A welding process for austenitic ferrite 2205 duplex stainless steel plate

Abstract

The invention relates to a welding process of austenite-ferrite 2205 duplex stainless steel plate, which adopts welding materials with the same composition as that of 2205 duplex stainless steel plate, does not increase the content of Ni alloy, and reduces the alloy cost of welding materials; adopts metal arc welding, and the shielding gas is: 70%-80% Ar+18%-25% N2+1%-5% CO2; during welding, the interlayer temperature is 150-250°C, the welding current is 180-280A, the welding voltage is 25-32V, and the welding line energy is 15-25kJ / cm. The austenite in the weld structure finally obtained reaches 45%-55%, and the rest is ferrite, and the mechanical properties of the weld are Rp0.2≥450MPa, Rm≥655MPa, and -40°C Akv≥47J.

Description

Technical Field

[0001] The invention relates to the technical field of welding, and in particular to a welding process for an austenitic-ferrite 2205 duplex stainless steel plate. Background Art

[0002] 2205 duplex stainless steel refers to a type of stainless steel whose microstructure consists of two phases, ferrite and austenite. It has the advantages of both ferritic stainless steel and austenitic stainless steel, namely, good plasticity, toughness, strength and corrosion resistance. It is widely used in many fields such as petrochemical industry, energy industry, transportation, etc.

[0003] Duplex stainless steel is difficult to weld. The welding parameters and the composition of the welding materials have a great influence on the metallographic structure ratio of the welded joint and directly affect the performance of the welded joint. The cooling speed of the welding process is faster than that of the steel plate rolling process. If the composition of the welding material is the same as that of the steel plate, too much ferrite will be produced in the weld and heat-affected zone, thereby reducing the corrosion resistance and toughness of the welded joint. Therefore, more Ni elements are generally added to the welding materials, and the proportion of austenite in the weld is increased by using Ni to expand the austenite zone, thereby improving the performance of the weld, such as 2209 welding materials.

[0004] The Chinese invention patent with the authorization announcement number CN 110253125B discloses "a plasma welding process of duplex stainless steel 2205 with bypass wire feeding", and the welding wire uses AWS A5.9: ER2209 welding wire; the back shielding gas and the welding front shielding gas are both mixed gases of 98% argon and 2% nitrogen; the plasma gas and the drag hood gas are both argon with a purity level of 99.99%. The Chinese patent application with the publication number CN102019485A discloses a "duplex stainless steel welding method", which uses 99.99% argon inert gas protection for manual tungsten inert gas welding, and the welding wire is Lincoln LNT4462φ2.0, AWSA5.9: ER2209. However, the Ni content in the ER2209 welding wire reaches 9%, and the high addition of Ni as a precious alloy directly increases the cost of welding materials. Summary of the invention

[0005] The invention provides an austenite-ferrite 2205 duplex stainless steel plate welding process, adopts welding materials with the same composition as the 2205 duplex stainless steel plate, does not increase the Ni alloy content, and reduces the alloy cost of the welding material; adopts ternary gas protection, and the austenite in the obtained weld structure reaches 45% to 55%, and the rest is ferrite, and has excellent mechanical properties.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A welding process for austenitic ferrite 2205 duplex stainless steel plate, comprising:

[0008] 1) Use welding wire with the same composition as 2205 duplex stainless steel plate;

[0009] 2) The welding method is metal arc welding, and the shielding gas composition is: 70% to 80% Ar + 18% to 25% N2 + 1% to 5% CO2;

[0010] 3) During the welding process, the interlayer temperature is 150-250°C, the welding current is 180-280A, the welding voltage is 25-32V, and the welding line energy is 15-25kJ / cm.

[0011] Furthermore, the chemical composition of the welding wire is calculated by weight percentage: C 0.01%~0.030%, Si0.4%~0.60%, Mn 0.9%~1.30%, Cr 22.0%~23.0%, Ni 5.50%~6.50%, Mo 3.00%~3.50%, N 0.145%~0.20%, P≤0.030, S≤0.015%, and the balance is Fe and unavoidable impurities.

[0012] Furthermore, the 2205 duplex stainless steel plate adopts a V-shaped or X-shaped groove, the groove angle is 30° to 80°, the groove gap is 2 to 4 mm, and the groove blunt edge is 2 to 4 mm.

[0013] Furthermore, the flow rate of the protective gas is 15 to 25 L / min.

[0014] Furthermore, the proportion of austenite in the weld metal structure is 45% to 55%, and the rest is ferrite; the weld mechanical properties are Rp0.2≥450MPa, Rm≥655MPa, and -40℃Akv≥47J.

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

[0016] By using ternary gas protection and welding materials with the same composition as 2205 duplex stainless steel plate, and matching appropriate welding processes, the austenite ratio of the weld is 45% to 55%, and the rest is ferrite. It has excellent mechanical properties, effectively improves the welding quality, and reduces the welding cost. DETAILED DESCRIPTION

[0017] The austenitic ferrite 2205 duplex stainless steel plate welding process of the present invention comprises:

[0018] 1) Use welding wire with the same composition as 2205 duplex stainless steel plate;

[0019] 2) The welding method is metal arc welding, and the shielding gas composition is: 70% to 80% Ar + 18% to 25% N2 + 1% to 5% CO2;

[0020] 3) During the welding process, the interlayer temperature is 150-250°C, the welding current is 180-280A, the welding voltage is 25-32V, and the welding line energy is 15-25kJ / cm.

