JP2019115913A - Lime-titania type covered electrode - Google Patents

Abstract

To provide a lime-titania type covered electrode excellent in various performances including a welding workability and the like, particularly excellent in slag peelability even in welding of a thin steel sheet.SOLUTION: A lime-titania type covered electrode in which a coating material is coated on a steel core wire is characterized by including in mass% based on total mass of coating material, 8-18% sum of metal carbonate, 10-25% total of TiOconversion value, 10-25% total of SiOconversion value, 1-5% total of AlOconversion value, 2-6% total of organic materials, more than 1.50-4.55% CaO, 1-5% MgO, 2-8% Mn, 0.03-0.50% Ti, 20-40% iron dust, 0.01-0.05% iron sulfide, 0.5-3.5% total of NaO and KO conversion values, and the balance comprising the coating material, Fe content from iron alloy and inevitable impurities.SELECTED DRAWING: None

Description

  The present invention relates to a lime-titanium-based coated arc welding rod suitable for securing various performances such as welding workability and improving slag removability particularly in welding of thin steel plates.

  Non-low hydrogen-based coated arc welding rods are often used for welding of mild steel and 490 MPa grade high-tensile steels because they have excellent welding workability as compared with various coated arc welding rods. Among them, lime-titanian coated arc welding rods are widely used in general structures such as vehicles and buildings because they have a good bead appearance, a small amount of spatter and a good re-arcing property.

  However, when welding lap joints and T-joints of thin steel plates with a thickness of 1.2 to 6 mm with a lime-titanium-based coated arc welding rod, the slag removability becomes poor and the welding work efficiency deteriorates. There is a problem of that.

  Therefore, various proposals have been made so far to improve the slag removability of non-low hydrogen-based coated arc welding rods. For example, Patent Document 1 stipulates the contents of MgO and water of crystallization in the coating material of lime-titanium-based coated arc welding, and the hydrogen generated from water of crystallization is diffused into the slag while maintaining the viscosity of the slag by MgO. There is disclosed a technique for improving the slag removability by allowing it to be made porous. According to this technology, it is possible to improve the slag removability of the lime-titanian coated arc welding rod, but in the case of welding the lap joint portion and the T joint portion of thin steel plate, the problem is that sufficient slag removability can not be obtained. was there.

Patent Document 2 also discloses a technology for improving the slag removability by suppressing the total amount of iron oxide in the coating of the non-low hydrogen-based coated arc welding rod as much as possible to increase the difference between thermal expansion and contraction of the slag. Is disclosed. Further, Patent Document 3 discloses a technique for improving the slag removability by reducing Nb ₂ O ₅ and V ₂ O _{5 and the} like in a coating material of illuminite-based coated arc welding. However, the techniques disclosed in Patent Documents 2 and 3 have a problem that sufficient slag removability can not be secured in the welding of the lap joint portion and the T joint portion of thin steel plates.

Japanese Patent Application Laid-Open No. 56-71597 Japanese Patent Application Laid-Open No. 6-262391 JP 2004-243351 A

  Therefore, the present invention has been devised in view of the problems described above, and secures various performances such as welding workability, and also slag separation sufficient in welding of lap joints of thin steel plates and T joints. It is an object of the present invention to provide a lime-titanium-based coated arc welding rod capable of securing the properties.

The gist of the present invention is a lime titinia-based coated arc welding rod in which a coating material is coated on a steel core wire, wherein the coating material is one or two or more kinds of metal carbonates in mass% with respect to the total mass of the coating material. Total: 8 to 18%, total of TiO ₂ equivalent value of Ti oxide: 10 to 25%, total of SiO ₂ equivalent value of Si oxide: 10 to 25%, Al ₂ O ₃ equivalent value of Al oxide Total: 1 to 5%, total of one or more organic substances: 2 to 6%, CaO: more than 1.50 to 4.55%, MgO: 1 to 5%, Mn: 2 to 8%, Ti : 0.03 to 0.50%, iron powder: 20 to 40%, iron sulfide: 0.01 to 0.05%, total of Na ₂ O converted value and K ₂ O converted value of Na compound and K compound: It contains 0.5 to 3.5%, and the balance is composed of a coating agent, Fe from iron alloy and unavoidable impurities That is Raimuchitaniya system covered electrode.

  According to the lime-titanium-based coated arc welding rod of the present invention, various performances such as good welding workability can be secured, and the slag removability is excellent particularly in welding of lap joints of thin steel plates and T-joints, It can greatly contribute to the improvement of welding operation efficiency.

  MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the present inventors produced the lime titinia type | system | group coated arc welding rod, and investigated in detail about welding workability, such as slag removability at the time of welding of a thin steel plate. As a result, in welding of thin steel plates, the steel plate heated by the welding heat is difficult to be cooled, so the molten slag which encapsulates the molten pool is not uniformly encapsulated, and the molten slag tends to seize on the bead surface, I found out that the sex would be bad. Therefore, slag separation is performed even during welding of thin steel plates while maintaining the excellent bead shape and appearance, reworkability, arc stability, etc. welding workability and the weld metal mechanical performance, which are the features of the lime-titanian coated arc welding rod. As a result of examining various methods to improve the toughness, the necessary mechanical performance of the weld metal is secured by adding an appropriate amount of Mn and Ti to the coating material, and Ti oxide, Si oxide, Al oxide, CaO, Na By adding a proper amount of compound and K compound, the arc stability is improved and the amount of sputtering is reduced, and by adding a proper amount of Ti oxide, the bead shape and appearance are improved, and by adding a proper amount of organic matter and iron powder. It has been found that welding defects such as blow holes can be prevented by improving the re-arcing property, the burn resistance and the chipping resistance, and adding appropriate amounts of metal carbonate and Mn. On the other hand, regarding the slag removability, the surface tension of the molten slag can be lowered by adding an appropriate amount of Si oxide, MgO and iron sulfide, and the molten slag can be uniformly covered over the entire surface of the molten pool, It has been found that slag seizure can be prevented and sufficient slag removability can be obtained.

  Hereinafter, the component composition of the coating agent of the lime titinia-based coated arc welding rod in the present invention and the reason for limitation of the component composition will be described in detail. In addition, content of each component composition shall be represented by the mass% with respect to the coating agent total mass, and when expressing the mass%, it shall be described only as%.

[Sum of one or more of metal carbonates: 8 to 18%]
Metal carbonate is added from calcium carbonate, magnesium carbonate, barium carbonate, manganese carbonate, lithium carbonate and the like, and has the effect of decomposing in the arc to generate CO ₂ gas and shielding the deposited metal from the atmosphere and protecting it. . If the sum of one or more of the metal carbonates is less than 8%, the shielding effect is insufficient and blow holes are likely to occur. On the other hand, if the sum of one or more of the metal carbonates exceeds 18%, the arc becomes unstable and becomes a convex bead, and the slag removability also deteriorates. Therefore, the sum of one or more of metal carbonates in the coating agent is 8 to 18%.

[Total TiO ₂ converted value of Ti oxide: 10 to 25%]
Ti oxide is added from ruthenium, titanium oxide, sodium titanate, titanium slag, etc., acts as a slag forming agent and an arc stabilizer, and has the effect of improving the arc stability and the bead shape and appearance. When the total of TiO ₂ converted values of Ti oxides is less than 10%, the arc becomes unstable, and the slag fluidity deteriorates, and the bead shape and the appearance become poor. On the other hand, when the total of the TiO ₂ converted value of Ti oxide exceeds 25%, the slag becomes dense and the slag removability becomes poor. Therefore, the total of the TiO ₂ conversion value of Ti oxide in a coating agent shall be 10 to 25%.

[Total of SiO ₂ converted value of Si oxide: 10 to 25%]
Si oxide is added from silica sand, feldspar, water glass and the like, acts as a slag forming agent and an arc stabilizer, and has the effect of improving the arc stability and the slag removability. If the total of the SiO ₂ conversion value of Si oxide is less than 10%, the arc becomes weak and unstable, and the vitreous quality of the formed slag decreases, and the slag removability becomes poor particularly when welding thin steel plates . On the other hand, when the total of the SiO ₂ conversion value of Si oxide exceeds 25%, the viscosity of the slag becomes high and the bead shape becomes defective. Therefore, the total of the SiO ₂ conversion value of Si oxide in a coating agent shall be 10-25%.

