JPS589795A - Flux for submerged arc welding by belt-like electrode - Google Patents

Abstract

PURPOSE:To provide a flux for welding by which build-up layers of high toughness and high strength are easily obtained by slag making agents contg. specific amts. of CaO, CaF2, etc., by deoxygenizing agents for alloying agents contg. specific amts. of C, Si, Mn, etc.. CONSTITUTION:The flux contg. 5-25% CaO or CaCO3, 3-30% CaF2, 2-30% Al2O3, 3-30% MgO, 5-25% SiO2 as slag making agents, contg. <=0.5% C., 0.2- 3.0% Si, 1.9-11.5% Mn, 0.4-4.5% Ni, 1.3-10.2% Cr, <=40% iron as deoxygenizing agents for alloying and consisting of the balance unavoidable impurities is prepd. If necessary, it is possible to contain >=1 kind of <=3.6% Mo, <=5.7% V as alloying agents and further 1 or 2 kinds of <=15% TiO2 or ZrO2 as other components of the slag making agents.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flux suitable for band-shaped electrode submerged arc welding to obtain a build-up layer with excellent high-temperature toughness.
The object of the present invention is to provide a flux for submerged arc welding with a band-shaped electrode to obtain an underlay layer with excellent high-temperature toughness to prevent thermal cracks from rapidly propagating to the base metal.

Traditionally, various rolls and rollers used in steel mills, such as pinch rolls for continuous casting, hot rolling work rolls, table rollers, cold rolling work rolls, backup rolls, and continuous pickling pinch rolls, have been refurbished and repaired using the overlay welding method. This contributes to increasing the lifespan of products used.

However, in the case of these overlay constructions, many studies have been conducted on welding materials and welding methods to obtain the overlay layer that requires direct wear resistance, and although some results have been obtained, At present, not much research has been conducted on welding materials and welding methods for obtaining a welding layer for the purpose of improving the welding period.

For example, if a thin build-up layer is acceptable, welding can be performed directly with overlay material without using the underlay, or if a thick overlay is required, underlay welding can be done with a mild steel welding material, which is a so-called build-up material. After that, measures such as overlay welding are taken.

If the carbon equivalent of this base metal is high, if the overlay material is overlaid directly on the base metal, it is necessary to use low carbon mild steel or austenite to prevent cracks from occurring in the overlay layer due to carbon migration from the base metal. Measures such as underlaying with stainless steel materials are used.

The criteria for selecting such underlayment are the cost of the welding material and the prevention of cracking.In order to extend the service life, the wear resistance, cracking resistance, etc. of the overlay material should be checked. The main focus was on improvement.

However, with the trend of dramatic productivity improvement in recent years, operating conditions have become even more severe, and it has become necessary to fundamentally review the overlay technology in general.゛This is the reality! !
Taking the continuous casting pinch roll as an example, we investigated the factors that determine the length of the service life, and found that the hardness of the overlay layer is a major factor in the case of gradual wear starting from the surface.
Cracks that occur during use, scrapping due to thermal cracks, cracks in the case of breakage, and factors that affect the occurrence of thermal cracks include the cracking resistance of the overlay material and the heat cracking resistance, but this is the stage at which it grows significantly. In this case, the toughness of the underlayment material or base material is a major factor.If the underlayment material or base material has high toughness, the crack will not propagate deeply and the scales will not be used until the overlayment material is completely worn out. There was found.

On the other hand, it was also found that the worst case, the breakage accident, was mainly caused by a decrease in the toughness of the underlay material or the base material. still,
When we look at the case of underlaying with mild steel, the toughness is maintained at a certain level, but the strength is much lower than that of the overlaying layer and the base material, so it often cracks and breaks without being able to withstand the stress of thermal cracking. I found out.

The present inventors discovered that it is sufficient to increase toughness while maintaining strength at a high level, and as a result of studying slag forming agent components and alloy component systems, the present invention was completed.

That is, the gist of the present invention is to use CaO or Ca as a slag forming agent.
C0.5-25%, CaF25-25%, A12032
~30%, Mg03~30%, SiO□5~25% Also as alloying agent and deoxidizing agent CO15% or less, SiO,2~3
．． 0%, Mn 1.9~] 1.5%, NiO, 4~4
．． 5%, Cr 1.3 to 10.2%, iron content 40% or less, the remainder consisting of unavoidable impurities, or one or more of the following as an alloying agent: 3.6% or less Mo2S, 7% or less V or further contains 15 as other components of the slag-forming agent.
% or less of 'l'i02 or one or two of ZrO2
A strip-shaped electrode containing seeds is used for submerged arc welding flux.

The present invention will be explained in detail below.

First of all, (aCO3) acts effectively to shield the arc from the atmosphere with the reducing atmosphere of COt gas generated by thermal decomposition by the welding arc, and its decomposition product CaO protects against strongly basic slag. In this case, since it is submerged arc welding, the area around the arc is covered with flux, and the atmosphere does not necessarily need to be protected by strong CO2 gas, but rather CaO It is necessary to have an effect on the slag refining action.

