JPS6044197A - Low hydrogen type coated arc welding rod - Google Patents

Abstract

PURPOSE:To improve a characteristic to generate low-temp. brittle fracture and low-temp. toughness by coating a coating material contg. a specific amt. of Al, Si, etc. on a mild steel core wire thereby forming a low hydrogen type coated arc welding rod. CONSTITUTION:A low hydrogen type coated arc welding rod is formed by coating a coating material contg. 0.5-7.0% Al, 0.1-4.0% Si, 3.0-7.0% Mn, 0.01- 0.03% B, 10-18% CaF2 and 45-60% in total of 1 or 2 kinds of CaCO3 and BaCO3 on a mild steel core wire. The content of Si in the deposited metal is thus decreased and the characteristic to generate low-temp. brittle fracture is improved. Since Al deoxidation is effected, low-temp. toughness is improved as well.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low-hydrogen coated arc welding rod used in coated arc welding.

For example, weld metal in welded parts of welded structures such as spherical tanks for LPG storage is required to have properties such as low compatibility and resistance to low-temperature brittle fracture, and coatings that can obtain such weld metal are required. Arc welding rods have long been desired.

However, in reality, even if the composition of the core wire of the welding rod and the composition of the core wire coating material are improved, there is a demand for good low-temperature toughness of the weld metal, and a property that low-temperature brittle fracture is unlikely to occur, that is, low corrosion resistance. It is actually difficult to satisfy the requirement of good fracture occurrence characteristics (COO value) for the load, and if low-temperature toughness is made good, there will be problems with low tA and WA fracture occurrence characteristics. On the other hand, if the low temperature brittle fracture occurrence characteristics were to be improved, there would be problems with low temperature toughness, which is problem B.

The present invention has been made in view of the above-mentioned conventional conditions, and is based on a low-hydrogen-based weld metal that can improve both the low-temperature toughness and the low-temperature brittle fracture occurrence characteristics of weld metal. ! ! The purpose is to provide a covered arc welding rod.

As a result of various studies to achieve the above-mentioned object, the present inventors have appropriately adjusted the composition of the coating material forming the low-hydrogen-based coated arc welding rod, and performed welding using the welding rod. If the amount of Si in the weld metal is reduced by this and ^Q acid is applied to the interlayer, C0DllI can be improved by reducing the amount of Si, and the
The inventors have discovered that by deoxidizing the weld metal, the structure of the deposited metal can be improved and its cleanliness properties can be improved, leading to the creation of this invention.

That is, the low hydrogen-based coated arc welding rod of the present invention has 8Q
0.5-7.0%, Si O,j-4.0%), I
n 3.0 to 7.0%, B 0.01% to 0.03%,
ca F2 10-18%, Ca CO3 and Ba C
It is characterized in that it is made by coating soft p-core cotton with a coating material containing a total of 45 to 6096 of one or two of O3.

First, the purpose of adding each component of the coating material used in the low-hydrogen coated arc welding method of the present invention and the reason for limiting the amount added will be explained.

k(n: Added in an amount to improve hardenability and improve the structure, thereby improving the toughness of the weld metal.

A good amount is 3 to 7%, and no improvement in toughness is observed when the amount is less than 396, and adding more than 7% results in excessive disk quenching, resulting in a decrease in the toughness of the weld metal.

B: Added to microphase the structure and improve toughness. The range of 0.01% to 0.03% is good, and the range of 0.01% to 0.03% is good.
If it is less than 0.01%, there is no substantial effect on improving dust 11, and 0.
．． Even if it exceeds 0.3%, there is no improvement in the toughness improvement effect.

CaF2 varnish slag flow a (1 and coating resistance 9 ()
1 is added to L"4'll. The addition r is preferably in the range of 10 to 18%. If it is less than 10%, the slag will have no fluidity and workability will deteriorate. If it exceeds the limit, the fluidity of the slag becomes excessive, which significantly impairs workability, impairs the formation of an arc-holding tube, and increases spatter.

ca COa and 13a CO3 and 1 or 2 types: These additive components decompose during welding to produce CO2, and the CO2 has a shielding effect of protecting the WN2 metal from the arc atmosphere, and also +FJ is added to the effect of reducing oxygen levels and diffusible hydrogen in i8 metallurgy disease. One or two types of Ca CO3 and Ba CO3
The total addition of fl is 45-60%, which is 45%.
If it is less than 6096, the effect of addition is not so great, and if it exceeds 6096, the welding workability deteriorates considerably.

Si to he Q: Together! Added as lQ'M agent. The inventors of the present invention conducted the following test after the amount of addition was 1 trough, and based on the findings obtained, the present invention was completed.

The contents of the test are soft persimmons of a certain composition) An 'l'
) Butt welding obtained using a low-hydrogen coated arc welding rod coated with coating materials of various compositions with different amounts of 8Q and Si additions while keeping the amount of other components such as B constant. This test evaluates the low-temperature toughness and low-11 fracture occurrence characteristics of welded metal.

The composition of the core wire used in the trial M welding is shown in Table N1, and the composition of the various coating materials is shown in Table 2.1゜A core wire formed with the composition shown in Table 1 and having a diameter of 4 mm and a length of 400 mm. second to
Which coating materials are best shown? ! ! ! The welding rod was coated with a coverage of 58% and then dried at 400° C. for 1 hour to obtain a test welding rod. Using this welding rod (X), we butt-welded a 25 mm thick low-temperature aluminum killed plate.

The welding base material is shown in the first time, Ll in the figure is 25 mm, 1-2
is 13111111. L3 is 2111m, 14 is 10m
m,, Ls is 2 mm, αl is 70°, α2 is 90
'is.

The welding conditions were as follows: the welding position was vertical, the welding current was 16OA, and the welding person was ff! tffi was set to 38 KJ/cm.

The welded metal scraps of the butt welded materials obtained as described above were evaluated for their low temperature toughness and low +gR fracture occurrence characteristics.

Low-temperature toughness was evaluated based on the absorbed energy value at -45°C. Its evaluation convexity is 10kof-m
A value of 10 kQf'-m or more was considered good. In addition, regarding the brittle fracture occurrence characteristics, the limit COD at -45℃
It was evaluated by li1m (δC). The evaluation criteria were o, 4 mm, and those of 0.4111 m or more were considered good. In addition, the COD test station conforms to BSI standard B55762-1.
It was carried out according to 979.

The test was conducted by taking a JIS Z3112 4 @ impact test piece from a part 1 m in the plate thickness direction from the surface of the butt welded material obtained as described above, and collecting COD test pieces from all parts in the plate thickness direction. . The notch position of the COD test piece was at the center of the welded metal scrap, and the plate thickness was n.

Table 3 shows the results of each of the above tests.

The test pieces indicated by 1111 and 11α2 in Table 3 are test pieces obtained using welding rods using coating materials indicated by tlol and tlo, 2 in Table 2, and similarly Hp, 3.
The test pieces indicated by ~1106 are No. 3~ in Table 2.
Fig. 6 shows a test specimen prepared using a welding rod with a coating material shown in Fig. 6.

As shown in Table 2, the coatings of )io, 1 and)Il12 had a 5iffi addition of 6 and 0g6.4 respectively with the addition of AQ1.
．． It is set at 8%. Test obtained for that coating! , 1 piece of tia 1 and NO, 2 have an average absorbed energy of 18.8 kg each at 45°C, as shown in Table 3.
f-m and 20, 8 kg, and f-m, which was good. However, the limit C of those specimens at 45℃
The OO value (δ0) is minimum: 0.212 and 0.2, respectively.
00, it was defective. In addition, the coating materials No. 1103 to No. 16 were added with AQ in the range of 0.5 to 7% and Si in the range of 0.4 to 4.0%, and the test pieces obtained for these test pieces were k3 to HO6-45℃T:'f) Suction VR
Energy = Lt16.9~22.9kgf-m,
Also, the minimum COO value is 0.40+i~0.651
m1M, and better results than the evaluation criteria were obtained in all cases. From this result, the addition of Si is 0.1%.
~4.0%, Al! It is clear that the amount of Si added is preferably in the range of 0.5 to 1.0%. That is, if the amount of Si added is less than 0.1%, workability deteriorates due to insufficient deoxidation, If it exceeds 4.0%, Si in the middle of the deposited gold
However, the dust becomes excessively high and the dust fl decreases.