[Total of Al ₂ O ₃ converted values of Al oxide: 1 to 5%]
Al oxide is added from alumina, feldspar, silica sand, mica and the like, and has the effect of stabilizing the arc. If the total of Al ₂ O ₃ converted values of Al oxides is less than 1%, the arc is weak and unstable. On the other hand, when the total of the Al ₂ O ₃ conversion value of Al oxide exceeds 5%, the slag removability becomes poor particularly when welding thin steel plates. Therefore, the total of the Al ₂ O ₃ conversion value of Al oxide in the coating agent is 1 to 5%.

[Sum of one or more organic substances: 2 to 6%]
Organic substances are added from cellulose, dextrin, flour, starch, corn starch and the like to improve the re-arcing property and to improve the coating chipping resistance. If the sum of one or more of the organic substances is less than 2%, good re-arcing properties can not be obtained and coating chipping tends to occur. On the other hand, if the sum of one or more of the organic substances exceeds 6%, the arc becomes too strong and the bead shape becomes poor. In addition, the coating material becomes reddish and burns easily. Therefore, the sum of one or more of the organic substances in the coating agent is 2 to 6%.

[CaO: more than 1.50 to 4.55%]
CaO is added from wollastonite, calcium titanate or the like to stabilize the arc and is effective in reducing spatter. When CaO is 1.50% or less, the effect can not be obtained, the arc becomes unstable, and the amount of sputtering increases. On the other hand, if CaO exceeds 4.55%, the arc weakens and becomes unstable, and welding defects such as poor fusion tend to occur. Therefore, CaO in the coating agent is made more than 1.50 to 4.55%.

[MgO: 1 to 5%]
MgO is added from magnesia clinker etc. and has the effect of improving the slag removability. If the content of MgO is less than 1%, the effect can not be obtained, and the slag removability becomes poor particularly when welding thin steel plates. On the other hand, when the content of MgO exceeds 5%, the slag itself becomes hard and the bead shape becomes convex. Therefore, the content of MgO in the coating agent is 1 to 5%.

[Mn: 2 to 8%]
Mn is added from metal Mn, Fe-Mn, Fe-Si-Mn, etc. and added as a deoxidizing agent, and is effective for improving the strength and toughness of the weld metal. If Mn is less than 2%, deoxidation becomes insufficient and blow holes easily occur. In addition, the strength and toughness of the weld metal are reduced. On the other hand, if Mn exceeds 8%, the strength of the weld metal becomes excessively high, and the toughness decreases. Therefore, the Mn in the coating agent is 2 to 8%.

[Ti: 0.03 to 0.50%]
Ti is added from metal Ti, Fe-Ti, etc., is effective as a deoxidizer, and has the function of remaining in the weld metal and refining the microstructure of the weld metal to improve the toughness. If Ti is less than 0.03%, deoxidation is insufficient and the toughness of the weld metal is reduced. On the other hand, when Ti exceeds 0.50%, precipitation of Ti oxide in the weld metal increases, and the toughness of the weld metal decreases. Therefore, Ti in the coating agent is made 0.03 to 0.50%.

[Iron powder: 20 to 40%]
Iron powder has the effect of improving the re-arcing property. If the iron powder content is less than 20%, good re-arcing can not be obtained. On the other hand, if the iron powder exceeds 40%, the covering tube becomes short and the arc becomes unstable, and the electrical conductivity of the covering becomes excessively high and side arcs are easily generated. Therefore, the iron powder in the coating agent is 20 to 40%.

[Iron sulfide: 0.01 to 0.05%]
Iron sulfide lowers the surface tension of the molten slag to improve compatibility with the molten pool, and uniformly encapsulates the molten slag over the entire surface of the molten pool, thereby preventing slagging on the surface of the weld bead and thus removing slag. Have the effect of improving If the amount of iron sulfide is less than 0.01%, the effect can not be obtained, and particularly in welding of thin steel plates, slag seizure occurs on the bead surface, resulting in poor slag removability. On the other hand, when the iron sulfide content exceeds 0.05%, the toughness of the weld metal decreases and high temperature cracking is likely to occur. Therefore, the amount of iron sulfide in the coating agent is 0.01 to 0.05%.

