JPS62156097A - Low hydrogen type covered electrode - Google Patents

Abstract

PURPOSE:To inexpensively obtain a weld metal having good Charpy impact toughness at a low temp. and to obtain a welding rod which yields good beads by specifying the kind of the compounding components to constitute a covering material and setting the compounding ratios of the respective components to a specific range. CONSTITUTION:The covering material contains 13-23wt% titanium oxide in terms of TiO2, 0.1-8wt% total of >=1 kinds among Ti, Si, SiC, Mg, and Al, 0.05-2wt% oxide of boron or compd. thereof in terms of B2O3, 4-18wt% total of >=1 kinds among MgCO3, CaCO3, SrCO3, and MnCO3, 0.1-17wt% metallic fluoride, 1-15wt% SiO2, 9-22wt% MgO, 1-10wt% Mn, and 10-50wt% iron powder. The material satisfies the condition 5<=Y+2X<=16 when the content of SiO2 is designated as Y (wt%) and the content of a deoxidizing agent calculated by Ti+Si+SiC+Mg+Al as X (wt%); further the material contains 0.5-6.5wt% Ni. A binder is added to the covering material and the material is coated on a steel core wire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a low-hydrogen assisted arc welding rod that has good welding workability and low-temperature toughness.

[Conventional technology]

In recent years, with the development of energy resources in colder regions and deeper waters, welded structures have become larger and more sophisticated, and requirements for welded joints have become even more stringent. It is necessary to be good.

Under these circumstances, low-hydrogen based, low-Ni welding rods ranging from 0.5% Ni to 3.5% NS have been used to obtain welded joints with good low-temperature toughness. For example, as shown in Japanese Patent Application Laid-Open No. 58-138591, Mg
A low-hydrogen coated arc welding rod is known that has good bit resistance, good bead shape and bead appearance, and has excellent welding workability by adding SiC to a CO3-CaF2-based welding agent.

However, this welding rod is designed with emphasis on workability, so in order to ensure toughness at low temperatures, it is necessary to weld with a relatively low welding heat input to make the weld metal structure fine and to create high dust. In addition, the low welding heat input causes the problem of hardening of the heat-affected zone of the base metal. Sara K also,
Ni, which is used to obtain toughness, is expensive and the welding rod is expensive, making it uneconomical.

On the other hand, it was developed as a low-hydrogen coated arc welding rod that can be welded with normal welding heat input to obtain joints with good low-temperature toughness.
As shown in Japanese Patent No. 0-5397, CaC0-CaF
By adding Ti and B2O5 to the coating material of the system, appropriate amounts of T1 and B are contained in the weld metal, and
There are some products that achieve good low-temperature toughness by making the structure of the bath-welded metal uniform and fine-grained due to the effects of and B.

However, this welding rod has disadvantages such as poor welding workability and a convex bead shape, especially in horizontal fillet welding.

Furthermore, the present inventors have previously developed a method for obtaining good low-temperature toughness and preventing the bead shape from becoming convex.
No. 4997 was disclosed. This is mainly to improve the bead appearance and bead shape by controlling the amount of TlO2, carbonate, and fluoride, and we are looking at the effects of dekanashi.
Since this method requires the coating material to be more basic in the stomach, it is not always possible to obtain sufficiently satisfactory results in terms of welding workability (undercut resistance, slag peeling resistance).

[Problem that the invention seeks to solve]

The present invention provides a low-hydrogen coated arc welding rod that yields a weld metal with good low-temperature toughness and has excellent bead shape, bead appearance, and welding workability.

[Means for solving problems]

The present invention is a low-hydrogen coated arc welding rod developed as a result of various researches in response to the above-mentioned circumstances, and its gist is that titanium oxide is 13 to 23 in terms of TlO2. Weight %, 'l'i, Si.

The total of one or more of SiC, Mg, and AL is 0.1 to 8
weight%.

Boron oxide or boron oxide compound converted to B2O3, 0.05 to 2 layers, MgC0, CaCO3
゜S r COMn The total of one or more types of COs is 4 to 1
8 weight g H, metal fluoride 01-17 weight, SiO □ 1-15 weight Ji96, MgO 9-22 weight %, Mn 1-10 weight! )
%, iron powder 10-50 wt%, and 5IO2 content Y (wt%), Ti + Si + SiC + Mg + A
When the deoxidizing agent content calculated by l is X (weight S), the following condition is satisfied: 5≦Y+2X≦16, and NiO,
A low hydrogen-based coated arc welding rod is obtained by adding a binder to a coating material containing 5 to 6.5 hydrogen atoms and coating it on a steel core wire.