Al again! If the amount of A9 added is less than 0.5%, deoxidation will still be insufficient, and even if 7.0% is added in addition to I, the effect of adding A9 cannot be increased.

The coating material used in the low-hydrogen coated arc welding of this invention is the aforementioned △ρ, Si,! ,4n,R,CaF
2. In addition to ca CO3 and Ba CO3, the remainder usually contains an arc stabilizer and a fixing agent as in conventional products. Here, the arc stabilizer is T*02. It is possible to contain about 1 to 4% of 20, Na2O, etc., and furthermore, Na, Li, etc. can be contained as a fixing agent.
Water glass containing, for example, can be used.

Examples and comparative examples of the present invention are described below. Using the low-hydrogen-based coated arc welding rod of the present invention, temporary welding of low-temperature aluminum killed aluminum ξ1 having the shape and dimensions shown in FIG. 1 was carried out. Welding was performed in a vertical position, and the welding current was 160A.
Welder Netsuta had 38 kJ/'cmte'jJ5.

Comparative example Si was added in an amount of 4.0% or more, and a pond δ agent without Q was added.
Low hydrogen obtained by painting zeta core wire? ! ! Welding was carried out in the same manner as in the example using covered arc welding.

Table 4 shows the compositions of the coating materials of Examples and Comparative Examples. In the table? 1α1 to Nα4 are the compositions of the coating materials of the examples, NO, 5
~! -108 shows the composition of the coating material of the comparative example. In addition, Table 5 shows the chemical composition of the obtained molten metal for each of the Examples and Comparative Examples.

■50% to the ratio of Fe-∆Ω medium Q For each of the examples and comparative examples, JIS Z3112 No. 4 from a position that protruded 1mmr1M in the plate thickness direction from the surface of the butt welded material! ii Take the impact test piece and perform COD test from the entire plate thickness direction! ! Now collect the piece and -45℃
We investigated the absorbed energy of Ryu and COO can. The results are shown in Table 6.

As shown in Table 5, each weld metal deposited according to the comparative example contains 0.40 to 0.50% Si, whereas the Si content of each weld metal determined according to the example 0
．． It can be seen that the amount of Si-containing tufts in the weld metal is significantly reduced in the actual melting example. In addition, in the case of the sea urchin shown in Table 6, -45
The absorbed energy at IJ at ℃ is 10 kgf −
m (O Piip IF-) In addition, both of the limit COD values exceeded 0.4 m1 (evaluation criteria *> or higher, low temperature toughness, low temperature P~). I can see that you are getting money and a place to live. In contrast to this machine, this is the case in the comparative example! ! Both energy is 10k
It is above gr-m (Taiwan standard) and satisfies the requirements, but the limit COD Vi + 2 is much smaller than the evaluation standard, and it is low humidity F! It can be seen that this is a small-size Aro welding table IL in terms of breakage occurrence characteristics.

As described above, according to the present invention, 8Q is 0, 5''-
By coating a mild steel core cotton with a coating agent containing 7.0% and 0.1 to 4.0% Sl, a low-hydrogen coated arc welding rod is produced, reducing Si in the weld metal and reducing low-temperature embrittlement. The fracture occurrence characteristics can be improved, and AI'l! ! By performing this process, even low product toughness can be improved.

[Brief explanation of the drawing]

FIG. 1 is a side view showing the shape and dimensions of a base material to be welded. Applicant Kawasaki Steel Co., Ltd. Agent Patent attorney Takehisa Toyota (and one other person)

Claims (1)

[Claims] 8Q 0.5-7.0%, Si 0.1-4.0%, M
n 3.0 to 7.0%, B 0.01% to 0.03%,
10-18% ca F2, ca C03 and BaCO
1. A low hydrogen-based coated arc welding rod, characterized in that a soft core wire' is coated with a coating material containing a total of 45 to 60% of 2I or 2I.