[Sum of Na ₂ O conversion value and K ₂ O conversion value of Na compound and K compound: 0.5 to 3.5%]
Na compounds and K compounds are added from sodium silicate, potassium silicate, potassium feldspar, potassium glass, soda feldspar and the like in water glass, and have the effect of improving the arc stability. If the sum of the Na ₂ O converted value and the K ₂ O converted value of the Na compound and the K compound is less than 0.5%, the arc becomes unstable. On the other hand, if the sum of the Na ₂ O-converted value and the K ₂ O-converted value of the Na compound and the K compound exceeds 3.5%, the re-arcing property becomes poor. Therefore, the sum of the Na ₂ O converted value and the K ₂ O converted value of the Na compound and the K compound in the coating agent is 0.5 to 3.5%.

  In addition, the remaining part of the coating agent of the lime titinia-based coated arc welding rod of the present invention can contain one or more kinds of sodium alginate, mica and the like as a coating agent in total at 6% or less in total. -Fe and unavoidable impurities from iron alloys such as -Si-Mn.

  In addition, it is preferable to use JIS G3523 SWY11 as a mild steel core wire to be used. Furthermore, C in the mild steel core wire is 0.05-0.08% in mass% with respect to the total weight of the mild steel core wire, and in mass% with respect to the total mass of the coated arc welding rod, C in total for the mild steel core wire and the coating material 0.06 to 0.20%, P is preferably 0.010% or less because toughness is reduced. Moreover, it is preferable that the coating rate (Mass% of the coating material with respect to the arc welding rod total mass) to the mild steel core wire of a coating material is 25 to 40%.

  The effects of the present invention will be specifically described by way of examples.

  JIS G 3523 SWY 11 mild steel core wire with a diameter of 3.2 mm and a length of 350 mm (C: 0.06% by mass, Si: 0.01% based on the total weight of the soft steel core wire) of a coating agent of various component compositions shown in Table 1 It coats by coating by mass ratio, Mn: 0.48 mass%, P: 0.009 mass%, S: 0.005 mass%) at a coverage of 36% and then dried and various lime titinia-based coated arc welding rods Was prototyped.

  Using the trial welding rod shown in Table 1, welding workability such as slag removability and mechanical performance were investigated.

  For evaluation of welding workability, a 3.2 mm thick JIS G 3131 SPHC steel plate is assembled in a T-shape, using a small welding machine with a secondary side no-load voltage of 60 V, with a welding current of 100 to 140 A horizontal Meat welding was performed to evaluate arc stability, spatter generation state, slag removability, bead shape and appearance, and the presence or absence of welding defects. The presence or absence of this welding defect investigated the presence or absence of coating chipping, stick burning high temperature crack, and side arc generation.

  Moreover, the re-arcing property made the thing which arc generate | occur | produced immediately after welding for 10 seconds, made it a pass, made the test number 20 pieces, and made the thing which passed 16 of 20 pieces favorable.

  The evaluation of mechanical performance is carried out by using a weld metal test with an AC welder according to JIZ Z3111, using JIS G 3106 SM490A with a thickness of 16 mm, and using tensile test pieces (A2) and impact test pieces (V notch test pieces) The sample was taken and subjected to a tensile test and an impact test.

  Evaluation of the tension test made the tensile strength 400-560 Mpa good. The toughness was evaluated by performing a Charpy impact test at a test temperature of 0 ° C., and the average value of absorbed energy of three repetitions was determined to be 60 J or more.

  The weld defects were evaluated by performing X-ray transmission tests according to JIS Z 3106 on the test bodies after the weld metal test, and investigating the presence or absence of blow holes, poor fusion and the like. The results of these surveys are summarized in Table 2.

  In Tables 1 and 2, welding rod No. 1 to No. 9 is an example of the present invention, welding rod No. 9; 10-No. 18 is a comparative example.

Welding rod No. 1 which is an example of the present invention. 1 to No. 9 is the total of metal carbonates in the coating agent, the total of TiO ₂ converted values of Ti oxides, the total of SiO ₂ converted values of Si oxides, the total of Al ₂ O ₃ converted values of Al oxides, organic substances Since the total sum of CaO, MgO, Mn, Ti, iron powder, iron sulfide, Na compound and K compound in terms of Na ₂ O and K ₂ O is appropriate, the arc is stable and the amount of sputtering is small. , Re-arcing property, slag removability and bead appearance / shape were good. In addition, welding defects such as coating chipping, rod burning, and side arcs did not occur, blow holes, fusion defects, high temperature cracks did not occur, and the tensile strength and absorbed energy of the deposited metal were good, and the results were extremely satisfactory. .

In the comparative example, welding rod No. In the case of No. 10, since the total amount of metal carbonate was small, blow holes were generated in the weld. In addition, since the TiO ₂ conversion value was small, the arc was unstable and the bead appearance and shape were poor. Furthermore, since there was little MgO, slag removability was inferior.

  Welding rod No. In No. 11, since the amount of metal carbonate was large, the arc was unstable, the slag removability was poor, and the bead shape was also convex. In addition, crater cracking occurred because the amount of iron sulfide is large, and the absorbed energy of the deposited metal was also low.

Welding rod No. 12, since the TiO ₂ converted value is large, the slag removability was poor. Moreover, since there was much Ti, the absorbed energy of the deposited metal was low. Furthermore, since there were a lot of iron powder, the arc was unstable and a side arc was generated.

Welding rod No. Since No. 13 had a small SiO ₂ conversion value, the arc was weak and the slag removability was poor. Moreover, since there were many MgO, the bead became convex. Furthermore, the re-arcing property was poor because there was little iron powder.

Welding rod No. No. 14 had a large SiO ₂ conversion value, so the bead shape was poor. In addition, since the content of CaO is large, the arc becomes weak and a fusion failure occurs. Furthermore, since there was little Ti, the absorbed energy of the deposited metal was low.

Welding rod No. In No. 15, the arc was weak since the Al ₂ O ₃ conversion value was small. Moreover, since there were few organic substances, re-arcing was inferior and coating chipping occurred. Furthermore, since there were many Mn, the tensile strength of the deposited metal was high, and the absorbed energy was low.

Welding rod No. 16, since in terms of Al ₂ O ₃ value is large, the slag removability was poor. Moreover, since there were few Mn, the tensile strength and absorbed energy of the deposited metal were low. Furthermore, the arc was unstable because the total of the Na ₂ O converted value and the K ₂ O converted value was small.

Welding rod No. The sample No. 17 contained a large amount of organic matter, so the arc was strong, the bead appearance was poor, and a stick burn occurred. In addition, since the total of the Na ₂ O converted value and the K ₂ O converted value is large, the re-arcing property was also poor.

  Welding rod No. Since No. 18 had few CaO, the arc was unstable and the amount of spatters generated was also large. Moreover, since there were few iron sulfides, slag removability was inferior.

Claims (1)

In a lime-titanium-based coated arc welding rod in which a coating is coated on a steel core wire,
The said coating agent is the mass% with respect to the coating agent total mass,
Total of one or more of metal carbonates: 8 to 18%,
Total of TiO ₂ converted value of Ti oxide: 10 to 25%,
Total of SiO ₂ converted value of Si oxide: 10 to 25%,
Total of Al ₂ O ₃ conversion value of Al oxide: 1 to 5%,
Total of one or more organic substances: 2 to 6%,
CaO: more than 1.50 to 4.55%,
MgO: 1 to 5%,
Mn: 2 to 8%,
Ti: 0.03 to 0.50%,
Iron powder: 20-40%,
Iron sulfide: 0.01 to 0.05%,
The sum of Na ₂ O converted value and K ₂ O converted value of Na compound and K compound: 0.5 to 3.5% is contained,
A lime-titanium-based coated arc welding rod, the balance of which comprises a coating agent, an Fe component from an iron alloy, and an unavoidable impurity.