The feature of the present invention is that MgCO3 is the main component of the CO2 source, and by adding appropriate amounts of TlO2+ MgO and SiO2 to this, welding workability, bead shape, and bead appearance are improved. Furthermore, Ti, 81. By adding appropriate amounts of one or more of SiC, Mg, and At, KTl and B are uniformly dissolved in the weld metal to form a fine-grained, uniform structure, which significantly improves the low-temperature toughness of the weld metal. . That is, MgCo3-
Since the CaF2-based coating material has a larger amount of SiO2 added than the CaCO3-CaF2-based coating material and is more acidic, it has better welding workability as described above.

However, this coating material contains Ti, which is a strong deoxidizing agent.

By adding one or more of Si, SiC, Mg, and At, 5102 is reduced and 5iji in the weld metal is reduced.
The disadvantage is that it deteriorates the υ toughness. In order to prevent this phenomenon, the present inventors based on the above-mentioned knowledge, used SiO□ and Ti, St, SiC,
A comprehensive comparative study of the relationship between Mg and At revealed that by limiting the relationship between Mg and At to the range (B) shown in FIG. A low-hydrogen coated arc welding rod with excellent performance in bead shape, bead appearance, and welding workability can be obtained.

The present invention will be described in detail below.

[Effect]

Titanium oxides include rutile, illuminite, iron sand,
Titanium slag and the like are used, but in addition to the functions of slag generation, adjusting the viscosity of the slag, and improving the encapsulation properties of the slag, slag acid agents such as Sl, Mg, and AA are used.

It is added to reduce Ti in the weld metal by one or more of Ti and SiC, and if it is less than 13N in terms of TiO□, it has no effect, and if it is added in excess of 23i, it will reduce the fluidity of the slag. The range of 13 to 23 weight coefficient is appropriate because the slab will advance and the pead shape will deteriorate.

Ti, 81. SiC, Mg, and At have a strong deoxidizing effect and reduce oxides. Excluding TI (St, SiC,
Mg, At'Jl: By adding Mg and At'Jl to the coating, titanium oxide is reduced and an appropriate amount of Tl can be present in the weld metal without adding Ti itself to the coating.

In addition to deoxidizing, Ti is added to improve low-temperature toughness in relation to B in the weld metal;
81. If the total amount of one or more of SiC, Mg, and At is less than 0.1% by weight, there will be no effect, and if it exceeds 8% by weight, the fluidity of the slag will deteriorate, resulting in deterioration of the bead shape and hardening of the weld metal. Since low temperature toughness deteriorates, 0.1~
A range of 8 folds and 9% is suitable. In addition, Ti, St, M
g, At are Fe-Ti, Fe-8t, 51-Mn, At
-Added as Mg, etc.

The boron oxide or boron oxide compound is added to supply B to the weld metal and to improve the low-temperature toughness in relation to T1 in the weld metal. B2
The reason for adding from the coating in oxidized form like O3 is
This is because if B alloys such as Fe-B are added to the weld metal, segregation may occur and stable low-temperature toughness may not be obtained. Since the weld metal can be distributed, the structure of the weld metal can be made uniform. In this case, the same effect can be obtained even if the compound of boron oxide or sulfur oxide is added to water glass as a binder, stirred, uniformly dispersed or dissolved, and incorporated into the coating material. I'm sure you can get it. If the addition of boron oxide or boron oxide compound is less than 0.055% by weight (8203), the amount of B in the weld metal will be low and it will not be effective in improving low-temperature toughness, and if it exceeds 2% by weight, When B is added, high temperature cracking tends to occur when the weld metal contains a large amount of B, and low temperature toughness also decreases.

Note that the boron oxide or boron oxide compound herein refers to borax, anhydrous borax, natural borax, perovorite, kernite, and the like.

MgCO3, CaCO3, SrCO3, MnCO3 are
It acts as a gas generating agent and has the effect of removing weld metal from the atmosphere, and contains MgCO, CaCO3, Sr
If the total of one or more types of CO3゜MnC03 is less than 4N, shielding failure occurs, pits and blowholes are likely to occur, and the low-temperature toughness of the weld metal decreases due to the absorption of nitrogen gas.3 On the other hand, if the total of one or more types of CO3゜MnC03 is less than 4N, the low temperature toughness of the weld metal decreases due to the absorption of nitrogen gas. If added, the arc may become unstable and arc breakage may occur, and the viscosity of the slag increases, resulting in a convex bead shape.

