JPS59163098A - Low hydrogen coated electrode - Google Patents

Abstract

PURPOSE:To provide a titled electrode suitable for welding low temp. steels by binding a steel core wire contg. C in a specified amt. and a coating material contg. specifically composed Mn, B, Si, Ti, Ni, CaF2 and CaCO3 or BaCO3. CONSTITUTION:A low hydrogen coated electrode is obtd. by binding a steel core wire contg. 0.02-0.06wt% C and a coating material contg. 0.7-7% Mn, 0.01- 0.03% B, 4-6% Si, 0.3-1.5% Ti, 6-10% Ni, 10-18% CaF2 and 45-65% CaCO3 and/or BaCO3, in a coated electrode formed by depositing the coating material contg. a slag forming agent, arc stabilizing agent and binder together with a metallic powder agent on the steel core wire. Such welding rod forms a weld metal having good toughness to fracture and excellent low temp. toughness when used for welding low temp. steels.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a low-hydrogen coated arc welding rod, and is particularly suitable for welding low-temperature steel that requires excellent low-temperature toughness and a high COD value. This is an attempt to propose a coated arc welding rod.0 (Problems with the prior art) In coated arc welding bodies for low temperature steel, N is generally contained in the weld metal.
A material with an i of 2.5% to 8.5% was used, and low-temperature toughness could be secured to some extent.

However, in recent years, the performance of weld metal is often evaluated based on fracture toughness value (00D value: δC), and 2.5%
Weld metal using a conventional welding rod of N1 thread and 8.5% Ni thread has a limit 00D value δC at -60°C and -80'C.
This has become a problem as the range between 0 and 25 cannot be satisfied.

(Objective of the invention) The object of the invention is to
To provide a low hydrogen-based coated arc welding rod that is improved so as to always ensure the limit COD value δC0,25is.

(VJ machine of the invention) Needless to say here again, the COD value is an evaluation of the bending ductility of the notch tip, and reducing the amount of carbon is the most effective way to increase this. In this invention, since the amount of Ni is effective, we lowered the carbon content compared to the conventional method, and conducted the following development research on a coating composition suitable for this.

In other words, the limit COD value δCO, 25°C is -60°C.
The amount of carbon in the core wire to maintain temperature at 80°C is 0.02~
Weld metal reduced to 0.06% (conducted 30D test,
-60'C as calculated according to B5l5762.

Limit at -80''C (30D value is 2.5% Ni system, 8.
#JJ revealed that a Q value of 5 am or more can be obtained for both 5% Ni systems.

Furthermore, as a result of investigating the toughness associated with carbon reduction, it was found that the toughness also improved as the amount of carbon was reduced.

(Structure of the Invention) Based on the above findings, the present invention provides a coated arc welded body in which a steel core wire is coated with a coating material containing a slag forming agent, an arc stabilizer, and a fixing agent together with a metal powder. The carbon content was 0.02 to 0.06% by weight (hereinafter simply referred to as %), and the coating material contained In: 0.7 to 7.
%, B: U, 01-0.08%, si: 4-6%
, Ti: o, s~1.5% and Ni: 6~1O%
The above-mentioned problem has been advantageously achieved by providing a low-deformity filament-covered arc welding shell which is a combination of containing OaF: 10 to 18%, caco8 and/or BaOO, 45 to 60%.

(Experiment history) Now, the outer diameter 4 wisteria φ length 40 with the chemical components shown in Table 1
The two types of core wires of 011114 have the chemical composition shown in Table 2.
Each type of coating material was applied using a welding rod coater to give a coverage of 58%, and after being dried at 400'C for 1 hour, test rods were prepared.

Next, a low-humidity steel containing 3.5% Ni with a plate thickness of about 82 mm was prepared with a groove as shown in Fig. 1, and the welding body was welded in a vertical position with a welding current of 17 OA and a welding heat amount of 3 sKJ/cm. Table 3 shows the results of a three-point bending COD test using these test pieces.

Test piece i1 has a core wire with a carbon content of 0002% and a coating material containing 6% N1; test piece i1 has a carbon content of 0002% and a Ni content of 9%; The carbon content is 0006%, the Ni content is 6%, and the same is /164.
The carbon content is 0.06% and the Ni content is 9%.

As shown in Table 8, the COD test results of these test pieces showed that the limit 00D value was 0 at -60°C and -so'c.
．． Good tearing with 5rILtlL or more.

