JPH032597B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is a CO ₂ hardfacing weld metal that can obtain welding efficiency comparable to that of solid wire and also has good cracking resistance and welding workability.
This invention relates to a composite wire for gas arc welding. [Prior Art] Hardfacing welding has become popular as a means of repairing wear of various parts of iron and steel manufacturing equipment, civil engineering and construction machinery, etc. This hardfacing welding was previously carried out by hand welding using a coated arc welding rod, but recently it has become fully automatic or semi-automatic gas metal arc welding (hereinafter referred to as GMA).
has become the mainstream. By the way, solid wire is the most common material for GMA welding.
Fully automatic or semi-automatic GMA using this wire
By employing welding, it is possible to obtain welding efficiency 3 to 4 times that of manual welding. However, GMA welding using solid wire has the problem of poor slag envelopment and poor slag peelability.As a result, there are areas where adjacent welding bead overlap, or where new welding is performed on top of the previous bead. The arc tends to become unstable in the part where the weld metal goes, which eventually leads to problems such as slag entrainment, making it impossible to obtain a sound hardfacing weld metal. As a welding material that does not cause such problems, a composite wire for CO ₂ gas arc welding for hardfacing has been proposed, for example, as disclosed in JP-A-56-122699. This composite wire is made by filling the inner cavity of a mild steel outer shell with a flux of a specific composition, which has good slag envelopment properties, improves the smoothness of the bead overlap area, and also has good slag removal properties. can be,
Moreover, it is disclosed that welding efficiency comparable to that of solid wire can be obtained. [Problems to be Solved by the Invention] If the composite wire disclosed in the above publication is used, it is possible to obtain welding efficiency comparable to that when using a solid wire, and as disclosed in the publication, the welding efficiency of the bead overlapped portion can be improved. It is possible to improve the smoothness to some extent. However, the cracking resistance and welding workability of overlay weld metal are still insufficient. Furthermore, it cannot be said that the slag releasability has been sufficiently improved. In other words, since the primary purpose of hardfacing welding materials is to increase hardness, cracking resistance tends to be insufficiently considered.
If a crack (hot crack or cold crack) occurs in the overlay weld, wear progresses selectively from that part, and the crack progresses due to the stress (external force and internal stress) received during use, causing breakage accidents, etc. . In addition, overlay welding inevitably creates an overlap between beads, but if slag removability is poor and slag remains in the overlap, the bead shape in this area will deteriorate and slag entrainment defects will appear. This necessitates re-welding and significantly reduces welding workability, but the composite wire disclosed in the above-mentioned publication has problems with the cracking resistance and slag removal of the overlay weld metal, resulting in poor welding workability. In addition, there remains a problem in the reliability of overlay weld metal. [Means for solving the problem] The present inventors focused on the above-mentioned circumstances, and aimed to improve the cracking resistance and slag removability of overlay weld metal while maintaining the features of composite wire. We have been conducting various research, especially focusing on filling flux components. The present invention has been completed as a result of such research, and has a structure in which a flux having the following composition is applied to the inner cavity of a mild steel outer shell at a weight ratio (hereinafter simply referred to as flux filling rate) to the outer shell of 5 to 5. The gist of this is that it is filled to a level of 30%. (Flux composition) TiO ₂ : 3-20% (weight %: same below) Iron oxide: 5-15% SiO ₂ : 1-10% ZrO ₂ : 5-20% Metal fluoride: 1-5% MgO: 5 to 15% Mn: 5 to 15% Cr: 2 to 40% Si: 1 to 10% C: 0.2 to 5% [Function] The present inventors have solved the above-mentioned problems pointed out in the conventional composite wire for CO ₂ gas arc welding. In order to solve this problem, various experiments have been carried out starting from a review of the filling flux composition. As a result, if the amount of TiO ₂ in the filling flux is reduced, an appropriate amount of MgO is added, and the amounts of iron oxide and ZrO ₂ are increased, welding workability, especially slag peelability, can be improved and the welding resistance can be improved. It has been found that a composite wire can be obtained that provides a hardfacing weld metal with excellent crackability. Incidentally, Figure 1 shows composite wires obtained by using the flux components shown in Table 1 as the basic composition and varying the amounts of MgO and TiO ₂ (sheath: SPCC material, flux filling rate: 18%, wire diameter: 1.2mm〓) is a graph showing the cracking resistance of overlay weld metal. However, in the cracking resistance test, after restraint welding the base metal 2 to the upper surface of the restraint plate 1 as shown in Fig. 2, overlay welding 3 (three-layer welding) using each composite wire was performed.
The surface was color checked to observe the presence or absence of cracks. (Experimental conditions) Wire diameter: 1.2mm Welding current: 270A Welding voltage: 32V Welding speed: 35cm/min Preheating/interpass temperature: 150-200℃ Base material: Mild steel Lamination: 3-layer color check criteria: ○… No cracks △…Cracks occur in 1 to 10 locations ×…Cracks occur in 10 or more locations

