High-toughness welding rod for backing welding as well as preparation method and application of high-toughness welding rod

Abstract

The invention belongs to the technical field of welding materials, and particularly provides a high-toughness welding rod for backing welding, the high-toughness welding rod for backing welding comprises a core wire and a coating wrapping the core wire, and the coating comprises, by weight, 40-46% of CaCO3, 20-25% of CaF2, 5-8% of TiO2, 8-12% of SiO2, 7-9% of Si-Fe, 4-7% of Mn, 1-3% of CeO2, 0.5-1% of Ni and the balance iron powder. The high-toughness welding rod for backing welding is a high-toughness basic welding rod with a low-hydrogen potassium-sodium coating, welding spatter is small, forming is attractive, deslagging is easy, all-position welding can be conducted, single-face welding and double-face forming can be achieved during backing welding of a welded pipeline, the diffusible hydrogen content is low, and the welding state and heat treatment state performance is excellent; and the impact energy at the low temperature of-50 DEG C can be ensured to be more than 100J. A diffusible hydrogen mercury method test result [H] of deposited metal is less than or equal to 5mL / 100g, and the index requirement of ultra-low hydrogen is met. The method is suitable for 50Kg-level maritime work matched backing welding, and can be used for backing welding, repairing and the like of pipeline steel and alloy steel.

Description

Technical Field

[0001] This invention belongs to the field of welding materials technology, specifically relating to a high-toughness welding electrode for root pass welding, its preparation method, and its application. Background Technology

[0002] With the continuous development of the marine engineering field, the types of welding materials required by the marine engineering industry are becoming increasingly diverse, and the performance requirements for welding materials are also becoming increasingly stringent. Extreme environmental conditions and severe service conditions demand that welding materials possess higher mechanical properties and excellent processability. Since the interior of pipes cannot be ground or otherwise treated after welding, the root pass welding must achieve the goal of good front-side welding and good back-side forming. Summary of the Invention

[0003] The purpose of this invention is to provide a welding material that meets the requirements of extreme environmental conditions and severe service conditions in the marine engineering industry.

[0004] Therefore, the present invention provides a high-toughness welding electrode for root pass welding, comprising a core and a coating wrapped around the core. By weight percentage, the coating comprises: 40-46% CaCO3, 20-25% CaF2, 5-8% TiO2, 8-12% SiO2, 7-9% Si-Fe, 4-7% Mn, 1-3% CeO2, 0.5-1% Ni, and the remainder being iron powder.

[0005] Specifically, by weight percentage, the coating comprises: 40% CaCO3, 25% CaF2, 5% TiO2, 8% SiO2, 7% Si-Fe, 4% Mn, 1% CeO2, 0.5% Ni, and 9.5% iron powder.

[0006] Specifically, by weight percentage, the coating comprises: 46% CaCO3, 20% CaF2, 5% TiO2, 9% SiO2, 7% Si-Fe, 6% Mn, 2% CeO2, 1% Ni, and 4% iron powder.

[0007] Specifically, by weight percentage, the coating comprises: 42% CaCO3, 23% CaF2, 8% TiO2, 12% SiO2, 7% Si-Fe, 5% Mn, 1.5% CeO2, 0.7% Ni, and 0.8% iron powder.

[0008] Specifically, by weight percentage, the coating comprises: 41% CaCO3, 22% CaF2, 6% TiO2, 10% SiO2, 9% Si-Fe, 7% Mn, 3% CeO2, 0.8% Ni, and 1.2% iron powder.

[0009] Specifically, by weight percentage, the coating comprises: 42% CaCO3, 21% CaF2, 7% TiO2, 11% SiO2, 8% Si-Fe, 4% Mn, 1% CeO2, 0.5% Ni, and 5.5% iron powder.

[0010] Specifically, the aforementioned coating accounts for 30-35% of the total weight of the welding electrode.

[0011] Specifically, the aforementioned welding core is H08GX steel wire.

[0012] The present invention also provides a method for preparing the above-mentioned high-toughness welding electrode for root pass welding, comprising the following steps: stirring and mixing the flux powder evenly; adding a binder to the evenly mixed powder and stirring, then coating it onto the welding core to form a high-toughness welding electrode.

[0013] Specifically, the binder mentioned above is potassium sodium silicate.

