JPH06114591A - Flux for build-up welding - Google Patents

Abstract

PURPOSE:To provide a build-up welding material with which a weld metal having excellent heat flux resistance, wear resistance, etc., is obtainable by specifying the chemical compsn. of the flux and using this flux in combination with a specific wire. CONSTITUTION:This flux has the compsn. contg. 2.5-8.0% CO2, 5-15% CaO, 15-30% SiO2, 10-30% ZrO2, 2-10% metal fluoride and 10-30% MgO and satisfying Al2O3>=5% and 10%<=-4XAl2O3,(%)+MgO(%)<=40 and is further so adjusted as to contain C, Ni, Mo and one or >=2 kinds among V, Nb and W within determined ranges. The flux is used in combination with the 13Cr wire. As a result, the procedure meeting build-up welding of a small-diameter roll is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux for overlay welding, and is particularly suitable for overlay welding of rolls which are used under high temperature and which are required to have good corrosion resistance, heat crack resistance and wear resistance. It relates to welding flux.

[0002]

BACKGROUND OF THE INVENTION Like a continuous casting roll or a transfer roll of a hot rolling line, it repeatedly comes into contact with a high temperature metal piece and is heated by heat transfer from the metal piece or by water or steam. The roll that is cooled needs heat crack resistance, corrosion resistance, and wear resistance that can withstand the use environment.

Conventionally, martensitic stainless steel composed of a basic component system containing 1 to 6% of Ni in 13Cr has been widely used as a cladding material for imparting these characteristics. However, in these rolls,
There has been a problem that cracks are generated on the roll surface early in use due to thermal stress generated by repeated heating and cooling, and the life of the roll is significantly reduced. Further, in a roll such as a pinch roll or a split type roll used in a continuous casting machine, wear due to contact with a slab is likely to cause roll replacement, the roll by improving wear resistance of the overlay metal The expectation for a longer service life was high.

In order to solve such a problem, the present inventors have previously proposed a build-up welding material having excellent heat crack resistance, wear resistance and corrosion resistance (Japanese Patent Laid-Open No. 3-498).
issue). However, when applying the overlay welding material to rolls of various shapes thereafter, when submerged arc welding is performed on rolls with small diameters or roll journals, the temperature of the overlay increases and the slag peels off. Was significantly deteriorated and slag was also markedly burned, which made it difficult to perform continuous welding such as spiral welding. Therefore, there has been a demand for a flux for submerged arc welding which has good workability and is excellent in wear resistance, heat crack resistance and corrosion resistance.

The present invention has been made in order to meet such demands, and it is possible to obtain a weld metal having excellent heat crack resistance, wear resistance and corrosion resistance, and at the same time, to perform overlay welding with good workability. The purpose is to provide the material.

[0006]

When a small-diameter roll is continuously welded, it is inevitable that the roll temperature rises to some extent. Therefore, a flux having good workability even at a relatively high interpass temperature is required.

In view of the above points, the inventors of the present invention have made earnest studies, and as a result, by defining a specific component in the build-up welding flux used in combination with the wire of 13Cr or 17Cr steel, the performance is improved. It was found that not only the flux with good workability can be provided, but the present invention has been completed here.

That is, according to the present invention, CO ₂ : 2.5 to 8.
0%, CaO: 5~15%, SiO 2: 15~30%, Zr
O _2: 10~30%, metal fluoride: 2~10%, Mg
O: 10 to 30%, Al ₂ O ₃ ≤ 5%, and a composition satisfying the following formula: 10% ≤ 4 x Al ₂ O ₃ (%) + MgO (%) ≤ 40%. , [M] D = af × [M] f + aw × [M] w (1) where [M] D: content (%) of alloy component M in the weld metal [M] f: flux Content of alloy component M in alloy (%) [M] w: Content of alloy component M in wire (%) af: Yield coefficient from flux of alloy component M to weld metal aw: From wire of alloy component M Yield coefficient to weld metal In the alloy component amount (calculated value) of the weld metal represented by the above formula (1), [C] D: 0.1 to 0.4% [Ni] D: 0.5 to 3. 5% [Mo] D: contains C, Ni and Mo satisfying the range of 0.5 to 2.5%, and [V] D, [Nb] D and [W] obtained from the above formula (1). ] D, the following equation 0.01% ≦ (1/4) × [V] D + (1/8) × [Nb] D + (1/15) ×
It contains one or more of V, Nb and W satisfying [W] D ≦ 0.6% and, if necessary, further calculated from the above formula (1) [C
Regarding u] D, the meat used in combination with 13Cr-based or 17Cr-based flux-cored wire or solid wire, characterized in that [Cu] D is adjusted to contain Cu satisfying 0.2-2% The main focus is on welding flux.

