JPS6163397A - Composite wire for co2 gas arc welding for hardening built-up welding - Google Patents

Abstract

PURPOSE:To improve crack resistance and peeling properties of slag by forming a composite wire by packing a soft steel-made skin with a flux containing TiO2, MgO, ZrO2, Cr, etc. of specified wt%, by a prescribed weight ratio. CONSTITUTION:A flux is composed of 3-20% TiO2, 5-15% ion oxide, 1-10% SiO2, 5-20% ZrO2, 1-5% metallic fluoride, 5-15% MgO, 5-15% Mn, 2-40% Cr, 1-10% Si, and 2-5% C. Also, a soft iron-made skin is packed with the flux by a ratio packing rate of 5-30% by a weight ratio. The crack resistance of a built-up welding metal and the peeling properties of slag are improved by a correct mixed quantity of components such as TiO2, MgO, ZrO2, etc. in the flux.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a hardfacing weld metal that can obtain welding efficiency comparable to that of solid wire and has good cracking resistance and welding workability. The present invention relates to a composite wire for CO2 gas arc welding.

[Conventional technology]

Hardfacing welding has become popular as a means of repairing wear and tear on various parts of iron and steel manufacturing equipment, civil engineering and construction machinery, etc. This hardfacing welding was previously performed by hand welding using a coated arc welding rod, but recently it has become possible to perform fully automatic or semi-automatic gas metal arc welding (hereinafter referred to as G-metal arc welding).
(referred to as MA) has become mainstream. By the way, solid wire is the most common material for GMA welding.
If fully automatic or semi-automatic GMA welding using this wire is employed, welding efficiency 3 to 4 times that of manual welding can be obtained. However, GMA welding using solid wire has the problem of poor slag envelopment and poor slag removability.As a result, there are areas where 8 weld beads overlap, and new build-up is required on top of the previous bead. The arc tends to become unstable in the area where the welding occurs, and a light layer forms at 8m of the center where slag entrainment occurs, making it impossible to obtain a sound hardfacing welded gold coin.

As a welding material that does not cause such problems, a composite wire for hardfacing CO□ gas arc welding has been proposed, for example, as disclosed in JP-A-56-122699. This composite wire is made by filling the inner cavity of the soft myopia with a flux of a specific composition, and it has good slag envelopment properties, improves the smoothness of the bead overlap area, and also has good slag removal properties. However, it is disclosed that welding efficiency comparable to that of solid wire can be obtained.

[Problem that the invention seeks to solve]

By using the composite wire disclosed in the above-mentioned publication, it is possible to obtain welding efficiency that is much higher than that obtained when using a solid wire, and it is also possible to improve the smoothness of the peat overlap part disclosed in the publication 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 main purpose of materials for hardfacing welding is to increase hardness, cracking resistance tends to be insufficiently considered. When a crack occurs, 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.

In addition, overlay welding inevitably creates an overlapping area between beads, but if slag removability is poor and slag remains in the overlapping area, 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 removability of the overlay weld metal, resulting in poor welding workability. (Also, there remains a problem with the reliability of overlay weld metal.

[Means for solving problems]

The present inventors have focused on the above-mentioned circumstances, and in order to improve the cracking resistance and slag removability of hot overlay weld metal while maintaining the features of composite wire, we have developed a method using mainly filler flux components. I've been doing a lot of research. The present invention was completed as a result of such research, and its configuration is such that a flux having the following composition is applied to the inner cavity of a mild steel outer shell at a weight ratio of 5 to the outer shell (hereinafter simply referred to as flux filling rate).
The gist of this is that it is filled to a level of ~30%.

(Flux composition) T102: 3 to 20% (weight %: the same below) Iron oxide: 5 to 15% SiO: 1 to 10% ZrO: 5 to 20% Metal fluoride = 1 to 5% Mg0: 5 to 15 % Mn: 5 to 15% Cr: 2 to 40% Si: 1 to 10% C: 0.2 to 5% [Function] The present inventors solved the aforementioned problems pointed out in the conventional composite wire for CO2 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, we reduced the amount of TiO□ in the filling flux, added an appropriate amount of MgO, and added iron oxide and Zr.
It has been found that by increasing the blending amount of O2, a composite wire can be obtained that provides a hardfacing weld metal with good welding workability, particularly good slag removability, and excellent cracking resistance.

Incidentally, Figure 1 shows composite wires obtained by using the flux composition shown in Table 1 as the basic composition and varying the amounts of MgO and TiO□ (sheath: 5PCC material, flux filling rate: 18%, wire diameter: 1.2Bφ) is a graph showing the cracking resistance of overlay weld metal. However, in the cracking resistance test, as shown in Fig. 2, after restraint welding the base metal 2 to the upper surface of the restraint plate 1, overlay welding 3 (three-way welding) is performed using each composite wire, and the surface is color checked. The presence or absence of cracks was observed.

