JPS6316239B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a composite wire for welding that has excellent position weldability and mechanical performance of weld metal. [Prior Art] Composite wires for welding in which flux is encapsulated in a steel sheath have been used for some time, but they have a faster welding speed and higher welding efficiency than coated arc welding rods. It also has the advantage that it does not require much skill on the part of the operator. On the other hand, compared to solid wire, it is possible to add arc stabilizers and slag agents, so the arc is stabilized even with CO ₂ shielding solution.
Welding with less spatter is possible, and the bead is completely covered with the generated slag, giving it a beautiful appearance. Composite wires having such characteristics are beginning to be widely used in various industrial fields such as shipbuilding, machinery building, bridges, architecture, and pressure vessels. Especially among composite wires
Small diameter wires with a diameter of 1.2 to 1.6 mm and mainly composed of TiO ₂ have become the majority of wires because they are said to be easy to operate and have high welding efficiency. [Problems to be solved by the present invention] Small-diameter composite wires mainly composed of TiO ₂ are widely used because they are said to have good operability, welding workability, and welding efficiency. There is a strong desire from industry to do this. However, when welding a composite wire mainly composed of TiO ₂ , such as the composite wire described in JP-A No. 56-128699, when welding at a higher current, the bead melts down during upward welding or upward welding. There is a problem that welding cannot be continued. [Object of the present invention and means for solving the problem] Therefore, the object of the present invention is to obtain a high-efficiency wire that can be welded in a position with a high current, and its gist is to obtain a wire that does not contain Nb or V as impurities. And welding flux containing 25 to 50% by weight of Ti oxide shown by the formula below, and other components such as ordinary slag agents, arc stabilizers, alloying agents, deoxidizers, etc., is added to the total weight of the wire at 8% This is a welding composite wire characterized by ~25% filling. 0.2≦lower Ti oxide/total Ti oxide≦0.8 The present invention will be described in detail below. The present inventors vertically welded a 60 degree V-groove groove with a 1.2 mmφ composite wire mainly composed of _TiO2 , and the bead was almost smooth up to 180 A, but at 200 A.
With 210A, the bead was a little droopy, and with 210A it was found that the metal melted off. Observing the process until it melts down, we can see that as the current increases, the arc force becomes stronger, the digging effect of the arc becomes stronger, the molten metal is pushed forward, the bead starts to droop, and finally it melts down. Ivy. Therefore, in order to increase the current and perform postural welding with high efficiency, it is necessary to weaken the digging action of the arc or to increase the fire resistance of the slag to strengthen the slag's ability to hold the metal. Although the use of alkali metals such as Li, Na, and K is an effective method for stabilizing the arc and reducing the penetration of molten metal,
It is well known that TiO ₂ , which is used in large quantities, also has an arc stabilizing effect. Therefore, the present inventors investigated Ti oxides other than TiO ₂ as raw materials for composite wires, and found that
It was discovered that lower Ti oxides such as Ti ₂ O ₃ and Ti ₃ O ₅ weaken the digging-down effect of the arc. It was also found that because the solidification temperature is higher than that of TiO ₂ , the solidification time is earlier, the bead retention effect during positional welding is greater, and positional weldability is significantly improved. It is necessary that lower Ti oxides having such characteristics be contained in a proportion of 20% or more of the Ti oxides. 20
If it is less than %, the above effects will not be sufficiently exhibited. Although there is no problem in terms of welding workability even if the entire amount of Ti oxide is replaced with lower Ti oxide, it has become clear that there is another problem. That is, it has been found that a large amount of Nb and V contained as impurities in Ti oxide remain in the weld metal, leading to deterioration of the notch toughness of the weld metal. In particular, toughness deterioration after SR is severe. The reason for this is presumed to be that the lower Ti oxide acts as a deoxidizing agent and thus increases the yield of Nb and V in the slag-metal reaction during welding. According to experiments conducted by the present inventors, as shown in Figure 1, the yield of Nb+V does not change much until the proportion of lower oxides in the Ti oxide reaches 80%, and the notch toughness of the weld metal remains at a high value. However, if it is added in excess of 80%, Nb+