[0009]

[Action]

First, the reasons for defining each component in the present invention will be described.

[0011]CO _2: 2.5~8.0%  CO₂Has the effect of maintaining the shielding property against the atmosphere.
For this, 2.5% or more is required, but 8.0%
If it exceeds, turbulence in the molten pool will occur easily, and slag entrapment will occur.
It is easy to cause adverse effects such as deterioration of the bead and familiarity with the bead. Na
Oh, CO₂Is heated to CO₂If it is a material that generates
For example, calcium carbonate, barium carbonate, carbonated carbonate
Examples include Rontium and manganese carbonate.

CaO: 5 to 15% CaO has the effect of increasing the viscosity of the flux, but in order to effectively obtain this effect, it must be contained in an amount of 5% or more. However, if it exceeds 15%, frequent occurrence of pockmarks may occur.

SiO ₂ : 15 to 30% SiO ₂ improves the peelability of the slag and smoothes the bead shape to improve the conformability, but if it is less than 15%, its effect is not effectively exhibited. On the other hand, if it exceeds 30%, the risk of hot cracking increases, and the melting point of the slag decreases, deteriorating the bead shape during roll buildup.

ZrO ₂ : 10 to 30% ZrO ₂ contributes to arc stability and exhibits an effect of improving the bead shape, but if it is less than 10%, the effect is not sufficiently obtained, while on the other hand, it exceeds 30%. And the peelability of the slag deteriorates and the bead shape becomes poor.

Metal Fluoride: 2 to 10% Metal Fluoride is effective in improving arc stability and smoothing the bead shape, but if it is less than 2%, a sufficient effect cannot be obtained. If it exceeds%, undercutting tends to occur. Although various kinds of metal fluorides are possible, fluorite and cryolite are typical ones, and barium fluoride and the like are also applicable.

[0016]MgO: 10-30%, Al ₂ O ₃ ≤ 5%  As will be described later, the flux of the present invention was previously disclosed in
Similar to the flux disclosed in No. -498, alloy composition range
Very good heat crack resistance by adjusting
One of the major features is that it can impart wear resistance and wear resistance.
It Therefore, without impairing such characteristics,
The method of improving the peelability of rug was examined.

In the examination, first, the slag forming agent and the tendency of seizure were investigated. As a result, they have found that the slag releasability can be dramatically improved by specifying a specific component. Specifically, first, Japanese Patent Laid-Open No. 3-49
In the flux disclosed in No. 8, limiting Al ₂ O ₃ to a certain amount or less leads to prevention of slag seizure. Al ₂ O ₃ has a function of increasing the melting point of slag,
Controlling this amount leads to a decrease in the melting point of the slag, and it is speculated that this also contributes to the improvement of the slag releasability.

However, when a flux having a low melting point and in which slag is hard to solidify is used in construction such as spiral heaping on a small-diameter roll, a phenomenon occurs in which the slag flows prior to solidification of the molten metal, which seriously hinders welding work. As the time comes, the bead shape becomes uneven, and other harmful effects occur. Therefore, it is also necessary to provide a means for preventing the adverse effect of the Al ₂ O ₃ amount regulation. And a component that can accelerate the solidification of slag and prevent the flow of slag even when performing spiral welding on a small diameter roll,
Moreover, MgO has been found as a component that does not impair the slag removability.

MgO enhances the melting point of the slag without impairing the slag releasability, promotes slag solidification, and contributes to the arc stability together with the formation of beads having a good shape. Such an effect is exhibited at 10% or more. To be done. However, if it exceeds 30%, the melting point of the slag is rather increased, and the slag is apt to be seized, and the linearity of the bead toe portion cannot be maintained, and there are problems such as generation of a pock mark. To make the effect of MgO more effective,
It is preferably 25%.

Al ₂ O ₃ is the biggest cause of increasing the melting point of slag and causing slag baking, and in order to avoid this, it must be suppressed to 5% or less. The slag releasability is further improved by preferably setting it to 3% or less.

10% ≦ 4 × Al ₂ O ₃ (%) + MgO (%) ≦ 40 (%) In the present invention, further, the amount of MgO and Al ₂ O ₃ is properly regulated to improve the peelability of the slag. Although it is possible to maintain them, both components have the effect of increasing the melting point of the slag. Therefore, unless the proportion of these components in the total is kept within a certain range, the effect of the component regulation cannot be effectively exhibited.

That is, both components accelerate the solidification of the slag, but in the above relational expression, when the amount exceeds 40%, the solidification of the slag becomes excessively fast, and significant slag seizure occurs and the bead shape is changed. It becomes convex and the risk of fusion failure increases. On the other hand, if it is less than 10%, the melting point of the slag is lowered, which causes adverse effects such as flowing molten metal and uneven bead shape. In addition, it is preferable to set the value of the above relational expression to 15 to 30% to prevent slag peeling and seizure, and to obtain a good bead shape.

Further, in the present invention, C, Ni and Mo are used.
And one or more of V, Nb, and W, and further Cu if necessary, by the alloy component amount (calculated value) [M] D of the weld metal represented by the following formula (1). It is added so as to satisfy a predetermined range.

[M] D = af × [M] f + aw × [M] w (1) Here, [M] D: content (%) of alloy component M in the weld metal [M] f: flux Content of alloy component M in alloy (%) [M] w: Content of alloy component M in wire (%) af: Yield coefficient from flux of alloy component M to weld metal aw: From wire of alloy component M Yield factor for weld metal

[C] D: 0.1-0.4% C prevents the formation of ferrite, which is harmful in terms of heat crack resistance and wear resistance, in the structure of the weld metal and forms a martensite structure. It has the effect of forming carbides with V and Mo to increase high temperature strength. To do this, [C]
The D content must be 0.1% or more, but if it exceeds 0.4%, hot cracking and cold cracking are likely to occur and the retained austenite increases.

[Ni] D: 0.5-3.5% Ni is an austenite forming element and contributes to martensite organization and toughness improvement of weld metal. Such an effect can be obtained by adding 0.5% or more of [Ni] D, but if it exceeds 3.5%, the coefficient of linear expansion becomes high and the heat crack resistance deteriorates.

[Mo] D: 0.5-2.5% Mo is effective in increasing high temperature strength and temper softening resistance, but for this purpose, the content of [Mo] D is 0.5% or more. There is a need to. However, if it exceeds 2.5%, since it is a ferrite-forming element, it is difficult to prevent the formation of ferrite, and the heat crack resistance is rather impaired.

[V] D, [Nb] D, [W] D : V, Nb, and W all form carbides by binding with C to increase high-temperature strength, resulting in heat crack resistance and It greatly contributes to the improvement of wear resistance. It also contributes to the improvement of temper softening resistance. Such an effect can be obtained by adding one of these components, but the effect is further increased by the combined addition.

However, in order to effectively bring out such an effect, at least one kind is 0.01% so as to satisfy the following expression in [V] D, [Nb] D and [W] D. It is necessary to add above. On the other hand, if one or more of these components are added in an amount exceeding 0.6%, the heat crack resistance is deteriorated due to the formation of ferrite and remarkable slag baking occurs. [V] D, [Nb] D, and [W] D are 0.06 to 2.2, respectively.
%, 0.02 to 3.0%, and 0.08 to 5.0 are desirable.