(Actual conditions) Wire diameter: 1.2 diameter Welding current: 270A Welding voltage: 32V Welding speed: 35crn/min Preheating ◆ Interpass temperature: 150-200℃ Base material: Soft gate bond PJ: A calendar color Check criteria: O...No cracks △...Cracks occur in 1 to 10 locations ×...Cracks occur in 10 or more locations'/'0-' Table 1 Basic flux composition (weight n% ) 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 the overlay weld metal can be improved. can.

Next, Figure 3 shows composite wires prepared using the Franks component shown in Table 2 as the basic composition, and varying the amount of ZrO2' and iron oxide in different countries (sheath: 5 pcc material, flux filling rate: 18%, wire It is a graph showing the slag removability when using a diameter of 1.2InIφ). However, in the slag peeling test, the thickness was 12 mm and the width was 75 mm, as shown in Figure 3.
Overlay welding was performed on the surface of the base material 2 so that two weld beads 3 overlapped each other at the sides, and the slag removability after welding was examined.

(Mounting conditions) Wire diameter: 1.2#φ Welding current: 270A (DC-RP) Welding voltage = 32v Welding speed: 85cnt/min Preheating 0 pass temperature = 15o~2oooC Base material: Annealed copper (SPCC) Slag stripping Female determination: ○: Good, △: Slightly bad, ×: Poor As is clear from Figure 8, 5% or more of Zr was present in the filling flux.
Slag removability can be improved by blending O□ with 5% or more of iron oxide. As mentioned above, the most characteristic structure of the present invention is the combination of TiO□, Mg0Szro2 and iron oxide in the filling flux. Although the compounding ratio of these materials is strictly determined from the viewpoint of "improving cracking resistance and slag removability," arc It is necessary to decide the blending ratio of the above components and other components after comprehensively considering stability, slag encapsulability, smoothness of the bead overlap part, etc. The reason for setting the component composition is as follows.

TiO□: 3 to 20% Increases arc stability and improves slag encapsulation (thus reducing bead bulges, reducing the rising angle of the bead toe and increasing the smoothness of the bead overlap area) In order to effectively exert this effect, the content must be 3% or more. However, if the content exceeds 20%, the cracking resistance of the weld metal overlay on the ladder described in Figure 1 will decrease.
The effects unique to the present invention cannot be obtained.

Iron oxide: 5 to 15% As shown in Figure 1, it is an essential component for improving slag removability, and if it is less than 5%, the effect will not be exhibited.

However, if the amount is too large, the fluidity of the slag becomes too high, the slag envelopment property deteriorates, and the bead shape becomes poor.

5in2: 1 to 10% In order to maintain good arc stability, the content must be 1% or more, but on the other hand, if it is too large, the number of spatter-generating claws will increase abnormally, so it must be kept below 10%.

ZrO2: 5-20' As shown in FIG. 3, when 5-15% iron oxide and 5% or more ZrO2 are used together, the slag removability can be significantly improved. However, if it exceeds 20%, the fluidity of the slag becomes excessive, the slag envelopment property deteriorates, and a good bead shape cannot be obtained.

Metal fluoride = 1 to 5% It has the function of increasing arc stability, and if it is less than 1%, the function is not effectively exhibited. However, if it exceeds 5%, the viscosity of the slag decreases and the bead appearance deteriorates.

λ Castle 0: 5 to 15% As explained in Figure 1, there is a mutual effect of suppressing TiO2 to 20% or less, which has the effect of significantly increasing cracking resistance, and if it is less than 5%, this effect is not sufficient. Not demonstrated. However, if the amount is too large, the fluidity of the slag becomes too high, the slag envelopment property deteriorates, and the bead shape deteriorates.

Mn: 5-15% Mn is an essential component to function as a deoxidizing agent and improve the cleanliness of overlay weld metal, and if it is less than 5%, its effect will not be effectively exhibited. However, if it is too large, the slag tends to seize and the releasability decreases, so it must be kept below 15%.

Cr: 2-40% This is an essential component to ensure the original hardness of the hardfacing weld metal, and if it is less than 2%, it is impossible to obtain the desired hardness. However, if it exceeds 40%, it becomes too hard and susceptible to cracking.

Si: 1-10% It is a strong deoxidizing component, and must be contained in an amount of 1% or more in order to obtain a clean overlay weld metal.

However, if the amount is too high, the viscosity of the slag becomes excessive and the appearance of the bead deteriorates.

C: 0.2 to 5% In order to give a predetermined hardness to the overlay weld metal, it must be contained in an amount of 0.2% or more. However, if it is too large, the weld metal becomes too hard and becomes more susceptible to cracking, so it must be kept below 5%.

Although the filling flux used in the present invention essentially contains the above-mentioned components, it may also contain other components of iron powder 4 within a range that does not adversely affect the above-mentioned range of components.