[0014] This invention also provides the application of the above-mentioned high-toughness welding electrode for root pass welding in the root pass welding and repair of 50Kg marine engineering products.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0016] The high-toughness welding electrode for root pass welding provided by this invention is a high-toughness alkaline electrode with a low-hydrogen potassium-sodium coating. It exhibits minimal spatter, aesthetically pleasing weld formation, easy slag removal, and the ability to perform all-position welding. When performing root pass welding on pipelines, it can achieve single-sided welding with double-sided forming. It has a low diffusible hydrogen content and excellent performance in both the as-welded and heat-treated states. Its impact energy at -50℃ can be guaranteed to be above 100J. The mercury method test result for the diffusible hydrogen in the deposited metal is ≤5mL / 100g, meeting the requirements for ultra-low hydrogen. It is suitable for 50kg-class marine engineering root pass welding and can be used for root pass welding and repair of pipeline steel and alloy steel. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Although representative embodiments of the present invention have been described in detail, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be defined by the appended claims and their equivalents.

[0018] This invention provides a high-toughness welding electrode for root pass welding, comprising a core and a coating surrounding the core. By weight percentage, the coating comprises: 40-46% CaCO3, 20-25% CaF2, 5-8% TiO2, 8-12% SiO2, 7-9% Si-Fe, 4-7% Mn, 1-3% CeO2, 0.5-1% Ni, with the remainder being iron powder. Optionally, the coating accounts for 30-35% of the total weight of the electrode; the core is preferably H08GX steel wire.

[0019] CaCO3 is mainly added in the form of marble, primarily for slag formation, gasification, and desulfurization. During the root pass welding, the arc blowing force is increased to allow the molten iron to penetrate to the back of the workpiece. When the carbonate content is low, the arc blowing force is insufficient, and the effect of single-sided and double-sided forming cannot be achieved. When the carbonate content is too high, there is a lot of slag, the fluidity of the molten iron is poor, and the weld formation is inadequate. The total amount of CaCO3 should be controlled between 40% and 46%.

[0020] CaF2 is mainly added in the form of fluorite, acting as a thinner slag, improving the fluidity of molten iron, and reducing the content of diffusible hydrogen. Low fluoride content results in poor weld formation and insignificant hydrogen removal, while excessively high fluoride content leads to poor arc stability. Its total amount should be controlled between 20% and 25%.

[0021] TiO2 is mainly added in combination with one or more of rutile, reduced titanium, and titanium dioxide. The addition of TiO2 can improve slag removal performance, refine molten droplets, and make the weld bead dense. However, excessive use can easily reduce mechanical properties. Its total amount should be controlled at 5-8%.

[0022] SiO2 is mainly added in combination with one or more of quartz, silica powder, and feldspar. SiO2 can increase the fluidity of molten iron, making the molten iron flow well in narrow gap bevels. However, excessive use will increase splashing and slag adhesion, so its content is controlled at 8-12%.

[0023] Si-Fe is mainly added in the form of atomized ferrosilicon. It is a deoxidizer that can improve the strength of the cladding metal and increase the fluidity of the molten iron. However, when the ferrosilicon content is too high, it will lead to excessive strength and reduced impact toughness. Therefore, its content is controlled at 7-9%.

[0024] Manganese is mainly added in one or a combination of electrolytic manganese, metallic manganese, and ferrosilicon manganese alloys, primarily as a deoxidizer. It can improve the strength of the deposited metal, its low-temperature impact resistance, and its desulfurization effect. However, when the content is too high, the strength is too high but the impact resistance is poor; when the content is too low, the deoxidation is insufficient and the low-temperature impact resistance is reduced. Therefore, its content is controlled between 4% and 7%.

[0025] Ni is mainly added in the form of nickel powder, which can improve low-temperature impact toughness. However, when the content is too low, the effect of improving low-temperature impact is not obvious. When the content is too high, due to its low melting point, the back side is poorly formed when single-sided welding and double-sided forming. Therefore, its content is controlled between 0.5% and 1%.

[0026] CeO2 is a rare earth oxide that can refine grains and improve low-temperature impact toughness. When the content is too high, the viscosity of the slag increases, making slag removal difficult; when the content is too low, the effect of improving impact toughness is not obvious. Therefore, its content is controlled between 1% and 3%.

[0027] In one embodiment, the coating comprises, by weight percentage: 40% CaCO3, 25% CaF2, 5% TiO2, 8% SiO2, 7% Si-Fe, 4% Mn, 1% CeO2, 0.5% Ni, and 9.5% iron powder.

[0028] In another embodiment, the coating comprises, by weight percentage: 46% CaCO3, 20% CaF2, 5% TiO2, 9% SiO2, 7% Si-Fe, 6% Mn, 2% CeO2, 1% Ni, and 4% iron powder.

[0029] In another embodiment, the coating comprises, by weight percentage: 42% CaCO3, 23% CaF2, 8% TiO2, 12% SiO2, 7% Si-Fe, 5% Mn, 1.5% CeO2, 0.7% Ni, and 0.8% iron powder.

[0030] In another embodiment, the coating comprises, by weight percentage: 41% CaCO3, 22% CaF2, 6% TiO2, 10% SiO2, 9% Si-Fe, 7% Mn, 3% CeO2, 0.8% Ni, and 1.2% iron powder.

[0031] In another embodiment, the coating comprises, by weight percentage: 42% CaCO3, 21% CaF2, 7% TiO2, 11% SiO2, 8% Si-Fe, 4% Mn, 1% CeO2, 0.5% Ni, and 5.5% iron powder.

[0032] The present invention also provides a method for preparing the above-mentioned high-toughness welding electrode for root pass welding, comprising the following steps: stirring and mixing the flux powder evenly; adding a binder to the evenly mixed powder and stirring, then coating it onto the welding core to form a high-toughness welding electrode.

[0033] Specifically, the binder is potassium sodium silicate, preferably high-modulus potassium sodium silicate with a modulus of 3.2.

[0034] This invention also provides the application of the above-mentioned high-toughness welding electrode for root pass welding in the root pass welding and repair of 50Kg marine engineering products.

[0035] The following specific embodiments illustrate the effects of the high-toughness welding electrode for root pass welding of the present invention, its preparation method, and its application.

[0036] Example 1:

[0037] This embodiment provides a high-toughness welding electrode for root pass welding, including a core and a coating wrapped around the core. The coating accounts for 35% of the total weight of the electrode. By weight percentage, the coating includes: CaCO3: 40%, CaF2: 25%, TiO2: 5%, SiO2: 8%, Si-Fe: 7%, Mn: 4%, CeO2: 1%, Ni: 0.5%, and iron powder: 9.5%.

[0038] Using existing welding electrode production equipment and processes, the flux powder is stirred and mixed evenly; potassium sodium water glass is added to the evenly mixed powder and stirred, then coated onto the welding core to produce a high-toughness welding electrode.

[0039] Example 2:

[0040] This embodiment provides a high-toughness welding electrode for root pass welding, including a core and a coating wrapped around the core. The coating accounts for 35% of the total weight of the electrode. By weight percentage, the coating includes: CaCO3: 46%, CaF2: 20%, TiO2: 5%, SiO2: 9%, Si-Fe: 7%, Mn: 6%, CeO2: 2%, Ni: 1%, and iron powder: 4%.

[0041] Using existing welding electrode production equipment and processes, the flux powder is stirred and mixed evenly; potassium sodium water glass is added to the evenly mixed powder and stirred, then coated onto the welding core to produce a high-toughness welding electrode.

[0042] Example 3:

[0043] This embodiment provides a high-toughness welding electrode for root pass welding, including a core and a coating wrapped around the core. The coating accounts for 35% of the total weight of the electrode. By weight percentage, the coating includes: CaCO3: 42%, CaF2: 23%, TiO2: 8%, SiO2: 12%, Si-Fe: 7%, Mn: 5%, CeO2: 1.5%, Ni: 0.7%, and iron powder: 0.8%.

[0044] Using existing welding electrode production equipment and processes, the flux powder is stirred and mixed evenly; potassium sodium water glass is added to the evenly mixed powder and stirred, then coated onto the welding core to produce a high-toughness welding electrode.

[0045] Example 4:

[0046] This embodiment provides a high-toughness welding electrode for root pass welding, including a core and a coating wrapped around the core. The coating accounts for 35% of the total weight of the electrode. By weight percentage, the coating includes: CaCO3: 41%, CaF2: 22%, TiO2: 6%, SiO2: 10%, Si-Fe: 9%, Mn: 7%, CeO2: 3%, Ni: 0.8%, and iron powder: 1.2%.

[0047] Using existing welding electrode production equipment and processes, the flux powder is stirred and mixed evenly; potassium sodium water glass is added to the evenly mixed powder and stirred, then coated onto the welding core to produce a high-toughness welding electrode.

[0048] Example 5:

[0049] This embodiment provides a high-toughness welding electrode for root pass welding, including a core and a coating wrapped around the core. The coating accounts for 35% of the total weight of the electrode. By weight percentage, the coating includes: CaCO3: 42%, CaF2: 21%, TiO2: 7%, SiO2: 11%, Si-Fe: 8%, Mn: 4%, CeO2: 1%, Ni: 0.5%, and iron powder: 5.5%.

[0050] Using existing welding electrode production equipment and processes, the flux powder is stirred and mixed evenly; potassium sodium water glass is added to the evenly mixed powder and stirred, then coated onto the welding core to produce a high-toughness welding electrode.

[0051] Example 6:

[0052] The chemical composition, mechanical properties, and hydrogen diffusion properties of the high-toughness welding electrodes prepared in Examples 1-5 were tested according to standard requirements and industry-standard methods. The test results are shown in Tables 1-4.

[0053] Table 1 Chemical composition of deposited metal

[0054]

[0055] Table 2 Mechanical properties of welded metal in the weld state

[0056]

[0057] Table 3 Mechanical properties of the heat-treated weld metal (620℃*3h)

[0058]

[0059] Table 4. Diffusion hydrogen content of deposited metal (mercury method)

[0060]

[0061] As shown in Tables 1-4, the high-toughness welding electrode for root pass welding provided by this invention exhibits minimal spatter, aesthetically pleasing weld formation, easy slag removal, and the ability to perform all-position welding. When performing root pass welding on pipelines, it can achieve single-sided welding with double-sided forming. It has low diffusible hydrogen content and excellent performance in both the weld and heat-treated states, maintaining an impact energy above 100J at -50℃. The mercury method test result for diffusible hydrogen in the deposited metal shows [H] ≤ 5mL / 100g, meeting the requirements for ultra-low hydrogen content. It is compatible with 50kg-grade marine engineering root pass welding electrodes and can be used for root pass welding and repair of pipeline steel and alloy steel.

[0062] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A high-toughness welding electrode for root pass welding, comprising a core and a flux coating covering the core, characterized in that, By weight percentage, the coating comprises: 40-46% CaCO3, 20-25% CaF2, 5-8% TiO2, 8-12% SiO2, 7-9% Si-Fe, 4-7% Mn, 1-3% CeO2, 0.5-1% Ni, with the remainder being iron powder.

2. The high-toughness welding electrode for root pass welding as described in claim 1, characterized in that: The coating comprises, by weight percentage: 40% CaCO3, 25% CaF2, 5% TiO2, 8% SiO2, 7% Si-Fe, 4% Mn, 1% CeO2, 0.5% Ni, and 9.5% iron powder.

3. The high-toughness welding electrode for root pass welding as described in claim 1, characterized in that: The coating comprises, by weight percentage: 46% CaCO3, 20% CaF2, 5% TiO2, 9% SiO2, 7% Si-Fe, 6% Mn, 2% CeO2, 1% Ni, and 4% iron powder.

4. The high-toughness welding electrode for root pass welding as described in claim 1, characterized in that: The coating comprises, by weight percentage: 42% CaCO3, 23% CaF2, 8% TiO2, 12% SiO2, 7% Si-Fe, 5% Mn, 1.5% CeO2, 0.7% Ni, and 0.8% iron powder.

5. The high-toughness welding electrode for root pass welding as described in claim 1, characterized in that: The coating comprises, by weight percentage: 41% CaCO3, 22% CaF2, 6% TiO2, 10% SiO2, 9% Si-Fe, 7% Mn, 3% CeO2, 0.8% Ni, and 1.2% iron powder.

6. The high-toughness welding electrode for root pass welding as described in claim 1, characterized in that: The coating comprises, by weight percentage: 42% CaCO3, 21% CaF2, 7% TiO2, 11% SiO2, 8% Si-Fe, 4% Mn, 1% CeO2, 0.5% Ni, and 5.5% iron powder.

7. The high-toughness welding electrode for root pass welding as described in claim 1, characterized in that: The coating comprises 30-35% of the total weight of the welding electrode.

8. The high-toughness welding electrode for root pass welding as described in claim 1, characterized in that: The welding core is H08GX steel wire.

9. The method for preparing the high-toughness welding electrode for root pass welding as described in any one of claims 1-8, characterized in that, Includes the following steps: Stir and mix the flux powder evenly; add binder to the evenly mixed powder and stir, then coat it onto the welding core to make a high-toughness welding rod.

10. The application of the high-toughness welding electrode for root pass welding as described in any one of claims 1-8 in the root pass welding and repair of 50Kg marine engineering products.

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