JPH0364237B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a welding end tab that is applied to the end face of a welded member on a groove line when butt welding opposing welded members. (Prior art and its problems) Conventionally, when the grooves of the welded parts are butted against each other and the grooves are welded, regardless of the length of the welded parts, the upper end surface of the groove line of the welded parts Then, end plates or waste plates, usually called end tabs, made of the same material as the part to be welded are subdivided, and the entire length including these end tabs is welded, and the end tabs are removed as a final finish. Ta. However, such methods require considerable time to attach and remove the end tabs. In other words, for long workpieces, the number of end tabs is not very large, so the time required for preparing, installing, removing, and finishing the end tabs accounts for a relatively small proportion of the total welding work. Since the welding length is short, the welding time at that point is relatively short, but when it comes to large structures that use many short welded parts, there are thousands of welding points. There are also a large number of end tabs, and the time ratio of incidental work such as preparation, attachment, removal, and finishing of the end tabs is large, resulting in a disadvantage that efficiency is extremely low. In addition, when welding high-strength steel, the marks of the end tab and tack bead part harden, creating an arc strike-like defect, which reduces the performance of the welded joint, especially the bending strength and fatigue strength. . By the way, Japanese Patent Publication No. 48-28545 was published for the purpose of shortening welding work time by omitting the labor of preparing, attaching, removing and finishing end tabs, and improving welding performance by eliminating defects such as arc strikes. The publication states that in place of conventional end plates or waste plates that are of the same quality as the parts to be welded, a refractory solid material mainly composed of silica, zirconia, alumina, and magnesia-based metal oxides and with a high thermal conductivity at room temperature is used. A welding end tab has been proposed in which a void of an arbitrary shape is bored in a solid flux with high thermal conductivity of 1.2 to 10.6 Kcal/m・hr・℃. However, since such end tabs are made of refractory metal oxide or a mixture of iron powder, the bead shape formed at the end tab section requires smoothness at the bead end surface where the beads overlap. Molten slag from some welding end tabs may get stuck or burned between the overlapping beads that are chipped or lack smoothness, so gouging and repair welding are required to remove the stuck slag. The disadvantage is that the effect of omitting the installation of the end plate is diminished because a grinder operation is required to improve the appearance of the bead. (Objective of the present invention) The role of the solid flux in conventional tab materials is as a refractory material, and there are few that also have the function of a bead forming layer. Therefore, many of the solid flux compositions are highly refractory compositions with a melting point of 1700° C. or higher, and when welding is performed using this type of tab material, bead conformability is poor and it is difficult to form a good bead. Taking this into consideration, we investigated the properties of solid flux and found that melting the tab material to some extent is better in terms of so-called bead formation properties such as bead uniformity, bead conformability, and surface gloss. Based on this, an end tab for welding with good bead forming properties is provided. (Structure, operation, and effect of the invention) The gist of the present invention is that the refractory solid flux has a composition of SiO ₂ :45 to 70 wt% and Al ₂ O ₃ :15 to 70 wt%.
40 wt%, MgO: in the range of 5 to 30 wt%, and SiO ₂ ,
The end tab for welding is characterized in that the sum of Al ₂ O ₃ and MgO is at least 90 wt%, and the apparent porosity is 5 to 40%. The present invention will be explained in detail below. As shown in FIGS. 1 and 2, welded members 1,
1′ facing each other and using the backing metal 9, prepare the groove 2.
The end tab 3 of the present invention is applied so as to be in contact with the side edge of the groove 2, and the magnets 4, 4',
After tightening the bolt 8 of the support jig consisting of the nut 7, bolt 8, and stopper 6 provided at the center of the leaf spring 5 to press and support the end tab toward the center of the groove 2,
Perform groove welding. In the present invention, the solid flux composition is
_SiO2 : 45-70wt%, _Al2O3 : _15-40wt %,
MgO: The reason why we limited it to 5 to 30 wt% is that this range is
SiO ₂ −Al ₂ O ₃ −MgO system composition with melting point of 1350℃~
This is because experimental results have revealed that this is the lowest temperature range at 1500℃, and that it has both the role of a refractory material and a bead forming layer. In other words, by using a solid flux with a composition within the above range, even in the case of downward or lateral welding with relatively low heat input, the part in contact with the bead partially turns into molten slag, forming a slag layer that protects the bead. A glossy, uniform bead can be obtained. If it is outside the above range, the melting point will be high and the fire resistance will be improved, but the solid flux will hardly be melted and the slag layer will be insufficient, resulting in poor bead fitting or overlapping beads. By the way, when producing a solid flux with the above composition at low cost industrially, if low-quality silica, alumina, magnesite, etc. are mixed with the target composition and subjected to firing reaction, some other components other than the above composition may be contained. Sometimes. however
If SiO ₂ , Al ₂ O ₃ and MgO are within the above range, 10
The above effect is not lost even if impurities of about 50% are contained. Next, the apparent porosity of the solid flux of the tab material of the present invention is limited to 5 to 40%. The apparent porosity here refers to a value measured by the following method. Apparent porosity = W ₃ - _{W 1} / W ₃ - W ₂ × 100 (%) where W ₁ : Dry weight of solid flux (g) W ₂ : Weight of saturated solid flux in water (g) W ₃ : Weight in air of solid flux saturated with water (g) When the apparent porosity of solid flux exceeds 40%, the amount of melted solid flux increases significantly, resulting in excessive beads, undercuts, and sputtering. This is undesirable because it deteriorates workability, such as frequent occurrence of welding conditions and narrowing of the welding condition range. When the apparent porosity is 5% or less, the fire resistance of the tab material improves, but there is almost no melting of the solid flux and no slag layer is formed, resulting in defects such as overlap and deterioration of the bead shape. Therefore, the apparent porosity of the solid flux is 5 to 40%. Next, the effects of the present invention will be explained in more detail using Examples and Comparative Examples. Examples Table 1 shows the composition, welding conditions, and test results of the SiO ₂ -Al ₂ O ₃ -MgO-based prototype tab material. In the same table, No. 1 to No. 7 are examples of the end tab material of the present invention, and No. 8 to No. 20 are comparative examples that do not satisfy the constitutional conditions of the end tab material of the present invention.