The yield of V increases and the notch toughness begins to decrease. Therefore, the upper limit of the addition ratio of the lower Ti oxide must be 80%. In the present invention, these Ti oxides are used as the main component of the filling flux at least 25% or more, preferably 30% or more.
% or more to stabilize the arc. Furthermore, if too large a quantity is added, slag entrainment may occur or other flux components may become insufficient, so the upper limit of addition is set at 50%. The finer the particle size of the added Ti oxide, the greater the arc stabilizing effect, especially if the particle size is less than 100 mesh.
It is desirable to set it to 50% or more. This is because CO ₂ welding uses wire-positive polarity, so the surface of the molten pool, which serves as a cathode, is uniformly covered with fine Ti oxide particles with high electron-emitting ability, which stabilizes arc generation from the molten pool. Seem. As other fluxes, commonly used slag agents, arc stabilizers, alloying agents, deoxidizing agents, etc. can be added using conventional methods. In particular, by adding 0.5% or more of Li, Na, K, etc. in the form of fluorides, carbonates, oxides, etc. as arc stabilizers, an extremely stable arc can be created, which only improves posture weldability. This makes it possible to significantly reduce spatter in welding in any position. In the present invention, these fluxes are filled in an amount of 8 to 25% based on the total weight of the wire. If it is less than 8%, sufficient action and effect cannot be expected due to insufficient flux, and if it exceeds 25%, the risk of wire breakage occurring during wire production increases. Therefore, in the wire of the present invention, the flux filling ratio is in the range of 8 to 25%. Furthermore, in the wire of the present invention, B is added to the filling flux.
By adding 0.01 to 0.15% of Ti, it is possible to improve the toughness of the weld metal through a synergistic effect with lower Ti oxides. In addition, the total amount of these fluxes was converted into water glass, carboxymethyl cellulose (hereinafter referred to as CMC).
It can be granulated and filled by any suitable method. Particularly when adding a large amount of fine Ti oxide, granulation prior to filling is extremely effective in improving filling properties and at the same time preventing segregation. Next, the effects of the present invention obtained through the above experimental investigation were confirmed through Examples. [Example] Table 1 shows the configuration of the prototype wire, and Table 2 shows the test results. In Table 1, wires Nos. 1 and 2 are comparative examples, and Nos. 3 to 8 are examples of wires according to the present invention. All wires use a mild steel outer sheath, and in the case of open seam wires, after filling with flux, forming and
The wire was drawn to a diameter of 1.2 mm and fired at 350°C. The wire surface was coated with graphite and molybdenum disulfide to improve feedability during welding. In the case of closed seam wire, a pre-prepared 11mmφ electric resistance welded steel pipe is filled with flux and the pipe while vibrating using the technique described in Japanese Patent Publication No. 45-30937, and annealed at 650℃ in the middle of wire drawing. ,
The surface of the wire was plated with Cu and finished to 1.2mmφ. In addition, wire No. 5 to 7 is 0.02% [C] -0.02
% [O] low carbon skin was used. First, the positional weldability of each wire was examined by vertical advancement welding on a 60° V-groove steel plate, and the welding limit current value was determined and compared. As a result, wire No. 1, whose Ti oxide is only TiO ₂ , has a limiting current of 200 A, whereas wire No. 2 to No. 8, which contains 20% or more of lower Ti oxide, has a limiting current of 200 A.
This wire was capable of vertical advancement welding even at 230 to 260A. On the other hand, the toughness of the welded metal is 300A, and the heat input is 20kJ/cm.
After creating weld metal and performing SR at 625℃ for 1 hour,
An impact test was conducted to determine the fracture surface transition temperature. No.2 where the proportion of lower Ti oxide in Ti oxide is 100%
The wire has Nb+V of 0.032% and vTrs is -8
It becomes brittle at ℃. On the other hand, wires No. 1 and 3 to 8 exhibited good notch toughness with vTrs of -30°C or less. Therefore, it was found that wires Nos. 3 to 8 according to the present invention were excellent in both position weldability and mechanical performance of the weld metal.

【table】

[Table] * Comparative example

[Table] * Comparative example

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the ratio of lower Ti oxide/total Ti oxide, Nb+V in the weld metal, and the fracture surface transition temperature after SR.

Claims (1)

[Scope of Claims] 1 Contains Nb and V as impurities and contains Ti oxide represented by the following formula in a weight ratio of 25 to 50%, and the rest are ordinary slag agents, arc stabilizers, alloying agents, and deoxidizing agents. A composite wire for welding, characterized in that it is filled with a welding flux consisting of 8 to 25% of the total weight of the wire. 0.2≦lower Ti oxide/total Ti oxide≦0.8