oxidation of zinc, and lowering the viscosity of the molten metal to make it easier for gas to float. Used to suppress the occurrence of blowholes due to zinc. However, Si is 0.
If more than 1.00% of Mn is added, excessive deoxidation occurs and pits and blowholes occur frequently, so the upper limits were set to 0.50% for Si and 1.00% for Mn. Also S
If i is less than 0.05% and Mn is less than 0.20%, deoxidation is basically insufficient and pits and blowholes occur frequently, so the lower limits were set to 0.05% and 0.20%, respectively.

P and S are elements that inhibit cracking resistance, and it is preferable to suppress them as much as possible especially in the wire of the present invention in which a large amount of C is added, but the purpose is achieved if both are 0.030% or less. .

Al and Ti are used as deoxidizers together with 3i and Mn. Particularly in high-speed welding, shielding performance is reduced, air is drawn into the welding atmosphere, and the molten metal is likely to be significantly oxidized, resulting in insufficient deoxidation. Aj2. Adding a small amount of Ti is most effective in preventing excessive oxidation due to air entrainment without impairing the viscosity of the molten metal, but if the total amount of Ti or both is added in excess of 0.200%, deoxidation may occur. If it is excessive, it will cause a large amount of pits and blowholes, so the upper limit of the total of one or two types was set to 0.200%. Furthermore, if the total amount of one or two types is less than 0.020%, the deoxidizing effect will be insufficient and the integrity of the weld will be impaired, so the lower limit was set as 0.020% for the total of one or two types.

Since the boiling point of old and Sb is slightly higher than the melting point of iron, it is blown out from inside the droplet to the outside of the droplet during the droplet transfer stage, increasing the partial pressure of old and sb around the droplet along with the 00 partial pressure mentioned above, and causing the droplet to This suppresses zinc and nitrogen that try to enter the tank, preventing pimples and blowholes from forming. It is advantageous to have a large amount of Sb, but if the total amount of one or both of Sb and Sb is added in an amount exceeding 0.200%, the stability of the arc will be impaired and it will be difficult to form a sound weld bead. , the upper limit was set to 0.200% for the total of one or two types. Furthermore, if the total amount of one or both of [li and Sb is less than 0.020%, the effect of suppressing pits and blowholes will be weakened and they will occur frequently, so the lower limit was set to 0.020% for the total of one or two kinds.

In the present invention, the wire composition is designed to increase the oxygen potential of the molten pool by minimizing the amount of added elements with strong deoxidizing power.
It is advantageous to have more. However, if the amount of O is increased, when the wire material is drawn and finished as a wire, the surface of the wire is likely to be scratched, and rust is likely to occur starting from the scratches, reducing its function as a welding wire. Therefore, the upper limit of 0 is preferably 0.0070%.

The present invention is constructed as described above, but the wire raw material contains Ni.
, Cr, Cu, V, Nb, Ta, Zr,
Te, B, Ce, Ca, Sn, As.

It contains 0, N, and other metal elements as inevitable elements. In particular, Ni and Cr may be contained at about 0.10%, and the unavoidable elements other than Ni and Cr are 0.015%.
It may contain about %. However, with these amounts, there is no problem in preventing the formation of pits and blowholes.

Note that the wire of the present invention can be manufactured by rolling and drawing a steel ingot in the same manner as ordinary wires, and subjecting the wire to copper plating if necessary.

Even if a galvanized steel plate is welded at high speed using a wire with such a composition and a shielding gas containing CO2 or Ar mixed with CO□ or 02, there will be no pits and no blowholes. There is very little generation, and it is fully satisfactory for use in structures.

EXAMPLES Below, the effects of the present invention will be specifically explained with reference to Examples.

〔Example〕

Table 1 shows the number of pits and the rate of occurrence of blowholes in addition to the inventive wire and comparative wire (both have a diameter of 1.2 mm). Plated steel plate (thickness t =
2.0mm, width w = 50mm, length 1 = 30
As shown in Fig. 1, two sheets of 0 mm) were stacked vertically downward and overlapped fillet welding was performed, and the pits and blowholes generated at the fillet bead were compared. Table 2 shows the steel type and amount of galvanized steel sheets used for this vertical downward lap fillet welding, and Table 3 shows the welding conditions for the weld strips.

After welding was completed, the number of pits generated on the bead surface was visually counted, and then a radiographic test was conducted to investigate the occurrence of blowholes in the weld bead.

After counting the number of pits, calculate the number of pits generated per meter of bead (
It was evaluated as (number of pieces/m). In addition, the blowhole width in the longitudinal direction of the bead was measured using a radiographic test film, and the blowhole occurrence rate (%) was calculated from the total blowhole width with respect to the bead length.

In Table 1, wires N011 to 9 are wires of the present invention, N
o, 10-20 indicate comparison wires. No. 1-9
0 With the wire of the present invention, no pits were generated, the blowhole generation rate was very low, and a sound weld metal was obtained.

On the other hand, No. 10 has an excessive amount of Si, and N has an excessive amount of Mn.
No. o, No. 15, and No. 20 with an excessive amount of A72 were deoxidized excessively, and pits and blowholes occurred frequently.

Also, No. where the amount of Mn is too small, No. where the amount of If Sin is too small.
, 12, and No. 13 where the amount of l-1-Ti is too small are insufficiently deoxidized, resulting in pits.

Blowholes occur frequently. Furthermore, No. 18 with too little Aff+Ti, No. 19 with too much Aff+Ti, and old,
No. 16 and No. 17, in which the amount of sb is too small, have a high number of pits and a high blowhole occurrence rate. In addition, No. 1.4, which has too little C, has a low 00 partial pressure around the droplet (perhaps because the CO blowout is weak, it is easily affected by zinc, and the number of pits and blowholes are high). It has become.

As described above, it is clear that, for the first time, the present invention makes it possible to obtain a sound welded metal part without pits and with very few blowholes even when welding steel materials that have been subjected to anti-corrosion treatment, such as galvanized steel sheets. be.

Table 2 Steel type and zinc grain size 1'' Figure 1 is a perspective view showing the shape of the test plate used in the example.

Table 3 Welding conditions

Claims (1)

[Claims] (1) C: 0.15-0.30%, Si: 0.
05 to 0.50%, Mn: 0.20 to 1.00%, P: 0.030% or less, S: 0.030% or less, sum of one or two of Al and Ti; 0.020 to
0.200%, total of one or two of Bi and Sb; 0.020~
A gas-shielded arc welding wire characterized in that it contains 0.200% Fe and the remainder consists of Fe and unavoidable impurities.