JPH01197098A - Build-up submerged arc welding method - Google Patents

Abstract

PURPOSE:To obtain the build-up submerged welding excellent in the spread of a bead and having a smooth lap part by welding by using the flux cored wire filling the flux of which component composition is limited in a pipe at the limited wire total weight ratio and the bonding flux for welding in limited bulk density. CONSTITUTION:The filling flux consisting of wt.% 0.8-2.8% C, 4.0-15% Mn, 60-76% Cr, 0.7-12% >=one kind of metal carbonate and an iron powder the balance is filled in the pipe made of 15-30% mild steel at the wire total wt.%. A build-up welding is executed by using this flux cored wire and the bond flux for welding whose bulky density is within the range of 0.75-0.98g/cm<2>. The welding workability optimum for build-up welding, the chemical component of welding metal, hardness and bead spreading, the smoothness of the bead lap part, etc., are obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a 13Cr submerged arc welding method, and more specifically, the present invention relates to a 13Cr submerged arc welding method, and more specifically, the present invention relates to a 13Cr submerged arc welding method, which suppresses the dilution rate to the base metal to a low level, has good bead spread, and has good conformability at the bead overlapped portion. The present invention relates to a build-up submerged arc welding method that provides a bead shape suitable for good roll circumference welding.

[Conventional technology]

BACKGROUND ART Conventionally, various rolls and rollers that are required to have heat resistance and wear resistance in steel works have been refurbished and repaired by overlay welding in order to improve their service life and have been widely put into practical use. However, in recent years, with the trend of dramatic productivity improvement, operating conditions have become even more severe, and strict requirements have been placed on the overlay welding materials and welding methods used to improve performance and productivity. In response to these demands, many methods have become available for overlay welding 13Cr-based weld metals, which can stably obtain high hardness and have excellent heat resistance and corrosion resistance, on the surface of roll rollers.

Conventional 13Cr submerged arc overlay welding methods include a strip electrode welding method using an electrode made of thinly rolled ferritic 13Cr stainless steel that has relatively good workability and processed into a strip shape, a submerged arc welding method also using solid wire, and Flux-cored wires made of mild steel strips containing alloy powder have been put into practical use. However, the submerged arc welding method using these overlay materials has problems in performance and usability. The band electrode welding method, which processes ferritic stainless steel with good workability and uses it as an electrode, is a highly efficient welding method with a low dilution ratio to the base metal and is suitable for overlay welding, but it is suitable for overlay welding, but Since the weld pool becomes large in circumferential welding, the applicable roll size is limited, and application to small diameter rolls (for example, diameter 250 marks φ) is difficult.

In addition, undercuts are likely to occur at the bead overlapped portions, and surface grinding such as rework after welding may require unexpected effort.

Furthermore, in the design of the weld metal components, since ferritic stainless steel with good workability is used, the amount of carbon in the weld metal is determined by using bond flux and replenishing carbon from the flux. The amount becomes unstable, causing segregation, etc. In welding using solid wires, dilution to the base metal is large, and for high-carbon base metals, deterioration of crack resistance must be prevented by underlaying mild steel or increasing the preheating temperature. , it is essential to supplement the welding flux with carbon, which makes the amount of carbon in the weld metal unstable and causes segregation.

On the other hand, welding using a flux-cored wire containing a filling flux consisting of an alloying agent blended with a predetermined composition into a mild steel strip requires less dilution into the base metal, and the alloy composition can be easily adjusted. Although it has the advantage of overlay welding, the manufacturing method of forming and rolling the steel strip allows for seams to span the entire length of the wire. This seam causes the wire to absorb moisture or become twisted, resulting in bits, deterioration in wire feedability, and lack of straight wire stretchability, which can lead to unexpected welding defects such as defects in bead overlaps. .

There is some prior art in the overlay submerged arc welding method, such as "continuous roll overlay welding" described in JP-A-57-89462, but its purpose is continuous roll overlay welding. Regarding metals, it is an overlay weld metal with excellent resistance to weld cracking, curling during use, and wear.The purpose is to improve roll durability, and it is said that this purpose has been achieved with ferritic chrome stainless steel. The technology of the present invention is clearly different from the component design.
- There is a "composite wire for welding" described in Publication No. 180694, but its purpose is a composite wire to obtain wear-resistant weld metal, and it is an austenitic high chromium high manganese composite wire that requires work hardening properties, and the composition is This is clearly different from the present invention in terms of design.

