A thick plate dissimilar steel welding process

Abstract

The application discloses a kind of thick plate dissimilar steel welding process, thick plate is the steel plate of thickness 100-60mm, welding steel is Q420qDZ35 steel and ZG300-500H steel, including the following processes: steel plate surface treatment, layered welding, weld design, preheating before welding, moisture removal before welding, back treatment, heat treatment after welding, temperature detection.The application effectively avoids the dilution of weld structure by base material by designing groove angle and joint form and selecting reasonable welding material.Meanwhile, the application provides a flat butt pad welding method to ensure the penetration of welded joint and good welding quality.The application realizes the flat butt joint of cast steel and high-strength steel with thickness of 100-60mm and the welding process of thick plate dissimilar steel by selecting reasonable welding material.The application has low cost, high welding efficiency, good process stability and reliability, can reduce linear energy, control the fusion ratio of welding joint, obtain qualified welded joint, and the performance of weld meets the needs of high-temperature strength and high-temperature operating conditions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of welding, and relates to a welding method for thick plate dissimilar steel, in particular to a welding method for a hinge steel bridge pier post anchor system of dissimilar steel cast steel. BACKGROUND

[0002] The main problem of welding of low alloy high strength steel with different strength levels is welding cold cracking in fusion zone and weld zone, and tempering softening loss of strength in heat affected zone, researches are mainly concentrated in adjusting the strength and toughness matching of the welded joint, controlling the microstructure and texture of each region of the welded joint, and optimizing the welding process to improve the weldability. The welding problems of steels with different compositions and microstructures mainly include dilution of weld metal, generation of martensitic brittle layer and carbon migration and diffusion layer, and distribution of residual stress of the joint. From the aspect of chemical composition of low alloy steel, with the increase of the content of alloying elements in the steel, the hardenability of the steel increases, which greatly affects the weldability. The content of alloying elements in the weld metal is mainly affected by the fusion ratio, and the fusion ratio depends on multiple factors, including the groove form, welding parameters and the melting characteristics and thermal conductivity of the metal. The generation of the transition layer in the fusion zone will reduce the performance of the joint and become a weak link of the joint, and the decarburized layer is also prone to intergranular corrosion when operating at high temperature. The uneven thermal expansion and thermal contraction of dissimilar steel will cause the distribution of welding residual stress to be different from that of the same metal, and the residual stress cannot be effectively eliminated by tempering, but only causes redistribution of the residual stress.

[0003] For different welding materials, it is necessary to develop targeted welding process, including pre-welding heat treatment, welding heat input, welding speed, heat preservation measures during welding, post-weld cooling speed and heat treatment process and other factors. The existing welding process cannot effectively guarantee the reliability of the welding of thick plate dissimilar steel in the present project, and related welding research tests need to be carried out to scientifically analyze and improve the welding materials and welding process. SUMMARY

[0004] In order to overcome the deficiencies of the prior art, the present application discloses a welding process for thick plate dissimilar steel. The purpose of the present application is to provide a welding process technology for thick plate dissimilar steel, and the thickness of the thick plate can reach 100 mm.

[0005] The present application is realized by the following technical scheme:

[0006] A welding process for thick plate dissimilar steel, the thick plate is a steel plate with a thickness of 60-100 mm, the welding steel is Q420qDZ35 steel and ZG300-500H steel, and the welding process comprises the following processes:

[0007] (1) Steel plate surface treatment: after the welding steel plate and welding materials are prepared, the surface of the steel plate is pretreated to remove rust; joint cleaning: the to-be-welded area is polished to expose the metal color.

[0008] (2) Layered welding: when welding 1-2 layers: adopting shielded metal arc welding, welding current is 220-240A, arc voltage is 28-30V, welding speed is 18-20cm / min, welding heat input is not more than 15J / cm; interlayer temperature is 180-220℃; when welding 3 layers or more: adopting shielded metal arc welding, welding current is 240-260A, arc voltage is 30-32V, welding speed is 20-22cm / min, welding heat input is not more than 17J / cm; interlayer temperature is 180-220℃.

[0009] (3) Welding opening design: the welding groove is V-shaped, the groove angle is 45°, the groove gap is 0-1mm, and the misalignment amount is not more than 1mm.

[0010] (4) Preheating before welding: preheating conditions: ambient temperature is lower than 5℃, or the plate thickness is greater than 25mm and preheating is needed; preheating range: 150-200mm on both sides of the welding opening; preheating temperature: 150-200℃.

[0011] (5) Drying before welding: when the air humidity is greater than 80%, drying is adopted by using a drying gun before welding.

