JPS5913954B2 - Covered arc welding rod - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coated arc welding rod that maintains the characteristics of titania-based welding rods and improves its continuous performance, particularly its cracking resistance, which has been considered a drawback.

Titania-based coated arc welding rods have many advantages, such as 1) less spatter, 2) excellent re-arcing properties, 3) beautiful bead appearance, and 4) ability to perform vertical downward welding, increasing welding efficiency. have. However, its application was limited to welding thin plates because it had the disadvantage of poor joint performance, particularly cracking resistance. However, in view of the above-mentioned characteristics of titania-based welding rods, it would be extremely meaningful to improve their cracking resistance and make them applicable to thick plates. Under the above-mentioned circumstances, the present invention aims to improve the cracking resistance of weld metal while maintaining the advantages of titania-based welding rods.
In particular, it was completed as a result of intensive research from the aspect of the component composition of the coating material, and its composition is TiO2: 35 ~
57%, SiO2: 15-28%, Al2O3: 3-8
%, Mn: 2.5-9%, MgCO3 and/or C
aC03: 3-10%, organic matter: 1-8%, ZrO2:
0.3 to 6%15, and (TiO2+ Z
The gist is that a coating material having a weight ratio given by rO2)/(CaC03+MgC03) within a range of 5 to 18 is applied to the outer periphery of a mild steel core wire. The basis for setting the numerical range in the present invention will be described below.

1TiO2: 35-57% This is an essential component for adjusting slag encapsulation, slag fluidity, etc. and ensuring good re-arc properties and bead appearance, which are the characteristics of titania-based welding rods. Below these characteristics, these characteristics will not be exhibited significantly.

However, if it is too large, the slag removability deteriorates and work efficiency decreases, so it should be kept at 57% or less. 2510
2: 15-28% 30 It has a function to adjust the slag viscosity and arc blowing strength, etc. If it is less than 15%, the arc blowing is weak and slag is likely to get caught.

On the other hand, if it exceeds 28%, the arc voltage becomes too strong and an undercut occurs. 353Al2O3: 3-8% Adjusts the viscosity of the slag, improves the appearance of the bead, and promotes the formation of spray arcs.

If it is less than 3%-n, these effects are insufficient, and if it exceeds 8%, the arc spray becomes coarse and spatter increases.

4Mn: 2.5 to 9% It is blended in the form of metal Mn or Fe-MnlSi-Mn and functions as a deoxidizing agent.

If it is less than 2.5%, blowholes tend to occur due to insufficient deoxidation, and the X-ray performance of the weld metal deteriorates.

On the other hand, if it exceeds 9(X), excessive deoxidation causes frequent pitting. 5cac03 and/or MgCO3: 3-10
% This is a component that acts as a gas generating agent and protects the weld metal from the atmosphere. If it is less than 3%, pitting will occur due to insufficient shielding, while if it exceeds 10 (fl), the arc will become unstable and arc breakage will occur. This occurs frequently, and undercuts are more likely to occur.

6 Organic matter: 1 to 8% It functions as a gas generating agent and improves re-arc properties, and these effects are not significantly exhibited if the content is less than 10I).

Moreover, if it exceeds 8%, the arc spray becomes excessive, resulting in defects such as frequent occurrence of undercuts and spatters. 7Zr02: 0.3-6% ZrO2 is a high melting point compound and is an essential component for strengthening the protective tube during welding and making use of the characteristics of vertical downward welding, which is a feature of titania-based welding rods.

That is, in vertical downward welding using a titania-based welding rod, the bead shape varies considerably depending on whether contact welding is performed or not. If contact welding is not possible, the first
As shown in Figure a, the bead becomes concave and multi-layer welding is required to satisfy the design strength, reducing welding efficiency.
The advantages of vertical downward welding are diminished. On the other hand, when contact welding is performed, a better bead can be obtained by welding as shown in FIG. 1b, so that the advantages of vertical downward welding can be effectively exhibited. In other words, enabling contact welding is
This is an essential requirement to take advantage of the advantages of vertical downward welding, and for this purpose a suitable protective tube strength is required. From this point of view, we searched for various components to strengthen the protective tube, and as a result, we came up with ZrO2. In order to significantly exert the effect of reinforcing the protective cylinder of ZrO2, it is necessary to contain at least 0.3%. On the other hand, if it exceeds 6%, although the effect of strengthening the protective cylinder increases, the fluidity of the slag increases. However, defects occur due to slag entrainment. The coating material raw materials 1 to 7 above are:
It is kneaded with a binder such as water glass and applied to the outer periphery of the core wire.

After considering other factors that affect the strength of the circumferential protection tube, we found that the ratio expressed by coating diameter/core wire diameter (hereinafter referred to as coating diameter ratio) was set in the range of 1.35 to 1.65. I learned that even more appropriate protection tube strength can be obtained by doing this. However, if the covering diameter ratio is less than 1.35, the protective tube becomes thin and its strength becomes insufficient, and the welding rod is likely to cause a short circuit during welding. On the other hand, if it exceeds 1.65, the arc voltage becomes high and the welding heat input increases, causing burn-through of the base metal or increasing the amount of slag, which is not preferable. By the way, Figure 2 shows the Zr content in the coating material.
This is a graph showing the results of investigating the influence of O2 amount and coating diameter ratio on the strength of the protective tube (experimental conditions are as below).
2 amount is 0.3 to 6 (Fb and coating diameter ratio is 1.35 to 1
．． By adjusting it within the range of 65, it is possible to reliably obtain an appropriate protection cylinder strength.