[0021] Furthermore, the chemical composition of the welding wire is calculated by weight percentage: C 0.01%~0.030%, Si0.4%~0.60%, Mn 0.9%~1.30%, Cr 22.0%~23.0%, Ni 5.50%~6.50%, Mo 3.00%~3.50%, N 0.145%~0.20%, P≤0.030, S≤0.015%, and the balance is Fe and unavoidable impurities.

[0022] Furthermore, the 2205 duplex stainless steel plate adopts a V-shaped or X-shaped groove, the groove angle is 30° to 80°, the groove gap is 2 to 4 mm, and the groove blunt edge is 2 to 4 mm.

[0023] Furthermore, the flow rate of the protective gas is 15 to 25 L / min.

[0024] Furthermore, the proportion of austenite in the weld metal structure is 45% to 55%, and the rest is ferrite; the weld mechanical properties are Rp0.2≥450MPa, Rm≥655MPa, and -40℃Akv≥47J.

[0025] The austenite-ferrite 2205 duplex stainless steel plate welding process of the present invention adopts welding materials with the same composition as the 2205 duplex stainless steel plate, does not increase the Ni alloy content, and reduces the alloy cost of the welding materials.

[0026] 2205 duplex stainless steel plate adopts V-shaped or X-shaped groove, with groove angle of 30°~80°, groove gap of 2~4mm, and groove blunt edge of 2~4mm to ensure the melting and filling of welding wire.

[0027] The welding method adopts metal arc welding, the shielding gas composition is: 70% to 80% Ar + 20% to 25% N2 + 1% to 5% CO2, and the gas flow rate is 15 to 25 L / min.

[0028] In the shielding gas, the main function of Ar is to protect the alloy elements in the welding wire from oxidation and burning. The main function of N2 is to incorporate more N into the welding pool to ensure that the N content of the weld is 0.2% to 0.5%. The principle is as follows: N, like Ni, is an element that forms and expands austenite, but N's ability to expand the austenite zone is much greater than Ni. High-temperature N is also more capable of stabilizing austenite than Ni. Increasing the proportion of N in the shielding gas can promote the integration of N into the weld metal. The appropriate N content can increase the proportion of austenite in the weld metal, while excessive N2 may form nitrogen pores; therefore, the present invention controls the proportion of nitrogen to 20% to 25%. Appropriate CO2 can improve the droplet refinement rate, improve the stability of the welding arc, and thus improve the forming performance of the weld metal. The present invention controls CO2 to 1% to 5%.

[0029] During welding, the interlayer temperature is 150-250℃, the welding current is 180-280A, the welding voltage is 25-32V, and the welding line energy is 15-25kJ / cm. The lower the interlayer temperature, the faster the weld metal cools down. The greater the line energy heat input, the slower the weld metal cools down. Appropriate interlayer temperature and line energy can increase the proportion of austenite in the weld metal.

[0030] The following embodiments are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0031] [Example]

[0032] The chemical compositions of the duplex stainless steel plates and welding wires in each embodiment are shown in the following table:

[0033] Table 1 Chemical composition of steel plate and welding wire (wt%)

[0034]

[0035] The welding method of each embodiment adopts metal arc welding, the specification of the welding wire is Φ1.2mm or Φ1.6mm, and the welding process parameters are shown in Table 2. Before welding, the groove is cleaned to remove pollutants such as oil.

[0036] Table 2 Welding process parameters

[0037]

[0038] The composition of the weld metal obtained after welding is shown in Table 3.

[0039] Table 3 Weld metal composition

[0040]

[0041] The mechanical properties and metal structure of the weld are shown in Table 4.

[0042] Table 4 Mechanical properties and microstructure of weld

[0043]

[0044] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A welding process for austenitic ferrite 2205 duplex stainless steel plate, characterized in that: include: 1) Use welding wire with the same composition as 2205 duplex stainless steel plate; 2) The welding method is metal arc welding, and the shielding gas composition is: 70%~80% Ar + 18%~25% N2 + 1%~5% CO2; 3) During welding, the flow rate of shielding gas is 15-25L / min; the interlayer temperature is 150-250℃, the welding current is 180-280A, the welding voltage is 25-32V, and the welding line energy is 15-25 kJ / cm; The proportion of austenite in the weld metal structure is 45% to 55%, and the rest is ferrite; the mechanical properties of the weld are Rp0.2 ≥ 450MPa, Rm ≥ 655MPa, -40℃ Akv ≥ 47J.

2. The austenitic ferrite 2205 duplex stainless steel plate welding process according to claim 1, characterized in that: The chemical composition of the welding wire is calculated by weight percentage as follows: C 0.01%-0.030%, Si 0.4%-0.60%, Mn 0.9%-1.30%, Cr 22.0%-23.0%, Ni 5.50%-6.50%, Mo 3.00%-3.50%, N 0.145%-0.20%, P≤0.030, S≤0.015%, and the balance is Fe and unavoidable impurities.

3. The austenitic ferrite 2205 duplex stainless steel plate welding process according to claim 1, characterized in that: The 2205 duplex stainless steel plate adopts a V-shaped or X-shaped groove, the groove angle is 30° to 80°, the groove gap is 2 to 4 mm, and the groove blunt edge is 2 to 4 mm.

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