Red cracking resistant acidic stainless steel welding rod and preparation method thereof

Abstract

The invention provides an anti-redness and anti-cracking acidic stainless steel electrode and a preparation method thereof.The electrode is mainly composed of a core wire and a coating, the coating comprises dry powder and a binder, and the dry powder comprises, by weight, 30-35 parts of rutile, 5-10 parts of titanium dioxide, 20-30 parts of calcined mica, 5-10 parts of feldspar, 5-10 parts of dolomite and 3-5 parts of iron powder; 10-15 parts of chromium metal, 2-4 parts of manganese metal and 5-9 parts of fluorite; the binder is potassium-sodium water glass modified by a water-based rheological additive. The preparation method of the welding rod is simple, the thermal expansion coefficient of the coating is closer to that of a stainless steel core wire, during welding, on the premise that it is guaranteed that the mechanical strength and acid corrosion resistance of a weld joint completely reach the standard, the problems of redness and cracking of the coating are solved synergistically from the material system level, and better comprehensive cost performance is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of welding materials, and particularly relates to an acid stainless steel electrode resistant to red cracking and a preparation method thereof. BACKGROUND

[0002] Stainless steel welding material is a key material for ensuring the performance of stainless steel structure. With the increasingly wide application of 304 austenitic stainless steel due to its excellent comprehensive cost performance, the demand for its matching welding material in the market also continues to grow. Among them, A102 (E308-16) type acid stainless steel electrode has become one of the largest matching electrodes due to its excellent welding process, such as stable arc, smooth deslagging, and suitability for all-position welding.

[0003] However, this type of electrode has two major defects in long-term practical application: first, the coating of the electrode is prone to "redness" in the latter half of the welding process; second, the coating is prone to cracking and even falling off. These problems directly cause the waste of the electrode and also lead to the interruption of welding operation, which seriously affects the construction efficiency and increases the comprehensive cost. The root cause of these problems lies in the mismatch between the inherent high resistivity and high linear expansion coefficient of the austenitic stainless steel core and the physical properties of the coating material.

[0004] To compensate for the alloy loss during welding, the traditional technical route usually uses a standard welding core with high alloy content, such as a standard 308L welding core with Cr-Ni content of 21-10 type, to ensure the composition and performance of the weld. However, this significantly increases the cost of raw materials, and on the other hand, the higher resistivity and linear expansion coefficient of the welding core may exacerbate the redness and cracking tendency of the coating. At the same time, the formulation design of the coating also faces a balance problem: if the alloying agent or metal powder in the coating is reduced to alleviate "redness", the corrosion resistance of the weld may be compromised; if the mineral toughening component is increased to improve the cracking resistance of the coating, the arc stability may be affected or the cost may be increased. Therefore, under the existing technical system, there is a difficult balance to be achieved between the cost control of the electrode, the process performance such as redness resistance and cracking resistance, and the mechanical and corrosion resistance of the weld metal.

[0005] In summary, there is an urgent need to develop a new type of acid stainless steel electrode resistant to red cracking. The electrode needs to solve the problems of "redness" and "cracking" of the coating from the material system level on the premise of ensuring the mechanical strength and acid corrosion resistance of the weld, so as to achieve a more optimal comprehensive cost performance. SUMMARY

[0006] Therefore, the present application aims to provide an acid stainless steel electrode resistant to red cracking and a preparation method thereof, which solves the problems of "redness" and "cracking" of the coating from the material system level on the premise of ensuring the mechanical strength and acid corrosion resistance of the weld, and achieves a more optimal comprehensive cost performance.

[0007] To achieve the above object, the present application provides an anti-red cracking acid stainless steel electrode in one aspect, comprising a core and a coating, the coating comprises dry powder and binder, the dry powder contains the following components in parts by weight: 30-35 parts of rutile, 5-10 parts of titanium white powder, 20-30 parts of calcined mica, 5-10 parts of feldspar, 5-10 parts of dolomite, 3-5 parts of iron powder, 10-15 parts of metallic chromium, 2-4 parts of metallic manganese, 5-9 parts of fluorite; the binder is modified potassium sodium water glass by aqueous rheological additives.

[0008] Further, the mass component content and particle size requirement of each component in the dry powder is as follows in parts by weight: Rutile: TiO2: 87-95%, particle size: 60 mesh ≤ 99%, 200 mesh ≤ 20%; Titanium white powder: TiO2: ≥98%, S ≤0.050%, P ≤0.050%, particle size: 60 mesh ≥99%, 200 mesh ≤20%; Calcined mica: SiO2: 44-58%, Al2O3: 20-33%, total amount of Na2O and K2O ≥7%, crystal water ≤0.2%, particle size: 40 mesh ≥99%, 80 mesh ≤40%; Feldspar: SiO2: 64-70%, Al2O3: 17-31%, total amount of Na2O and K2O ≥12%, particle size: 80 mesh ≥99%, 200 mesh ≤40%; Dolomite: CaCO3≥50%, MgCO3≥45%, S ≤0.030%, P ≤0.030%, particle size: 60 mesh ≥99%, 120 mesh ≤20%; Iron powder: Fe ≥99.5%, particle size: 160 mesh ≥99%; Metallic chromium: Cr ≥99.0%, Fe ≤0.30%, Si ≤0.25%, particle size: 40 mesh ≥99%, 200 mesh ≤15%; Metallic manganese: Mn ≥99.5%, C ≤0.01%, particle size: 40 mesh ≤0.1%, 200 mesh ≤15%; Fluorite: CaF2≥98%, SiO2≤1.5%, particle size: 40 mesh ≥99%, 200 mesh ≤60%.

[0009] Further, the core is HX022Cr18Ni8 core, which contains the following components in parts by weight: C≤0.03 parts, Si: 0.30-0.60 parts, Mn: 1.0-2.5 parts, P≤0.025 parts, S≤0.020 parts, Cr: 18.0-19.0 parts, Ni: 7.5-9.0 parts, Mo≤0.75 parts, Cu≤0.75 parts.

[0010] Further, the potassium sodium water glass modified by the aqueous rheological aid has a modulus of 2.3-2.7 and a viscosity of 200-250 mPa.s.

[0011] Further, the mass ratio of the aqueous rheological aid to the potassium sodium water glass is 1:30-1:50.

[0012] Further, the ratio of the thickness of the coating to the diameter of the welding core is 0.23-0.26.

[0013] Another aspect of the present application provides a preparation method of the acid stainless steel electrode resistant to red cracking, comprising the following steps: S1, dry powder is weighed according to the proportion of weight fraction, 30-35 parts of rutile, 5-10 parts of titanium white powder, 20-30 parts of calcined mica, 5-10 parts of feldspar, 5-10 parts of dolomite, 3-5 parts of iron powder, 10-15 parts of metallic chromium, 2-4 parts of metallic manganese, 5-9 parts of fluorite, and dry mixing to ensure uniform mixing; S2, binder pretreatment: adding 2-3% of the total mass of the aqueous rheological aid to the sodium potassium water glass and stirring uniformly; S3, coating preparation: adding the water glass pretreated in step S1 to S2, stirring at room temperature to obtain a wet mixed powder; S4, pressure coating treatment: through a pressure coating machine, the wet mixed powder is coated onto the surface of the welding core under suitable pressure; S5, baking treatment: adopting a segmented baking to obtain the acid stainless steel electrode resistant to red cracking.

[0014] Further, in step S2, the specific process of the binder pretreatment is adding 2-3% of the total mass of the aqueous rheological aid to the sodium potassium water glass, stirring for 20-30 minutes, and increasing the viscosity of the water glass to 200-250 mPa·s.

[0015] Further, in step S4, the specific pressure in the pressure coating treatment is 10-15 Mpa.

[0016] Further, in step S5, the specific process of the baking treatment is first baking at a low temperature of 100-150℃ for 1.5-2h, and then baking at a high temperature of 250-400℃ for 1.5-2h.

[0017] Compared with the prior art, the acid stainless steel electrode resistant to red cracking and the preparation method thereof have the following advantages: (1) The anti-red cracking acid stainless steel electrode of the present application, the dry powder formula system thereof, through the synergistic effect between components, not only ensures the weld performance in metallurgy, but also significantly enhances the anti-cracking ability of the coating in the stages of drying, red heat and welding cooling from the physical aspect, and indirectly alleviates the "redness" problem through optimizing the arc and slag behavior, realizing the unified improvement of the process performance and the weld performance.

[0018] (2) The anti-red cracking acid stainless steel electrode of the present application, through the specific particle size design of the coating powder and the selection of the binder system, improves the bonding force between the coating powder particles in the production process of pressure coating; in addition, the selected low modulus water glass has relatively mild chemical activity, and the reaction intensity with the specific mineral components in the coating powder is reduced, which can effectively inhibit the excessive generation and overflow of gas in the mixing process. This ensures that the internal structure of the coating is dense and uniform in the subsequent drying process, significantly reduces the micro-crack initiation and expansion caused by gas expansion or stress concentration, and fundamentally avoids the drying cracking and falling of the coating; the inorganic bonding network formed after the solidification of the binder system has an optimized thermal expansion characteristic, which can better match the higher thermal expansion coefficient of the austenitic stainless steel core. This improved thermal matching can significantly reduce the interfacial shear stress caused by the uneven expansion and contraction of the two during the welding thermal cycle, thereby directly improving the anti-cracking performance of the electrode during actual welding.

[0019] (3) The anti-red cracking acid stainless steel electrode of the present application, under the premise of ensuring that the mechanical strength and acid corrosion resistance of the weld fully meet the standards, solves the "redness" and "cracking" problems of the coating from the material system level, realizing a more optimal comprehensive cost performance.

[0020] (4) The preparation method of the anti-red cracking acid stainless steel electrode of the present application is simple, has the characteristics of simple process, wide and stable process conditions, and low comprehensive cost, and has excellent potential for large-scale production and commercial promotion. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with examples, the illustrative embodiments of the present application and their descriptions are only used to explain the present application, and do not limit the present application.

[0022] Example 1 S1, weigh the dry powder: 30g of rutile, 10g of titanium white, 25g of calcined mica, 5g of feldspar, 5g of dolomite, 3g of iron powder, 12g of metallic chromium, 3g of metallic manganese, and 7g of fluorite; mix the coating powder and dry mix for 30 minutes, then sieve to ensure uniform mixing of the dry powder; S2. Weigh 100g of potassium-sodium water glass with a modulus of 2.3-2.7, K:Na=1:1, and Baumé concentration of 38.0-40.0Be, add 2g of water-based rheology modifier organic modified montmorillonite, stir for 30 minutes to increase the viscosity of water glass to 200-250mPa·s, and obtain low-modulus, high-viscosity water glass. S3. Take 25g of the low-modulus, high-viscosity water glass obtained in step S2 and put it into the stirrer. Add the dry powder that was mixed evenly in step S1 to the low-modulus, high-viscosity potassium sodium water glass solution obtained in step S2. Wet mix for 25 minutes at room temperature to obtain wet mixed powder. S4. Using a pressure coating machine, the wet mixed powder is applied to the surface of the welding core HX022Cr18Ni8 with a diameter of 3.2mm and a length of 350mm under a pressure of 15Mpa. S5. Place the welding rod obtained in step S4 into an oven and bake it at a low temperature of 100°C for 2 hours; then bake it at a high temperature of 300°C for 2 hours to obtain the welding rod.

[0023] Example 2 In step S1, the following amounts of dry powder are weighed: 35g rutile, 5g titanium dioxide, 25g calcined mica, 5g feldspar, 5g dolomite, 3g iron powder, 12g metallic chromium, 3g metallic manganese, and 7g fluorite. The powders are mixed and dry-stirred for 30 minutes, then sieved to ensure that the dry powders are evenly mixed. The other steps are the same as in Example 1.

[0024] Example 3 In step S1, the following amounts of dry powder are weighed: 35g rutile, 10g titanium dioxide, 15g calcined mica, 10g feldspar, 5g dolomite, 3g iron powder, 12g metallic chromium, 3g metallic manganese, and 7g fluorite. The powder is mixed and dry-stirred for 30 minutes, then sieved to ensure that the dry powder is evenly mixed. The other steps are the same as in Example 1.

[0025] Comparative Example 1 Ordinary acidic stainless steel welding electrodes conforming to GB / T 983-2012.

[0026] Comparative Example 2 In step S2, 100g of potassium-sodium water glass with a potassium-to-sodium ratio of 1:1, M=3.05-3.15, and a viscosity of 200-250mPa·s is weighed.

[0027] The other steps are the same as in Example 3.

[0028] According to GB / T 25776-2010 "Welding material welding process performance evaluation method", and according to the welding specification in Table 1, the welding process performance of the welding rods prepared in the above examples and comparative examples is evaluated, and the results are shown in Table 2. As can be seen from the data in Table 2, compared with the ordinary acid stainless steel electrode (comparative example 1), the arc stability, welding spatter, weld forming and slag removal of the electrodes of examples 1, 2 and 3 of the present application are all better, which is specifically manifested as stable arc, small spatter, clear and beautiful weld ripples, easy slag removal, and strong overall weldability; under the same dry powder formula (example 3) and preparation process conditions, the arc stability of the electrode using conventional potassium sodium water glass as the binder (comparative example 2) is slightly lower than that of example 3 using the specific low modulus high viscosity potassium sodium water glass system. This confirms the direct influence of the binder system on the physical properties of the arc.

[0029] Table 1, welding rod welding specification Table 2, welding material welding process performance evaluation Mark at 200mm from the arc striking end of the welding rod, and weld according to the welding specification in Table 1. When the welding rod is consumed to the mark, stop immediately, and place the remaining part horizontally on the steel plate substrate at room temperature, and air cool to room temperature. Use a vernier caliper to measure and record the number and length of cracks generated in the clamping section, welding end and middle coating, and repeat the test 10 times for each group of samples.

[0030] Calculate the crack rate C according to the formula R : C R = [(Ja+Ha) / (350-200)]x10 Ja: average length of coating cracks at the clamping end (mm); Ha: average length of coating cracks at the welding end (mm); (350-200) in the denominator is the converted reference total length; 10 in the formula is the number of repetitions.

[0031] The evaluation criteria are: C R ≤1 is excellent, 1<C R ≤5 is good, and C R >5 is poor.

[0032] The test results are shown in Table 3. Data analysis shows that the crack rate C R of examples 1, 2 and 3 of the present application is all lower than 0.005, which is much lower than the excellent threshold (C R≤1), showing extremely excellent anti-cracking performance; although the anti-cracking property of the comparative electrode (Comparative Example 2) using the conventional potassium-sodium water glass is improved compared with the ordinary acid stainless steel electrode (Comparative Example 1), it is obviously insufficient compared with the same formula Example 3 using the specific low modulus and high viscosity potassium-sodium water glass system of the present application. This directly proves that the binder system of the present application plays a decisive role in improving the anti-cracking property of the coating.

[0033] Table 3, cracking of the electrode The above results show that the scheme provided by the present application not only contributes to the absolute stability of the arc, but also makes outstanding contributions to the anti-cracking property of the coating, the qualified rate of drying, etc., thereby successfully solving the long-standing core problem of "red cracking" of the coating under the premise of ensuring excellent comprehensive process performance, and realizing substantial progress in technology. In addition, the crack rate test results and the welding process performance evaluation results are consistent, which together show that the present application fundamentally solves the core problem of "cracking" of the coating by using the innovative binder and dry powder formulation system, while maintaining excellent welding process performance, and realizes substantial breakthrough in technical effect.

[0034] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An acidic stainless steel welding electrode resistant to red-heat cracking, characterized in that, It includes a core and a coating. The coating consists of dry powder and a binder. By weight, the dry powder contains the following components: 30-35 parts rutile, 5-10 parts titanium dioxide, 20-30 parts calcined mica, 5-10 parts feldspar, 5-10 parts dolomite, 3-5 parts iron powder, 10-15 parts metallic chromium, 2-4 parts metallic manganese, and 5-9 parts fluorite. The binder is potassium-sodium silicate modified with a water-based rheology modifier.

2. The acid-resistant stainless steel welding electrode resistant to red-heat cracking according to claim 1, characterized in that, The mass content and particle size requirements of each component in the dry powder, by weight, are as follows: Rutile: TiO2: 87-95%, particle size: ≥99% below 60 mesh, ≤20% below 200 mesh; Titanium dioxide: TiO2: ≥98%, S≤0.050%, P≤0.050%, particle size: ≥99% below 60 mesh, ≤20% below 200 mesh; Calcined mica: SiO2: 44-58%, Al2O3: 20-33%, total amount of Na2O and K2O ≥7%, water of crystallization ≤0.2%, particle size: ≥99% below 40 mesh, ≤40% below 80 mesh; Feldspar: SiO2: 64-70%, Al2O3: 17-31%, total amount of Na2O and K2O ≥12%, particle size: below 80 mesh ≥99%, below 200 mesh ≤40%; Dolomite: CaCO3≥50%, MgCO3≥45%, S≤0.030%, P≤0.030%, particle size: ≥99% below 60 mesh, ≤20% below 120 mesh; Iron powder: Fe≥99.5%, particle size: below 160 mesh ≥99%; Metallic chromium: Cr ≥ 99.0%, Fe ≤ 0.30%, Si ≤ 0.25%; Particle size: ≥ 99% for particles below 40 mesh, ≤ 15% for particles below 200 mesh. Metallic manganese: Mn≥99.5%, C≤0.01%, particle size: ≤0.1% for particles larger than 40 mesh, ≤15% for particles smaller than 200 mesh; Fluorite: CaF2≥98%, SiO2≤1.5%, particle size: ≥99% above 40 mesh, ≤60% below 200 mesh.

3. The acidic stainless steel welding electrode resistant to red-heat cracking according to claim 1, characterized in that: The welding core is an HX022Cr18Ni8 welding core, and by weight, the welding core contains the following components: C ≤ 0.03 parts, Si: 0.30-0.60 parts, Mn: 1.0-2.5 parts, P ≤ 0.025 parts, S ≤ 0.020 parts, Cr: 18.0-19.0 parts, Ni: 7.5-9.0 parts, Mo ≤ 0.75 parts, Cu ≤ 0.75 parts.

4. The acid-resistant stainless steel welding electrode resistant to red-heat cracking according to claim 1, characterized in that, Potassium-sodium silicate modified with water-based rheology modulators has a modulus of 2.3-2.7 and a viscosity of 200-250 mPa·s.

5. The acid-resistant stainless steel welding electrode resistant to red-heat cracking according to claim 4, characterized in that: The mass ratio of water-based rheology modifier to potassium sodium silicate is 1:30-1:

50.

6. The acid-resistant stainless steel welding electrode resistant to red-heat cracking according to claim 1, characterized in that, The ratio of the coating thickness to the core diameter is 0.23-0.

26.

7. A method for preparing an acidic stainless steel welding electrode resistant to red-heat cracking, characterized in that, Includes the following steps: S1. Weigh out the dry powder according to the following weight fractions: 30-35 parts rutile, 5-10 parts titanium dioxide, 20-30 parts calcined mica, 5-10 parts feldspar, 5-10 parts dolomite, 3-5 parts iron powder, 10-15 parts metallic chromium, 2-4 parts metallic manganese, and 5-9 parts fluorite. Mix and dry-stir to ensure the dry powder is evenly mixed. S2. Binder pretreatment: Add 2-3% of water-based rheology modifier by total mass to sodium potassium water glass, stir evenly, and obtain low-modulus, high-viscosity water glass; S3. Preparation of the drug coating: Add the pretreated water glass from step S2 to step S1, stir at room temperature to obtain a wet mixed powder; S4. Pressure coating treatment: The wet mixed powder obtained in step S3 is pressure coated onto the surface of the welding core using a pressure coating machine under appropriate pressure. S5. Baking treatment: Place the welding rod obtained in step S4 into an oven and bake it in stages to obtain acidic stainless steel welding rods that are resistant to red-hot cracking.

8. The method for preparing the acidic stainless steel welding electrode resistant to red-heat cracking according to claim 7, characterized in that: In step S2, the specific process of binder pretreatment is as follows: add 2-3% of water-based rheology modifier by total mass to sodium potassium water glass, stir for 20-30 minutes, and increase the viscosity of water glass to 200-250 mPa·s.

9. The method for preparing the acidic stainless steel welding electrode resistant to red-heat cracking according to claim 7, characterized in that: In step S4, the specific pressure during the pressure coating process is 10-15 MPa.

10. The method for preparing the acidic stainless steel welding electrode resistant to red-heat cracking according to claim 7, characterized in that: In step S5, the specific baking process is as follows: first, bake at a low temperature of 100-150℃ for 1.5-2 hours; then bake at a high temperature of 250-400℃ for 1.5-2 hours.

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