0.01% ≦ (1/4) × [V] D + (1/8) × [Nb] D
+ (1/15) × [W] D ≦ 0.6%

[Cu] D: 0.2-2% Cu is effective in maintaining the corrosion resistance to water and water vapor, but if [Cu] D is less than 0.2%, the effect is not sufficiently exhibited. If it exceeds 2%, the risk of hot cracking increases.

The above components are essential components in the present invention, and the degree of addition of the alloy component from the flux and the wire is not limited as long as it satisfies the above range.

The yield coefficient for each alloy component
(af, aw) cannot be uniquely determined because it varies depending on the constituent components of the flux, the basicity and the consumption rate, and the type of alloy component, but in the case of Ni, Mo, Nb and W, af: 0.3 to 1.2, aw: 0.5 to 1.0 in many cases, and C, V and Cu, af: 0.1 to 0.9,
aw: It is often 0.2 to 0.8.

If necessary, other components may be added appropriately. Typical components include deoxidizing agents such as Si and Mn, and further Cr and the like can be added.

Next, examples will be shown.

[0036]

[Example 1]

Using the fluxes of the components shown in Table 1 and the wires shown in Table 2, overlay welding was performed under the following conditions,
Workability was evaluated. Regarding the wire, W1 is a 13Cr-based solid wire, and W2 is a flux-cored wire in which a steel-based outer shell is filled with powder. Table 3 shows the calculated component values of the solid wire or the flux-cored wire expressed by the formula (1).

Welding condition base material: S25C round bar (200φ × 1000
L) Welding method: Submerged arc welding Polarity: DCEP Welding condition: 330A-23V-30cm / min Preheating / pass temperature: 200-350 ° C Lamination method: 3 layer welding Weld length: About 100mm

The workability was evaluated with respect to slag removability, slag baking, slag flow, bead shape, weld cracking, and undercut.

Next, in order to evaluate the performance, SM
Three or seven layers of weld metal were produced on the 490A base material under the above welding conditions and interpass temperature, heat treated at 600 ° C. for 2 hours, and then test pieces were taken. Chips for analysis and heat crack test pieces were sampled from the three-layer weld metal, and high-temperature tensile test pieces were collected from the seven-layer weld metal, and heat crack resistance and high temperature strength were evaluated, respectively.

The heat crack test is a method in which the surface of the test piece (third layer weld metal) is rapidly heated by the high frequency coil, then directly water cooled from the surface, and this is repeated 800 times.
The temperature of the surface of the test piece is heated between 150 ° C and 700 ° C.
Cooled. After the test was completed, the test piece was cut and the maximum crack depth in the cross section of the test piece was measured to evaluate the heat crack resistance. Fig. 1 shows the condition of the test piece and heating coil, and Fig. 2
Fig. 3 shows the thermal cycle pattern on the surface of the test piece, and Fig. 3 shows the shape of the test piece.

The high temperature strength was measured at 500 ° C. using a test piece having a shape conforming to JIS G 0567.

Regarding the evaluation criteria of each performance, both the heat crack resistance and the high temperature strength were compared with the conventional overlay welding materials.
It was supposed to be very good. That is, regarding the heat crack resistance, those having a maximum crack depth of 0.6 mm or less and a strength at 500 ° C. of 70 kgf / mm ² or more were accepted.

The evaluation results are summarized in Table 4, and all examples of the present invention had good workability and excellent performance.

On the other hand, in the comparative example, in terms of workability, C
In Comparative Example No. 9 in which the amount of O ₂ was insufficient, blowholes and pits were generated in the weld metal, and conversely, the amount of CO ₂ was excessive and ZrO
_In Comparative Example No. 10 in which the amount of ₂ was insufficient, the familiarity of the beads was significantly deteriorated.

Comparative Example N in which the amount of Al ₂ O ₃ exceeds 5%
In Comparative Example No. 11 in which the amount of O.10 or (4 × Al ₂ O ₃ + MgO) exceeded 40%, the slag removability was extremely poor, and significant slag seizure occurred. Further, in Comparative Example No. 11 having a high Cu content and Comparative Example No. 13 having a high [C] D content, hot cracking occurred.