[Problem to be solved by the invention]

The present invention provides wire feedability and moisture absorption resistance comparable to that of solid wire, and low dilution ratio to the base material comparable to that of flux-cored wire in the overlay submerged arc welding method, while at the same time exhibiting excellent bead spread in circumferential welding. It is an object of the present invention to provide a build-up submerged arc welding method that provides good conformability of overlapped parts.

[Failure to solve the problem]

The gist of the present invention is C: O,s~2.8% by weight.

Mn: 4.0-15%, Cr: 60-76%, one or more metal carbonates 0.7-12%, or these and MO:
A flux-cored wire with a bulk density of 0.75-0.0% is a flux-cored wire in which a mild steel pipe is filled with 1.0-3.0% iron powder, the balance being 15-30% of the total weight of the wire.
The present invention relates to an overlay submerged arc welding method characterized by using a welding bond flux in the range of 98 g/ct.

[Function] The present inventors have studied a latent arc welding method for overlaying a martensitic 13% Cr steel weld metal for use in overlaying steel rolls. As a result, as shown in FIG. 1, we obtained knowledge about C and Cri in the weld metal and microcracks on the surface of the weld metal. That is, it has been found that the cracking resistance varies depending on the increase or decrease in the C and Cr contents of the weld metal. The present invention will be explained in detail below.

The filling flux C will be described. In hardfacing welding, C is an essential element for increasing the hardness of the weld metal and improving its wear resistance. However, if C is less than 0.8% based on the total weight of the filling flux, its effect will not be sufficiently exhibited, and it will also cause deterioration of cracking resistance. On the other hand, if it exceeds 2.8%, the weld metal becomes extremely brittle and may cause cracks, so C: 0.
It was defined as 8-2.8%.

Regarding Mn, it has a remarkable deoxidizing effect during welding, and has the effect of preventing weld defects, especially avatars and pits on the bead surface, and at the same time strengthens the matrix of the weld metal, increases hardness, and improves wear resistance. effective. However, if it is less than 4.0% based on the total weight of the filling flux, its effect will not be sufficiently exhibited, causing intergranular cracking and the like. Moreover, if it exceeds 15%, the effect is saturated and minute cracks are observed in the weld metal, which is not preferable.

Cr, like C, increases the hardness of the weld metal and has effects such as corrosion resistance and heat resistance. However, if it is less than 60% of the total weight of the filling flux, the corrosion resistance and cracking resistance of the weld metal will be poor.

Moreover, when it exceeds 76%, the amount of ferrite in the weld metal increases,
Since the cracking resistance is poor, Cr is specified as 60 to 76% based on the total weight of the filling flux.

Regarding metal carbonates, by adding an appropriate amount of one or more carbonates to the flux-cored wire, the stability of the arc was improved, and the welding rate and alloy yield were significantly improved. However, if it is less than 0.7% of the total weight of the filling flux, the effect will not be exhibited, and if it exceeds 12%, the fume will increase due to the generation of carbon dioxide gas, and at the same time, the carbonate added to the wire will reduce the welding speed. teeth,
Since the welding rate tends to decrease slightly if the material is formed only as a slag, the content of one or more carbonates is defined as 0.7 to 12% based on the total weight of the filled flanks. The carbonate mentioned here refers to lime carbonate, barium carbonate, magnesium carbonate, etc.

Next, we will discuss the reason why the mild steel vibrator was filled and the filling rate was specified.