【table】

[Table] Examples No. 1 to No. 7 of the end tab material of the present invention
A good bead shape with good surface gloss and no defects such as undercuts or overlaps was obtained. However, when SiO ₂ in No. 8 was below the lower limit, the amount of melted solid flux was somewhat small, resulting in overlapping beads. When SiO ₂ in No. 9 was above the upper limit, the melting amount of the solid flux was small, so the bead conformation was somewhat poor, resulting in overlapping beads. When Al ₂ O ₃ in No. 10 was above the upper limit, the amount of melted solid flux was small, resulting in non-uniform and overlapping beads. When Al ₂ O ₃ in No. 11 was below the lower limit, the arc stability near the open end was somewhat poor, and the bead shape was somewhat poor. No.12
When MgO is below the lower limit, the amount of melted solid flux is small, so the bead does not fit well and becomes an overlapping bead. When MgO in No. 13 was above the upper limit, there was almost no amount of melted solid flux, resulting in non-uniform and overlapping beads. When the apparent porosity of solid flux No. 14 exceeded the upper limit, the amount of melted tab material increased significantly, resulting in excessive beads, undercuts, and spatter. When the apparent porosity of solid flux No. 15 was below the lower limit, there was almost no melting amount of the tab material, resulting in poor bead uniformity and overlapping beads. Furthermore, No. 16 to No. 20 are cases where the solid flux composition or the apparent porosity of the solid flux is extremely outside the limit range of the present invention, and in all cases, the arc near the grooved tip is unstable and the bead shape is poor. It became. As described above, use of the end tab material of the present invention not only improves welding performance, but also eliminates the labor of preparing, attaching, removing, and finishing end tabs, and significantly reduces welding work time.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment using the end tab of the present invention, and FIG. 2 is a side view. 1, 1'; Member to be welded, 2; Groove, 3; End tab, 4, 4'; Magnet, 5; Leaf spring, 6;
Stopper, 7; Nut, 8; Bolt, 9; Backing metal.

Claims (1)

[Claims] 1 Refractory solid flux composition is SiO ₂ 45-70wt
%, _{Al2O3 15-40wt} %, MgO5-30%wt% and the sum of _SiO2 , _Al2O3 and _MgO is at least 90wt%, and the apparent porosity is 5-40%. An end tab for welding characterized by: