KR820000319B1 - Low-hydrogen arc welding electrod - Google Patents

Abstract

This invention relates to low hydrogen arc welding electrode which is high welding material. Dry mix ingredients of flux comprising CaCO315-30 %, CaF220-35 % and Tio2 1-5% make the property of slags and the mechanical property of welded metal in particular impact value at a low temp. Soluble silicate of flux enables the productivity of welding electrode to increase.

Description

High-strength iron-hydrogen-coated arc welding rod

1 is a graph showing the relationship between the components of the fixing agent and the productivity of the electrode.

2 is a diagram showing the slag state according to the TiO 2 change in the coating component.

3 is a graph showing the change of the Charpy impact value according to the impact test temperature.

The present invention relates to a high-strength iron low-hydrogen-based coated arc welding rod (corresponding to American Welding Association standard E7018), which is a high quality welding material.

Conventionally, high strength steel welded structures, such as ship vessels, pressure vessels, nuclear reactors, and gas tanks, which require high safety, have excellent mechanical properties and create perfect welds without various defects. Iron low-hydrogen electrode with welding characteristics has been highly recommended.

However, the iron low hydrogen welding rods developed to date have poor welding efficiency, toughness, which is the most important mechanical property of the weld metal, and poor workability of the weld rod, resulting in poorly shaped weld beads. Many defects appear, such as welding defects such as undercuts. In other words, the arc is shaken or unstable during the welding, the concentration tends to be weak, and spatters are generated. Therefore, the welding efficiency is deteriorated, the quality of the weld is greatly degraded, and the molten slag viscosity ), It is not suitable to protect the weld metal, and it is not easy to remove it after solidification. Therefore, it is necessary to improve such a problem in order to increase the reliability of the welded part.

In particular, the above-mentioned defects are more prominent in the welding posture such as the top view and the vertical, deteriorating the quality of the welded portion, which is a decisive factor, making the effective and efficient welding difficult.

The present invention aims to improve the various problems in welding described above, localize excellent welding materials with excellent mechanical properties of welded metal and improve welding efficiency as domestic techniques, strengthen international competitiveness, and further increase exports. This is a new iron low hydrogen electrode.

The present invention has developed different characteristics from the conventional electrode by developing dry powder ingredients and solid Silicate of the flux. In summary, the powder ingredients are CaCO ₃ 15-30%, CaF ₂ 20-5% together with 1-5% TiO ₂ to improve slag properties and improve the mechanical properties of the deposited metal, especially at low temperatures, and the adhesion component of K ₂ O / Na ₂ O ratio Using a mixed solution of K ₂ SiO ₃ and Na ₂ SiO ₃ with 0.5-3.5 as K ₂ O 0.5-3.5% Na ₂ O 0.5-2.0% with the above powder composition, the arc is stabilized and the slag is improved and the welding rod The productivity was greatly improved.

Detailed description of the invention is as follows.

Unlike other types of electrodes, hydrogen should be generated little by little when welding with low-hydrogen electrodes. For this purpose, CaCO ₃ and CaF ₂ can be used as the main components, but in this case, the basicity is rapidly increased. Due to this greatly reduces the safety of the arc, it is necessary to select the optimum blending range in which the functions of these components are maximized when the coating material is manufactured.

Accordingly, in the present invention, the optimum addition amount of CaC0 ₃ was first found to be optimally in the range of 15 to 30%. At 15% or less, the viscosity of the slag is reduced, so that the flow of the slag is faster, and it is very bad for the vertical welding and the upper welding. welding (Fillet welding) in the slag of the deposited metal to he flows ahead of the arc undercuts (undercut) is caused to be less protective gas the amount of CO ₂ the molten metal does not block air and complete oxygen and nitrogen readily incorporated Mechanical properties are greatly reduced. When the CaCO ₃ is more than 30%, the viscosity of the slag is greatly increased, and sufficient chemical reaction does not occur between the slag and the molten metal, so that the molten metal is not completely refined, and the slag does not solidify uniformly. As a result, the surface of the beads is uneven and irregularities appear, resulting in uneven beads.

CaF ₂ was added to adjust the slag melting point and flowability. This function of CaF ₂ is closely related to CaCO ₃ . In the range of 40-60% of the combined amount of CaCO ₃ and CaF ₂ , the optimum amount of CaF ₂ was 20-35%. If CaF ₂ is less than 20%, the slag fluidity decreases and the slag becomes too close to the Weld Puddle, which prevents the continuous generation of the arc, causing the arc to become unstable and frequently short-circuited, while simultaneously causing a large amount of spatter ( Spatter) and the appearance of the weld bead becomes very poor. In addition, the molten slag does not completely cover the molten metal, so that the so-called slag discontinuity (Island Type Covering) phenomenon, in which a part of the welding bead is exposed, greatly reduces the performance of the weld metal.

When CaF ₂ exceeds 35%, the slag viscosity is greatly lost and the arc cannot easily follow the progress of the arc. As a result, the slag loses the function of covering and protecting the molten metal, thereby deteriorating the mechanical properties of the deposited metal.