Metal fluoride has the effect of reducing the amount of diffusible hydrogen in the weld metal and preventing the formation of pits and blowholes, and if the residual fluoride is less than 0.1% by weight, the above function will not be achieved significantly. As the amount of diffusible hydrogen increases, cracking resistance decreases, and pits and blowholes due to rust, oil, paint, etc. are more likely to occur. On the other hand, if it is added in excess of 17% by weight, the arc becomes unstable and the fluidity of the slag becomes excessive, deteriorating the bead shape. Here, A-based fluoride refers to CaF2. Na5AtF6. MgF2.
Refers to AlF2 etc.

SiO2 acts as a slag forming agent and a viscosity modifier, and has a particularly large effect on viscosity. If it is less than 1% by weight, the fluidity of the slab becomes unstable, causing deterioration in the appearance of the pead and the shape of the bead. becomes convex. On the other hand, 15
If more than 1 rust point is added, the slag becomes hard and peeling becomes difficult, and since it is an acidic oxide, the basicity decreases significantly and the toughness of the weld metal deteriorates.

MgO acts as a slag forming agent, a viscous lubricant, and a preservative, and improves the encapsulation of the slag. If it is less than 9% by weight, the above-mentioned effect will not be exhibited significantly, and undercuts will occur due to insufficient viscosity of the slag. On the other hand, if it is added in excess of 22% by weight, the viscosity of the slag will increase, the encapsulating properties will deteriorate, and the pead shape will become convex.

Mn td It is added as gold 1f + manganese or ferromanganese, etc., and is added to function as a deoxidizing agent or alloying agent, as well as to ensure arc strength and arc spread during welding, but it is added to If it is less than that, the mechanical properties of the weld metal cannot be sufficiently improved. On the other hand, if it is added in excess of 10% by weight, hot cracking will occur, so this is not recommended.
o Iron powder improves the arc rectangularity and increases the welding efficiency by increasing the amount of deposited metal, but if it is less than the IO weight ratio, the amount of welding is insufficient, resulting in poor pead elongation and poor welding efficiency. On the other hand, if it is added in an amount exceeding 50% by weight, the spread of the arc will be inhibited, and the encapsulating properties of the slag will be impaired, resulting in a convex bead shape.

Next, 5102 and the scleral acid agents Ti, Si, SiC, M
It is essential to specify the amount of g and At added in the weld metal. It was confirmed that the amount of Si should be taken into consideration. That is,
The N2 diagram shows the results of investigating the influence of Si on the vTra of weld metal. According to this, the St of the weld metal is 0.
It is clear that the low temperature toughness can be significantly improved in the range of 13 to 0.38%.

Therefore, based on the above findings, the present inventors investigated to confirm the appropriate range of quantitative balance between 5IO2 and the sclerotic acid agents Ti, St, SiC, Mg, and At. (weight%), and the scleral acid agent content X (weight i%) is X = T i + s i + S i C + Mg +
When Al Toshinoki 5≦Y+2X≦16 ・・・・・・・・・
...(1) It is necessary to add all the points. FIG. 1 is a graph showing the conditions of formula (1) and the conditions of the SiO
Both □ and the scleral acid agent satisfy the condition that they are below the upper limit, but Y+2X)16, which is an area where formula (1) is not satisfied. Part (B) in the figure is an area that satisfies all the conditions. In the same figure, part (C) satisfies the condition that both SiO□ and the sclera acid agent are equal to or higher than the lower limit, but Y+2X(5) indicates a region where (Equation 17 is not satisfied).

That is, in the same figure (B1 part h), not only a weld metal with good low-temperature toughness is obtained, but also the bead shape, bead appearance, and welding workability are extremely good.However, in the same figure (A) The area is Y + 2
There is a drawback that Si is excessively reduced and the amount of Si in the weld metal exceeds 0.38%, resulting in deterioration of low-temperature toughness.

On the other hand, in the same figure (0 part is Y + 2 Low-temperature toughness also deteriorates, making it impossible to achieve the intended purpose.

N1 is added to supplement the strength and toughness of the weld metal, and these effects are not effectively exhibited if the weight factor is less than 0.5. However, these effects reach a saturation state at a weight value of 6.5, and even if the content exceeds this level, the toughness hardly improves, and welding workability deteriorates on the contrary. The beads containing the above-mentioned components can be manufactured by coating a steel core wire with an adhesive such as water glass and drying it according to the usual welding rod manufacturing process.

In addition, the hook core wire used in the welding rod of the present invention is JIS G
Insert the core wire corresponding to Part 1, No. 1 of 3523.

Next, the effects of the present invention will be described in more detail based on Examples.

〔Example〕

As shown in Tables 1 and 2, an appropriate amount of water glass was mixed into coating materials with various compositions, and this was coated on a mild steel core wire of fc5mφ x 700mm, dried at a maximum temperature of 400℃, and the welding rod A- 1
- A-8, B-1 to B-11 were prototyped.

Using the above-mentioned sample rod, a root gap of 1 to 3 was taken on an aluminum guild steel plate with a thickness of 20 m with a V-bevel with a groove angle of 50', and downward welding was performed at a welding current of 22 OA and a welding heat input of 18 KJ/
It was done in cm. After that, the bottom 2 of the plate thickness surface on the final pass side
A 2 rmV notch Charpy palm impact test piece was taken from m and tested at -60°C.

The welding workability test was carried out using a steel plate (16 mm thick) coated with a wash primer of 20 μm on the surface in a horizontal fillet position at a welding current of 230 A and a rod operation ratio of 1.3.

The criteria for evaluation was that an impact value of 5 cm or more at -60°C was considered good. In addition, the O mark for welding workability means good, the Δ mark means slightly poor, and the X mark means completely poor.

Examples A-1 to A-8 of the present invention are all examples that satisfy the requirements of the present invention, and are extremely excellent in both welding workability and impact value of the weld metal.

Comparative Examples B-1 to B-3 were Y+2X(5), and were poor in both customer handling workability and low-temperature toughness. In case B-1, the amount of titanium oxide added was small and the bead shape was poor.

In B-2, the amount of titanium oxide added was large, the fluidity of the slag increased, and the bead shape became convex. B-3 is MgC0,
Bits were generated due to the small amount of addition. Furthermore, the amount of Ni added was large, and the arc condition was poor. B-4 is Y+2X)16
Therefore, although welding workability is good, the amount of St in the weld metal exceeds 0.38% and low-temperature toughness is poor.

B-5 has a large amount of MgCO3 added, has a bad arc condition, bad beat shape, and is Ti.

Since St, SiC, Mg, and At are not added, TI is not retained in the weld metal and low-temperature toughness is poor. B-5 is Mg
The amount of added O is small, causing undercutting, and the amount of added Mn is large, resulting in poor mechanical properties. Also, the amount of iron powder added is small and the beet spread is poor. B-7 had a large amount of CaF 2 added, poor arc condition and bad beat shape, and had a small amount of Mn added, resulting in poor mechanical properties. B-8 has a large amount of Mg added, resulting in poor slag fluidity and poor bead shape, and hardening of the weld metal, resulting in poor low-temperature toughness. Also, the amount of iron powder added is large, causing poor arc spread. B-9 has a large amount of MgO added, which increases the viscosity of the slag, resulting in a bad bead shape.
Since a2B4O7aB203 is not added and there is no B in the weld metal, the low temperature toughness is poor. B-10 is CaF25
NaμJF'6'f.

Since no additive is added, the pitting property is poor, and the amount of 5IO2 added is large, resulting in poor low-temperature toughness. B-11 has a large amount of B2O3 added, resulting in too much Bq in the weld metal, resulting in poor low-temperature toughness, and a small amount of 5IO2 added, making the slag fluid state unstable, resulting in poor bead appearance and bead shape.

〔Effect of the invention〕

As described above, the welding rod of the present invention is safer than conventional welding rods and has Charpy resistance at low temperatures by specifying the types of compounded components that make up the coating material and setting the compounding ratio of each component within a specific range. It is possible to obtain a weld metal with a good value and dust content, and to satisfy bead shape, bead appearance, and other welding performance, and to greatly contribute to the safety of offshore structures and other structures. The industrial effects are extremely significant.

[Brief explanation of drawings]

Figure 1 shows the 5lO2 content and Ti, St, SiC
, Mg, and At content. FIG. 2 is a graph showing the relationship between vTrs of the weld metal and Slf in the weld metal.

Claims (1)

[Claims] 13-23% by weight of titanium oxide in terms of TiO_2
, the total of one or more of Ti, Si, SiC, Mg, and Al is 0.1 to 8% by weight, boron oxide or boron oxide compound is 0.05 to 2% by weight in terms of B_2O_3,
MgCO_3, CaCO_3, SrCO_3, MnCO
_4 to 18% by weight of one or more of 3, 0 metal fluorides
．． 1-17% by weight, SiO_21-15% by weight, MgO
9-22% by weight, Mn 1-10% by weight, iron powder 10-50
% by weight, and the content of SiO_2 is Y (% by weight)
, 5≦Y+2X≦16 when the deoxidizer content calculated by Ti+Si+SiC+Mg+Al is set to X (weight%)
1. A low hydrogen-based coated arc welding rod, which satisfies the following conditions, and is made by adding a binder to a coating material containing 0.5 to 6.5% by weight of Ni, and coating the steel core wire with the coating material.