In the case of a conventional flux-cored wire in which flux is wrapped around a mild steel strip, there is a joint between the strips in the longitudinal direction of the wire. This seam causes curling of the wire, which causes a shift in wire feedability and the target welding position, and may result in meandering of the weld bead, making it impossible to obtain a smooth bead overlap. Furthermore, if the wire has been stored for a long time, it is necessary to dry it before welding to remove moisture adhering to the wire surface. In addition, if a wire with rust on the surface or a wire that has absorbed moisture is used as it is, it may cause cracks due to avatars, pits, and hydrogen during welding, and deterioration of slag removability. Therefore, extreme care must be taken when storing and using the wire. It becomes necessary. On the other hand, the wire used in the present invention, in which the pipe is filled with flux, has no seams (openings) on the wire surface, and there are no problems such as curling of the wire or moisture absorption. It is also possible to plate the surface of the wire, which has excellent electrical conductivity, wire rust prevention properties, and feedability, and can be used with solid wires and wires. Another reason for using mild steel pipes is that they are superior mainly in terms of wire drawability.

If you use a vibrator that contains C, Cr, etc.,
There are great benefits in terms of component design and component segregation of weld metal. However, the wire drawability of a vibrator containing hardening elements such as C and Cr is poor, and the pipe itself becomes hard, requiring processes such as multiple annealing and softening of the vibrator, resulting in significantly worse wire drawability than mild steel pipes. . Therefore, it was decided to use a mild steel pipe as the flux-cored wire used in the present invention.

Next, we will discuss the filling rate. What is the filling rate here?1)
Calculated using the formula.

FR = Flux filling rate wp = Pipe weight Wf - Filling flux weight The flux filling rate is greatly affected by the component design of the weld metal and subsequent productivity (especially wire drawability), but in the flux-cored wire used in the present invention, If the flux filling rate is less than 15%, it will be difficult to design the components, and voids will be created inside the vibrator, causing component segregation. Also, if it exceeds 30%,
Wire breaks occur during the wire drawing process during wire manufacturing. In addition, the flux filling rate was specified as 15 to 30% because the target components could be sufficiently obtained with less than 25% in terms of component design.

Regarding Mo, it is well known that Mo is effective in improving creep resistance in the 13 chromium steel of the present invention, and heat resistance is enhanced by adding an appropriate amount of MO. However, if it is less than 1.0% based on the total weight of the filling flux, the effect is not sufficient, and if it exceeds 3.0%, the effect is saturated, so Mo:
It was defined as 1.0 to 3.0%.

The use of the above-mentioned flux-cored wire and the regulation of the bulk density of the welding flux used in combination therewith are important factors in the discovery of the present invention. In other words, in overlay welding in which circumferential welding is performed on rolls and rollers, which is the object of the present invention, the bead width is large and the bead overlapping part is made smooth, which facilitates the rework and grinding process in the finishing process of the weld surface after welding. Not only this, but also the amount of grinding of the excess portion is greatly reduced, resulting in a reduction in welding costs, which is a great advantage.

The present inventors produced a conventional bonded flux in which a flux having the same composition is wet-granulated using water glass, by varying the viscosity of the water glass and the hot granulation time, thereby improving the particle size distribution of the flux. When welding prototype fluxes with varying bulk densities, we found that adjusting the flux particle size and bulk density were highly effective in improving bead width and bead overlap. That is, the bulk density is 0.7
To adjust to less than 5g/cTII, it is necessary to coarsen the particle size of the bond flux, and fine particles of 32 mesh or less need to be cut, so in circumferential welding, flux spills from the roll surface and reaches the exposed arc. Prone. Furthermore, the effect of improving the bead width is saturated and no great expectations can be expected.

Furthermore, when producing flux, a particle size configuration of 8 to 32 meshes significantly reduces the production yield and is not practical. Further, if the bulk density of the flux exceeds 0.98 g/cut, the effect is not sufficient, so the bulk density of the welding bond flux is specified to be in the range of 0.75 to 0.98 g/cl. Note that the bulk density used herein is a value measured according to JISZ 2504 r Apparent Density Testing Method for Metal Powders.

(Example〕 Examples of the present invention will be shown below.

Table 1 shows the pipes used in manufacturing the flux-cored wire. Table 2 shows flux-cored wires made using this pipe. For comparison, flux-cored wires other than those of the present invention were also examined. When welding,
Four layers of circumferential welding were performed on the base metals shown in Table 3, analyzed, and hardness test pieces were prepared and used for testing.