TiO ₂ stabilizes the arc in the range of 1-5%, increases the viscosity of the slag to completely cover the bead, and makes the beads beautiful, but at 1% below, the arc becomes unstable, the surface tension of the slag becomes large, and the slag completely deposits the deposited metal. It can't be covered, so exposed parts appear and undercut increases.

When the TiO ₂ is more than 5%, the viscosity of the slag is greatly reduced, which makes it difficult to handle the slag during welding, uneven appearance of the weld bead, and poor shape. The fixation component is a mixed solution of K ₂ SiO ₃ and Na ₂ SiO, and the K ₂ O / Na ₂ O ratio is 0.5-3.5, K ₂ O 0.5-3.5%, N ₂ O 0.5-2.0% When used for replication, the arc was improved and the productivity of the weld was increased. First, if the K ₂ O / Na ₂ O ratio is less than 0.5, the wet-mixing condition of the coating is poor and the extrudability during welding of the welding rod causes the welding rod manufacturing speed. The formability decreases, the coating deforms due to the deterioration of the formability, and after drying, the uniformity appears, which greatly reduces the value of the electrode.

If the ratio exceeds 3.5, the conductive coating of the dried coating is increased, so that the welding rod is not preheated by the heat of resistance in the coating itself during welding. Below 0.5% K ₂ O, the arc becomes unstable and spatters increase, and above 3.5 the slag viscosity decreases. If the Na ₂ O is less than 0.5%, the welding speed decreases, and the welding efficiency is lowered. If the slag solidification speed is lowered above 1.5%, the molten slag solidifies quickly.

Fe improves welding efficiency, stabilizes the arc by minimizing melt droplets, and 15-35% is in an appropriate range. Below 15%, Fe cannot achieve high welding efficiency for the purpose of iron-hydrogen system. It is thick and not suitable for vertical welding and top welding position.

In addition, in the present invention, the slag generating agent used SiO ₂ 8-13%, Si 2.0-5.0, Mn 2.0-3.0% as the deoxidizer to improve the viscosity and removal properties of the slag, to improve the stability of the arc and to the molten metal The dissolved oxygen was removed to increase the mechanical properties of the deposited metal, reduce porosity and cracking, and increase the fatigue strength and impact value at low temperatures. In addition, sodium alginate and 0.5-3.0% of wood powder were added as other components to improve extrudability and arc stability when manufacturing welding rods, and small amounts of impurities such as MgO and Al ₂ O ₃ (1.0-) 4.0%).

Next, the implementation of the present invention will be described.

[Table 1] Compounding ingredients of the coating agent (wt%)

Table 1 shows the representative basic compounding components of the present invention, and five kinds of coating materials were manufactured and mechanically imaged to a thickness of 7.1 mm on a mild steel core having a diameter of 4 mm, in which the ratio of K ₂ O / Na ₂ O was used. According to the results of the measurement on the extrudability and formability of the electrode according to the first degree.

According to the results, the production rate was 500-550 per minute in the K ₂ O / Na ₂ O ratio range of 0.5-3.5 and the incidence of defective products was low as 0-0.5%. When the K ₂ O / Na ₂ O ratio was smaller than 0.5 or larger than 3.5, the extrudability and formability of the electrode showed a tendency to decrease. The test of the workability of the welding rod was measured by welding the mild steel with the thickness of 19mm as the welding base material according to the welding conditions specified in Table 2.

Example 1 showed that when an appropriate amount of CaCO ₃ was blended, the arc became very stable and the appearance of the weld beads was clean. In Example 2, the main components of the coating were properly added, so that the arc and weld bead conditions were good, in particular, the slag fluidity was good and it was easily removed after solidification.

Example 3 shows the effect of TiO ₂ on the slag. When 20 cm of TiO ₂ was welded at 1-5% as in the second degree, the weld metal was completely covered with the slag and shielded from the atmosphere. And if Na ₂ O is appropriate, the penetration was deep even though the welding speed is increased. In Example 4, CaF ₂ was abundant, and thus the slag following state of the slag during welding was very good. And if K ₂ O is proper, the arc becomes stable. Example 5 showed good results as in Example 2.

The analysis results of chemical composition of the weld metal are shown in Table 3. All 5 species are composed of fine acicular ferrite structure that improves the mechanical properties because the Mn amount is higher than that of the base material and core wire. There were no crack-like defects.

Next, the results of mechanical properties are shown in Table 4, and both tensile strength and yield point are superior to the base metal, and the impact value is very good, especially the toughness at low temperature.

[Table 2] Welding Conditions

[Table 3] Chemical Composition of Welded Metal, Wool, Core Wire (Weight%)

[Table 4] Mechanical Properties of Welded Metals

Claims (1)

CaCo ₃ 15-30%, CaF ₂ 20-35% of the total coating material, the amount of the two components is 40-60%, CiO ₂ 8-13%, TiO ₂ 1-5%, Fe 15-35%, other deoxidizers, arc stabilizers, and slag generated by the combined first coating agent (Flux) a powder component and a K ₂ O / Na ₂ O ratio of the fixing agent containing K ₂ SiO ₃ and Na ₂ SiO ₃ in the range from 0.5 to 3.5 High strength steel iron-hydrogen-based coated arc welding rod manufactured by mixing K ₂ O 0.5-3.5% and Na ₂ O 0.5-2.0% with respect to the whole coating. ).

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