Comparative Example No. 12 has a high ZrO ₂ content,
The bead was bent so much that it could not withstand spiral construction.

Comparative Example No. 13 having a high amount of SiO ₂ and Comparative Example N having an excessive amount of metal fluoride and an insufficient amount of MgO.
At o.14, a slag flow occurred, and as a result, the bead shape was uneven.

On the other hand, in terms of performance, Comparative Example No. 8 in which the value of formula A was too small was not sufficient in heat crack resistance and high temperature strength.

Comparative Example No. 14 in which the amount of [Ni] d is too small and the amount of [Mo] D is too large, and Comparative Example No. 14 in which the amount of [C] D is low and the value of A is high.
Then, the heat crack resistance deteriorated due to the precipitation of ferrite. In Comparative Example No. 14, the high temperature strength was also unsatisfactory.

In Comparative Example No. 9 in which the [Ni] D amount was excessive, the heat crack resistance was deteriorated due to the formation of retained austenite. In Comparative Examples No. 13 and No. 11 in which the amounts of [C] D and [Cu] D were excessive, hot cracking occurred.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

[Table 3]

[0055]

[Table 4]

[0056]

Example 2

Inventive Examples No. 1 and No. 2 in Example 1
And No. 5 were subjected to an oxidation test with high temperature steam. Test piece is 4t weld metal, 2t × 25w × 35L
Was collected in the size of. The test condition was 700 ° C. for 8 hours, and the increase in oxidation after the test was measured. Table 5 shows the test results.

No. 2 and No. 5 to which Cu was added in an appropriate amount
It was confirmed that the amount of increase in oxidation was small and good high temperature oxidation resistance was exhibited as compared with No. 1 in which No.

[0059]

[Table 5]

[0060]

As described in detail above, according to the present invention,
It is possible to perform welding with good workability even when welding work at high interpass temperature like a small diameter roll is unavoidable, and it has excellent heat crack resistance, wear resistance and corrosion resistance. Since the weld overlay metal is formed, excellent effects such as extension of life of hot rolls can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a situation of a heating coil and a test piece in a heat crack test.

FIG. 2 is a diagram showing a thermal cycle pattern.

3 (a) and 3 (b) are views showing the shape of a test piece, respectively.

[Explanation of symbols]

 1 Test piece 2 Heating coil 3 Thermocouple insertion hole

Claims (2)

[Claims] [Claim 1] wt% (hereinafter, the same) _{in, CO 2: 2.5~8.0%, CaO} : 5~15%, SiO 2: 15~30%, ZrO 2: 10~30%, metal Fluoride: 2 to 10%, MgO: 10 to 30%, Al ₂ O ₃ ≤ 5%, and the following formula: 10% ≤ 4 x Al ₂ O ₃ (%) + MgO (%) ≤ 40 %, And [M] D = af × [M] f + aw × [M] w (1) where [M] D: content of alloy component M in the weld metal ( %) [M] f: Content of alloy component M in flux (%) [M] w: Content of alloy component M in wire (%) af: Yield coefficient of alloy component M from flux to weld metal aw: Yield coefficient from the wire of alloy component M to the weld metal In the alloy component amount (calculated value) of the weld metal represented by the above formula (1), [C] D: 0.1 to 0.4% [Ni] D: 0.5-3.5% [Mo] D: 0.5-2.5 The content of C, Ni and Mo satisfying the above range, and for [V] D, [Nb] D and [W] D obtained from the above formula (1), 0.01% ≦ (1/4 ) × [V] D + (1/8) × [Nb] D + (1/15) ×
[13] Cr system or 17 characterized by containing at least one of V, Nb and W satisfying [W] D≤0.6%
Overlay welding flux used in combination with Cr-based flux-cored wire or solid wire. 2. Further, [Cu] D obtained from the above equation (1)
Regarding [Cu] D: 0.2% to 2%, Cu is contained, and the flux for overlay welding according to claim 1.