In addition, the absorbed energy values of the 2 m V notch Charpy test conducted in conjunction with this test were all 8. as listed in Table 8.
(lIc9f-m or more, which was good) In other words, if the carbon content of the core wire is 0.02% to 0.06%, the limit (300 value is Q ,5
It was found through the above experiments that it can be done for more than ms.

It is thought that an improvement in the COD value can be observed even if the carbon content of the core wire is lower than 0.02%, but if the carbon content is lower than 0.02%,
Reducing the carbon content to less than 0.06% is not a good idea as it will increase industrial costs.On the other hand, if the carbon content exceeds 0.06%, it is no longer possible to improve the COD value...6, so the carbon content of the core wire was limited to 0.02 to 0.06%.

Next, the reasons for limiting the ingredients of the coating material are explained. OIn is added to improve toughness, but if it is less than 0.7%, no improvement will be observed, and if it exceeds 7%, it will cause low toughness. Therefore, it was limited to 6.7 to 7%.

B is added as a toughness improving element, but if it is less than 0.01%, there will be no improvement, and if it exceeds 0.08%, the effect will be saturated and no further improvement in toughness will be observed, so 0.0
It was limited to 1 to 0.03%.

Si is added as a deoxidizing agent, but if it is less than 4%, deoxidation is insufficient and welding workability deteriorates, while if 6% is added, Si in the weld metal increases and the toughness deteriorates.
It was limited to 4-6%.

T1 is added for the purpose of improving toughness by refining the secondary structure of the weld metal, but if it is less than 0.8%, the effect is small, and if it exceeds 1.6%, it will not improve the structure. Even if the effect is recognized, the amount of inclusions increases and the toughness deteriorates, so Ti was limited to 0.3 to 1.5%.

Ni is an element that improves low-temperature toughness in the range of 60°C to -80'C (7).
If it is less than 10%, the effect will be small, but if it is more than 10%, the low temperature toughness will be even better, but from 60°C to -8
To ensure toughness in the 0″C range (Ni is 6% to 10%
This limitation was made because % is sufficient.

0aF2 increases the fluidity of the slag and improves the fire resistance of the coating material, but if it is less than 10%, the slag has poor fluidity and workability is poor, so 10% is the lower limit, while if it exceeds 18%, the fluidity of the slag is poor. The upper limit was set at 18%, since excessive carbon content would actually worsen workability.

0a (308j=3 and the addition of carbonate of BaO08 is C
02, which has a shielding effect of protecting the weld metal from the arc atmosphere and an effect of reducing the amount of dispersion and diffusible hydrogen of the weld metal. However, if the total of one or two types of 0aOO, BaOO8 is less than 45%, the effect is small, and 6
If it exceeds 0%, the fluidity of welding slag will drop significantly and workability will deteriorate, so it was limited to a range of 45 to 60%.

(Example) A low-temperature steel containing 8°5% Ni with a plate thickness of 82mm was coated with two types of coating materials listed in Table 2 for each core wire with the composition shown in Table 4, with the groove shown in Figure 1. The welding conditions were as follows:
Welding current: 17 U A% Welder's heat consumption: 88 KJ
/cm vertically welded 000D test pieces were taken, and an 8-point bending COD test was conducted using these test pieces. The results are shown in Table 5.

Table 5 shows the results of Table 8 according to the present invention for test pieces tVx 1~
/As reposted for I64, all have good limit C
The OD value was obtained, and the 2+as V notch absorbed energy of the weld metal was 8.0 kgf-m or more, which was good. However, for reference, types (3) to 4 in Table 4 were used.
Test piece doors 5 to 1612 using the core wire of (6) are all at the limit (E
OD, 600.25 m5 is not satisfied (as the amount of carbon in the core wire increases, the value decreases. Furthermore, the notch Charpy absorbed energy is often 8.0 kgf-m or less. It was found that the toughness significantly decreased as the amount of carbon in the core increased.

It is clear from the above comparison that when welding is performed using the welding rod of the present invention, a weld metal with good fracture resistance and low-temperature toughness can be obtained, thereby improving the safety of welded structures.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the weld joint groove shape.

Claims (1)

[Claims] 1. A coated arc welding rod in which a coating material containing a slag forming agent, an arc stabilizer, and a fixing agent together with a metal powder is applied to a steel core wire, and the carbon content of the core wire is 0.02 to 0.02. In the coating material, In: 0.7% by weight, B2: 0.01 to 0°03% by weight, Si: 4% by weight.
~6% by weight 'I'i: 0.3-1.5% by weight and yi: a
~10% by weight and 0aF2: 10~18wt 41% 0a00 and/or Baao8415~a o wt%. A low water chart coated arc welding rod.