Welding was carried out using the welding flux shown in Table 4. The welding conditions are shown in Table 5. Table 6 shows welding workability and welding performance test results in circumferential welding. The presence of cracks was determined by color checking the surface of the fourth layer weld metal, excluding cracks in the flake portion. The smoothness of the bead overlapped portion was judged to be somewhat poor if the bead overlapped portion was touched with the tip of a fingernail and caught, and was judged to be poor if the overlapped portion was clearly undercut.

In the combination of 5Y-14 and flux F-5 shown in the comparative example, the amount of carbonate added to the filling flux is outside the scope of the present invention,
Furthermore, the bulk density of the welding flux was also outside the scope of the present invention, which caused deterioration in the bead overlap portion and slag removability. Furthermore, the flux filling rate was outside the scope of the present invention, and the weld metal had a low Cr1J and cracking was observed.

In the combination of 5Y-15XF-5 shown in the comparative example, the amount of C in the filling flux exceeds the lower limit of the present invention and the amount of Crl is slightly large, so the balance of C and Cr is poor and ferrite i increases, resulting in microcracks. There has occurred.

In the 5Y-16XF-5 combination shown in the comparative example, the bulk density of the welding flux was outside the scope of the present invention, so the flux spilled out during welding, resulting in a slightly exposed arc, and the slag shape was The peelability was disturbed and the bead overlapped portions were slightly cut. Furthermore, the Mni of the filling flux exceeded the lower limit of the present invention, and fine intergranular cracks occurred on the bead surface.

In the combination of 5Y-17XF-6 shown in the comparative example, the amount of Mn in the filling flux exceeded the upper limit of the present invention, and fine intergranular cracks were observed on the bead surface.

In the combination of 5y-1sXF-1 shown in the comparative example, the flux filling rate exceeded the upper limit of the present invention, and wire breakage occurred during wire drawing, which caused production problems. Moreover, since the amount of Crl in the weld metal increased and the Moi exceeded the upper limit of the present invention, fine cracks were observed on the surface of the weld metal.

In the combination of 5Y-19XF-2 shown in the comparative example, the Crfi in the filling flux exceeded the lower limit of the present invention, and not only the desired 13cr steel weld metal could not be obtained, but also cracking was observed.

In the combination of Comparative Example 5Y-20XF-3, since the amount of carbonate in the filling flux exceeded the upper limit of the present invention, a large amount of fume was generated during welding, and a reduction in the welding rate was observed.

However, wires 5Y-1 to 5Y-13 shown in the example of the present invention
and? In combination with F-1 and 2°3.4 fluxes, the target welding workability, chemical composition of the weld metal, hardness, bead spread, smoothness of the bead overlap, etc. It was found that the obtained product had performance suitable for overlay welding.

〔Effect of the invention〕

As explained in detail above, the present invention uses a flux-cored wire that is filled with a flux made of alloy powder and an appropriate amount of carbonate added to the inside of the vibrator, and controls the bulk density of the welding flux to prevent the bead from spreading. It is now possible to provide a circumferential overlay submerged arc welding method that is good and has smooth overlapping parts.
Its industrial value is great.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between C and Cr1i in the weld metal and the occurrence of cracks in the overlay submerged arc welding method according to the present invention. a 10 /2 /4
16 /8 Q in phosphorus metal, amount 2 (weight ratio)

Claims (2)

[Claims] (1) C: 0.8~2.8%, Mn: 4.0~ by weight
15%, Cr: 60-76%, one or more metal carbonates 0.7-12%, balance iron powder, 15-30% of the total weight of the wire. Flux filled into a mild steel pipe. Wire and bulk density 0.75-0.98g/
An overlay submerged arc welding method characterized by using a welding bond flux in the range of cm^3. (2) C: 0.8~2.8%, Mn: 4.0~ by weight
15%, Cr: 60-76%, Mo: 1.0-3.0%
, 0.7 to 12% of one or more metal carbonates, and 15 to 30% of the total weight of the wire, with the balance consisting of iron powder.
A latent arc welding method characterized by using a flux-cored wire filled in a mild steel pipe and a welding bond flux having a bulk density in the range of 0.75 to 0.98 g/cm^3.