If CaO or CaCO3 is less than 5%, no refining action can be expected and the yield of the alloy will be low. In addition, if it exceeds 25%, the slag itself becomes too basic and the viscosity of the slag increases too much, impairing welding workability, so the blending amount should be 5 to 25%.
%.

CaF2 is effective in lowering the melting point of slag and maintaining appropriate fluidity of slag by setting it at 5% or more.
If the content exceeds 25%, the arc tends to become unstable, so the content was limited to a range of 5 to 25%.

When the Al2O5 content is 2% or more, the slag shape becomes stable, and when overlay welding, the wetting angle between the base metal and the weld metal becomes smaller, which improves familiarity and is effective in preventing undercuts. If it is added to the slag, the melting point of the slag will increase, the fluidity will decrease, and the arc will become unstable, so the content was set at 30% or less.

MgO in a proportion of 3% or more can contribute to stabilizing the arc, improving slag releasability, and preventing undercuts, but a proportion of more than 30% may cause the bead shape to be disordered, so MgO in a proportion of 3 to 30% should be within the range.

When the SiO2 content is 5% or more, the fluidity of the slag becomes good and stable welding is possible, but when the Si02 content exceeds 25%, excessive St is included in the weld metal, which is not preferable.

Furthermore, one or more of Tt02 + ZrO2 can be added to the above-mentioned slag forming agent in order to maintain good fluidity of the slag, widen the peed width, and maintain good arc stability. It is effective in stabilizing the However, if it exceeds 15%, the fluidity of the slag becomes too high, and as a result, the slag tends to move forward, causing the bead shape to become disordered, so it is necessary to keep it below 15%.

Next, talking about the alloying agent and deoxidizing agent used in the present invention, first of all, C is an effective element for increasing the strength of weld metal when added in small amounts, but when contained in an excessive amount, it can cause a decrease in toughness. Assuming that the base material for overlay welding is often medium-high carbon steel, it is necessary to suppress the content to 0.5% or less.

Note that C is cast iron powder, chromium oxide, or an alloying agent containing C, such as Fe-Mn + Fe-8t + Fe-M
It is added in the form of o + Fe-Cr, etc.

In normal strip electrode submerged arc welding, 0.2% of St is necessary for deoxidation, but if it exceeds 3.0%, it tends to reduce the toughness of the weld metal, so it should be 0.
, 2-3.0%. In addition, SI is F
It is possible to add in the form of e-8t + 51-Mn + metal Si.

Regarding Mn, an amount similar to that contained in ordinary steel is required for deoxidation, and when added from flux, a minimum of 1.9% is required, but even if more than 11.5% is added, welding Since no significant improvement was observed in the mechanical properties of the metal, the content was limited to 1.9 to 11.5%. Note that Mn can be added in a form such as Fe-Mn+St-Mn.

Ni is an element that improves the toughness and impact value of weld metal, but when added in excess, the impact value decreases.

Figure 1 shows CaCO37% and CaF220 as slag forming agents.
%, AI! 20s 25%, Mg016%, 5i022
0%, before deoxidation 11, as alloying agent, CO, 1%, Mn
The basic components were 5% Cr and 6% Cr, and various Ni addition amounts were used in combination with a mild steel strip electrode (O, 4TxSO fighting width, 0.06%C, 0.29%Mn), and welding conditions were 900A. , 24V, 18cm/mix, and a preheating pass temperature of 150 to 200°C. A high-temperature impact test was conducted on an impact test piece taken from a six-layer weld metal, and the change in impact value at a test temperature of 200°C was observed.

As is clear from the figure, the addition of N1 contributes to improving the impact value of the weld metal, and a good value is shown with the addition of 0.4% or more Ni, but when the amount of Ni added exceeds 4.5%, the impact value of the weld metal increases. Since the impact value is low, the Ni content is limited to a range of 0.4 to 4.5%. Note that Ni is metal Ni + Fe-Ni
It can be added in the form of

Cr is an element necessary to increase the strength of weld metal,
In order to improve the strength, it is necessary to add 1.3% or more of Cr, but on the other hand, in terms of impact value, excessive addition of Cr is not preferable.

Second. The figure shows CaCO37% and CaF220 as sludge forming agents.
%.

U2os 25%, MgO 16%, 5i020%, deoxidizer, alloying agent, C011%, Mn 5%, Ni2
．． Using 5% as the basic component, and varying the amount of Cr added, mild steel strip electrodes (0.4t x 50mm width, 0.06%C
, 0.29%Mn), welding conditions 900A, 2
4V, 18 (In/order, preheating pass temperature 150~20
A high-temperature impact test was conducted on an impact test piece taken from a weld metal deposited in six layers at 0°C, and changes in impact value at a test temperature of 200°C were observed.