[Experimental conditions]

Test rod: 4mmφ Welded joint: plate thickness 3.2m 7x0T joint Welding current: 165A Welding method: Vertical downward contact welding Circles ○, △, and × in Figure 2 have the following meanings.

○: Protective tube is strong, no welding defects △: Protective tube is strong, but there are welding defects (slag entrainment, base metal burn-through)
): 5 to 18 This ratio is an essential requirement to ensure vertical downward welding workability, which is a feature of titania-based welding rods, and to improve the cracking resistance of weld metal.

The individual functions of TlO2, ZrO2, CacO3, and MgCO3 are as explained above, but the inventors further discovered that (TlO2+ZrO2)/(CaCO3+MgC
When the influence of the ratio of O3) on the cracking resistance and remaining bar length of weld metal was investigated, the results shown in Figure 3 were obtained. However, the remaining rod length refers to the length of the unused portion when vertical downward welding is performed using each test rod and welding becomes impossible due to slag entrainment. Since the remaining rod length becomes longer, it can be considered as one evaluation criterion for the performance of the welding rod and welding workability. In addition, the cracking resistance is JI
Measured by S-Z-3155 "C-shaped jig restraint butt weld cracking test method". As a result, regarding the cracking resistance, (TiO2+ZrO2)/(CaCO3+MgCO3
) tends to be better when the value is smaller. However, if this ratio becomes too small, the viscosity of the slag will decrease,
As a result of the entrainment of slag during welding, welding has to be interrupted and the length of the remaining rod becomes longer, which is uneconomical and the advantages of titania-based welding rods cannot be utilized. On the other hand, (T
The above-mentioned items can be satisfied by setting the blending amount of each component so that the ratio of iO2+ZrO2)/(CaCO3+MgCO3) is in the range of 5 to 18. The present invention is roughly constructed as described above, but the key point is that the types and blending ratios of the ingredients are set within specific ranges, and (TlO
By using a coating material with a weight ratio of 2+ZrO2)/(CaCO3+MgCO3) set within a specific range,
While maintaining vertical downward welding workability, which is a feature of titania-based welding rods, it has been possible to significantly improve the cracking resistance of the weld metal. As a result, titania-based welding rods, which were previously only applicable to welding thin plates due to their crack resistance, can now be applied to vertical downward welding of thick plates. It has now become possible to expand the Next, an experimental example will be shown.

Experimental example 1 A coating material with the composition shown in Table 1 was applied to a 4mmφ×400Um
The coating diameter after drying is 6 mmφ (
A titania-based coated arc welding rod was obtained by applying the coating so that the coating diameter ratio was -1.50.

Using each of the obtained welding rods, welding workability was observed by vertical downward welding, and the remaining rod length at the time when welding became impossible was measured. In addition, the cracking test is JIS-Z-31.
The test was carried out in accordance with 55 "C-type jig restraint butt weld cracking test method". The results are summarized in Table 1. From Table 1, it can be considered as follows.

(1) Test rods A-1, 2, and 3 are examples of conventional titania-based coated arc welding rods, and although the content of each coating component is within the preferred range, (TlO2 + ZrO2)
/(CaCO3+MgCO3) is outside the scope of the present invention, so A-1 and 2 have poor cracking resistance, and A-3
In this case, the remaining rod length is long and the workability of vertical downward welding is extremely poor. (
2) C-1 to C-7 are all comparative examples, and (TlO2+Zr
Since the value of O2)/(CaCO3+MgCO3) is within the appropriate range, the remaining rod length is short and the weld metal has good cracking resistance, but the content of one or more of the coating components is Since it does not fall within the range specified by , vertical downward welding workability is poor and the features of titania-based welding rods cannot be demonstrated.

(3) B-1 to B-8 are all examples that satisfy the requirements of the present invention, and the remaining bar length is short and vertical downward welding workability is good, and the resulting weld metal has excellent cracking resistance. ing.

[Brief explanation of drawings]

Figures 1A and b are schematic diagrams comparing the differences in bead shape with and without contact welding in vertical downward welding, and Figure 2 shows the ZrO2 content and coating diameter ratio and the welding rod. The graph shown in Figure 3 showing the relationship between the strength of the protective cylinder is (TiO
2+ZrO2)/(CaCO3+MgCO3) ratio, remaining bar length, and cracking rate.

Claims (1)

[Claims] 1 TiO_2: 35-57%, SiO_2: 15-2
8%, Al_2O_3: 3-8%, Mn: 2.5-9%
, MgCO_3 and/or CaCO_3: 3-10
%, organic matter: 1-8%, ZrO_2: 0.3-6%, and (TiO_2+ZrO_2)/(CaC
The weight ratio given by O_3 + MgCO_3) is 5 to 18
1. A coated arc welding rod, characterized in that a coating agent falling within the range of 100 to 100% is applied to the outer periphery of a mild steel core wire.