The composite wire of the present invention is made by filling mild steel lumber with flux having the above-mentioned composition.
■ A method of filling a mild steel pipe with the powdered flux and then drawing it to a predetermined cross-sectional dimension. ■ Filling the inside of a mild steel belt with powdery flux while bending it into a pipe shape, and then In the method of drawing wire to a predetermined cross-sectional dimension, or in the method described in ■ above, the abutting parts of both side edges of the steel strip curved into a pipe shape are seam welded by resistance welding, TIG welding, etc., and the gap between the joints is welded. How to eliminate
However, in this case, the flux filling rate is soft #l! It must be set within a range of 5 to 30% of the weight of the J outer skin. However, if the filling rate is less than 5%, no matter how properly the flux composition is adjusted, the absolute amount of flux will tend to be insufficient, and it will not be possible to maintain good welding workability including arc stability. The physical properties of the welded metal, especially the hardness, tend to be insufficient. On the other hand, if the filling rate exceeds 30%, too much slag n will be produced, resulting in deterioration of the bead appearance or problems such as slag entrainment.

〔Example〕

Using a powder flux with the chemical composition shown in Table 4 and a mild steel shell material with the chemical composition shown in Table 3, the outer diameter was 1.2 Bφ.
A composite wire was fabricated. However, the flux filling rate is 4th
It was as shown in the table.

Table 3 Chemical composition of outer skin material (wt%) Using each composite wire obtained, the following methods were used to determine arc stability, spatter occurrence, slag removability, bead appearance, and sealing property of overlay weld metal. I looked into it.

Slag stripping property: Performed according to the method shown in Figure 3.

Arc stability: The number of arc breaks and the amplitude of the arc voltage were observed.

Outside the bead i: Bead wavy pattern, stability of bead width, conformability, etc. were observed.

Spatter: The state of spatter scattering during welding was observed.

Confinement property 2. Measured according to the method shown in Figure 1.

The results are summarized in Table 5.

Table 5 O: Good, Δ: Slightly poor, ×: Poor From Table 4.5, the following can be considered.

No. 10-16 is an example that satisfies all the specified requirements of the present invention, and has good arc stability, little spatter, good slag removability, and excellent bead appearance, as well as hardfacing weld metal. The confinement of the layer is also much better. On the other hand, composite wires No. 1 to 9 are comparative examples that lack at least one of the specified requirements, and have some performance problems as described below.

NQ, 1: Bead appearance is poor due to lack of Ti02Q.

No. 2: Too much TiO2m, resulting in poor closing performance.

No. 3: Poor slag peeling properties due to lack of iron oxide n, and excessive spatter occurrence due to too large amount of SiO2.

No. 71: The bead appearance is poor because the amount of iron oxide is too large, the arc is unstable due to insufficient gold shoulder fluoride calm, and the closing property is poor because 5 ift is too large.

No. 5: The arc is unstable due to insufficient SiO□ gas, and the bead appearance is poor due to too much gold monofluoride.

No. 6: Slag removability is poor due to insufficient ZrO□ amount, and blowhole defects are observed due to insufficient Mnfi, resulting in insufficient deoxidation.

No. 7: The slag removability is poor because there is too much MnJi, and the bead appearance is not good because the amount of ZrO2 is too large.

No. 8: (Because of the lack of Goffi, #1 crackability could not be improved, and due to the lack of Cr and Cfi, sufficient hardness could not be given to the overlay weld metal.

No. 9: The closing property is poor because the amount of Cr and the amount of C are too large, and the bead shape is also bad because the amount of Mg0R is too large. Moreover, since the amount of Si was less than the specified amount, blowhole defects due to insufficient deoxidation were observed.

〔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 original characteristics of the composite wire for hardfacing welding can be maintained while the problems pointed out have been addressed. It was possible to significantly improve the slag removability and cracking resistance. As a result, it has become possible to form a hardfacing weld metal with very high performance and good workability with a high level of welding mark rate comparable to that of solid wire.

[Brief explanation of drawings]

Figure 1 is a graph of experimental results showing the influence of Mg011 and TiO2M in Franx on the cracking resistance of hardfacing weld metal, Figure 2 is an explanatory diagram showing the overlay welding method adopted in the cracking resistance test, Figure 3 is a graph of actual results showing the influence of the amount of iron oxide in Franks and ZrO□ flying on slag removability, and Figure 4 is an explanatory diagram showing the overlay welding method adopted in the slag removability confirmation experiment. . 1. Restriction plate, 2. Base material, 3. Overlay weld bead.

Claims (1)

[Scope of Claims] A flux 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 CO_2 gas arc welding. (Flux composition) TiO_2: 3 to 20% (weight%: the same below) Iron oxide: 5 to 15% SiO_2: 1 to 10% ZrO_2: 5 to 20% Metal fluoride: 1 to 5% MgO: 5 to 15 % Mn: 5-15% Cr: 2-40% Si: 1-10% C: 0.2-5%