【table】

[Table] As is clear from Figure 1, if 5% or more of MgO is added to the filling flux and the amount of _TiO2 is kept to 20% or less, the cracking resistance of overlay weld metal can be improved. be able to. Next, Figure 3 shows composite wires prepared with the basic composition of the flux components shown in Table 2 and varying amounts of ZrO ₂ and iron oxide (exterior shell: SPCC material,
This is a graph showing the slag removability when using flux filling rate: 18%, wire diameter: 1.2 mm. However, in the slag peeling test, two weld beads 3 are overlaid on the surface of the base metal 2 with a thickness of 12 mm and a width of 75 mm, overlapping each other at the sides, as shown in Figure 3, and the slag peeling is performed after welding. I looked into gender. (Experiment conditions) Wire diameter: 1.2mm Welding current: 270A (DC/RP) Welding voltage: 32V Welding speed: 35cm/min Preheating/interpass temperature: 150 to 200℃ Base material: Mild steel (SPCC) Slag removability judgment : ○...Good, △...Slightly bad, ×...Poor

〔Example〕

Powder-like flux having the component composition shown in Table 4,
Using a mild steel shell material with the chemical composition shown in Table 3,
A composite wire with an outer diameter of 1.2 mm was fabricated. However, the flux filling rate was as shown in Table 4.

【table】

【table】

【table】

[Table] Using each of the obtained composite wires, arc stability, spatter occurrence, slag removability, bead appearance, and crack resistance of overlay weld metal were investigated using the following methods. Slag removability: Performed according to the method shown in FIG. Arc stability: The number of arc breaks and the amplitude of the arc voltage were observed. Bead appearance: bead wavy pattern, stability of bead width,
We observed familiarity, etc. Spatter: The state of spatter being scattered during welding was observed. Cracking resistance: Measured according to the method shown in FIG. The results are summarized in Table 5.

〔Effect of the invention〕

The present invention is constructed as described above, but the key point is that by strictly specifying the composition of the filling flux, the inherent characteristics of the composite wire required for hardfacing welding can be maintained, while the problems pointed out can be solved. It was possible to significantly improve the slag removability and cracking resistance. As a result, it has become possible to form high-performance hardfacing weld metal with good workability at a high level of welding efficiency comparable to that of solid wire.

[Brief explanation of the drawing]

Figure 1 is a graph of experimental results showing the influence of the amount of MgO and _TiO2 in flux on the cracking resistance of hardfacing weld metal, and Figure 2 shows the overlay welding method used in the cracking resistance test. An explanatory diagram, Figure 3, shows the effect of the amount of iron oxide in flux on slag removability and
A graph of the experimental results showing the influence of the amount of ZrO ₂ , and FIG. 4 is an explanatory diagram showing the overlay welding method used in the experiment to confirm slag removability. 1... Restriction plate, 2... Base metal, 3... Overlay weld bead.

Claims (1)

[Scope of Claims] 1. For hardfacing welding, characterized in that the inner cavity of a mild steel outer skin is filled with a flux having the following composition so that the weight ratio to the outer skin is 5 to 30%. Composite wire for _CO2 gas arc welding. (Flux composition) TiO ₂ : 3-20% (weight %: same below) Iron oxide: 5-15% SiO ₂ : 1-10% ZrO ₂ : 5-20% Metal fluoride: 1-5% MgO: 5-15% Mn: 5-15% Cr: 2-40% Si: 1-10% C: 0.2-5%