As is clear from the figure, the impact value shows a tendency to gradually decrease with the addition of Cr, but when the Cr content reaches ]0.2%, the decreasing trend is gradual and remains at a high level. %, the content of Cr decreases rapidly, so the range of Cr was set to 1.3 to 10.2%.

Note that Cr can be added in the form of metal Cr r Fe -Cr + chromium carbide.

One or more types of V can be added in an amount of 5.7% or less, and by adding these elements, it is possible to improve the strength level without further reducing the impact value of the weld metal. Note that Mo + V can be added in the form of metal Mo + Fa - Me + metal V, Fe-V, or the like.

In addition, when adding Si t Mrz Cr + Mos V etc. in the form of ferroalloy, the iron contained in these ferroalloys will of course become the iron source in the flux, but it will also affect the stability of the arc, the appearance of the bead, It is also effective to add iron powder alone, which is effective in improving compatibility with the base material. However, if the total iron content exceeds 40%, the bead appearance deteriorates, the slag removability deteriorates, etc., and this is not appropriate, so the appropriate content range is defined as 40% or less.

Next, the effects of the present invention will be explained in more detail based on examples.
At-ru.

The base material used in all tests was 545C shown in Table 1.
Welding was performed under the conditions shown in Table 2.

Table 1 Table 2 Table 3 shows the strip electrodes used. Also, in the fourth table, fluxes are shown all at once.

Table 3 Table 5 shows the results of welding a combination of the strip electrode shown in Table 3 and the flux shown in Table 4.

Fluxes F-8 and F-9 shown as comparative examples have poor welding workability because the blending ratio of slag-forming agent components is not appropriate.
The bead appearance was poor, the slag releasability deteriorated, and multilayer deposition was difficult, so subsequent tests were discontinued.

Fluxes F-10, F-11, and F-12 have good workability and enable sound welding, but the impact value of the weld metal is low because the blending ratio of alloying agent and deoxidizing agent components is not appropriate. It is difficult to say that it is low and practical.

F-137 Lux has good welding workability and the impact value of the weld metal maintains a high level, but its tensile strength is low due to the low blending ratio of alloying agents and deoxidizing agents, which also makes it difficult to put into practical use. It is hard to say that there is a sex.

In comparison, in the examples of the present invention, welding workability was good, and the impact value and tensile strength of the weld metal were able to maintain high levels, showing good results.

As explained in detail above, high toughness and high strength build-up layers can be easily obtained using the flux of the present invention, which has great significance.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the Ni content and the impact value of the weld metal, and FIG. 2 is a graph showing the relationship between the Cr content and the impact value of the weld metal. Figure 2 53

Claims (1)

[Claims] 1. CaO or CaC 0.5 to 25% as a slag forming agent;
CaF25-25%, A12os 2-30%, Mg0
3-30%, 5i025-25%, and as an alloying agent deoxidizer, C0.5% or less, Si0.2-3.0%, Mn1
．． 9-11.5%, Ni0.4-4.5%, Cr1.3
Flux for submerged arc welding with a band-shaped electrode, containing up to 10.2% iron and 40% or less iron, with the remainder consisting of unavoidable impurities. 2. CaO or CaCO35-25% as a slag forming agent,
CaF25-25%, A12os 2-30%, Mg0
3-30%, 5iOz5-25%, and as an alloying agent deoxidizer, CO35% or less, 8i 0.2-3.0%,
n 1.9-11.5%, Ni 0.4-4.5%, Cr
1.3 to 10.2%, iron content of 40% or less, and further contains one or more of the following alloying agents: 3.6% or less of Mo, 5.7% or less of V, and the remainder is unavoidable impurities. Slacks for welding. 3. CaO or CaC0.5-25%, C as a slag forming agent
aF, 5-25%, A40s 2-30%, MgO3
~30%, 81025~25%, and as an alloying agent and deoxidizing agent C0.5% or less, SiO, 2~3.0%, Mn 1
．． 9-11.5%, Ni 0.4-4.5%, Cr 1.
3 to 10.2%, iron content 40% or less, and 1 as a slag forming agent.
A flux for submerged arc welding with a band-shaped electrode, containing 5% or less of one or both of TiO2 or ZrO2, with the remainder being unavoidable impurities. 4. CaO or CaCO35-25%, C as a slag forming agent
aF25-25%, A12os 2-30%, Mg03
~30%, 5i025~25%, SiO2~3.0% as an alloying agent and deoxidizing agent, Mn 1.9~11.5%
, NiO, 4-4.5%, Cr 1.3-10.2%,
Iron content 40% or less, and CO as an alloying agent 15% or less, 3
．． 6% or less Mo, 5.7% or less V 181 or more, 15% or less Tie as a sludge forming agent, or 1 of ZrO2
A strip-shaped electrode submerged arc welding flux containing one or two species, with the remainder consisting of unavoidable impurities.