[0012] (6) Back treatment: ceramic gasket is pasted at the bottom of the weld.

[0013] (7) Post-welding heat treatment: 500-580℃, holding for 2-3h.

[0014] (8) Temperature detection method: after heating is stopped, measurement is conducted on the bottom surface of the welded part, and the temperature detection instrument is a point thermometer.

[0015] The high-strength steel Q420qDZ35 disclosed by the application has the following components: C≤0.11%, Mn 1.0%-1.7%, Si≤0.55%, S≤0.005%, P≤0.025%, the balance being Fe and inevitable impurity elements, the yield strength is ≥410MPa, the tensile strength is ≥540MPa, the elongation is ≥19%, and the impact absorption energy at-20℃ is ≥120J; the above-mentioned contents are in mass percentage.

[0016] The cast steel ZG300-500H disclosed by the application has the following components: C 0.17-0.25%, Mn 1.0-1.6%, Si≤0.6%, S≤0.025%, P≤0.025%, Ni≤0.4%, Cr≤0.35%, Mo≤0.15%, V≤0.05%, Ni≤0.4%, Cu≤0.4%, the balance being Fe and inevitable impurity elements, the yield strength is ≥300MPa, the tensile strength is ≥500MPa, and the elongation is ≥20%, the above-mentioned contents are in mass percentage.

[0017] The component of the welding wire ER55-G is: C≤0.12%, Mn≤1.75%, Si≤0.8%, S≤0.03%, P≤0.03%, Ni 0.8-1.1%, Cr≤0.15%, Mo≤0.35%, V≤0.05%, the balance is Fe and inevitable impurity elements, the deposited metal-30 DEG C low temperature impact energy is ≥27J, the yield strength of the welding wire is ≥470MPa, the tensile strength is 550-690MPa, and the elongation is ≥19%, and the above content is in percentage by mass.

[0018] The present application has the advantages that by designing the groove angle and the joint form and selecting reasonable welding materials, the dilution of the weld structure by the base material is effectively avoided, and a flat butt joint gasket welding method is provided to ensure that the welded joint is fully penetrated and has good welding quality. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a groove design schematic diagram of two kinds of dissimilar steels in the welding process of the embodiment.

[0020] Figure 2 It is a welding pass sequence and welding pass arrangement diagram in the welding process of the embodiment.

[0021] A is a girder welding piece, B is a cast steel welding piece, and C is a ceramic gasket. DETAILED DESCRIPTION

[0022] The present application is further described below in combination with specific embodiments, and the specific embodiments are further descriptions of the principles of the present application, and do not limit the present application in any way, and the same or similar technologies of the present application do not exceed the protection scope of the present application.

[0023] In combination with the drawings.

[0024] The implementation standard of the Q420qDZ35 steel plate of the embodiment is the GB / T 714-2015 standard, and the implementation standard of Z35 is the GB / T5313-2010. The performance acceptance value is: Rm≥720MPa; Rel≥580MPa; A≥15%; the key points of the welding and heat treatment of the Q420qDZ35 steel plate and the Z35 material are as follows:

[0025] The Q420qDZ35 steel plate finally needs to be subjected to post-weld heat treatment at 500-580 ℃ for 2-3 h. The base material 20MnMoNb meets the welding requirements, but still has a large tendency of quenching and welding cold crack sensitivity. Therefore, in order to prevent the Q420 / 20MnMoNb welded joint from appearing post-weld cold cracks, the weldability of the steel can be improved by preheating before welding. According to the empirical formula of the minimum preheating temperature T0 / ℃ before welding and combined with the actual production, the preheating temperature of the Q420 / 20MnMoNb dissimilar steel T-shaped welding test plate can be determined to be 150-200 ℃.

[0026] Figure 1 The schematic diagram of the welding groove structure used for the welding process is shown in Figure 2 The bead sequence and bead arrangement in the welding process of the embodiment are shown in the figure. In the figure, the girder welding piece A is Q420qDZ35 steel, and the cast steel welding piece B is ZG300-500H steel.

[0027] The welding process includes the following steps:

[0028] 1) Base material preparation: material Q420qDZ35+ZG300-500H, size 60+100 mm; as shown in Figure 1 and Figure 2 , in the figure, the girder welding piece A is Q420qDZ35 steel, and the cast steel welding piece B is ZG300-500H steel.

[0029] 2) Welding material preparation: welding wire ER55-G, size Φ1.2, in accordance with the standard GB / T 8110-2020.

[0030] 3) Welding sequence:

[0031] ① Steel plate surface treatment: the steel plate surface is treated by pre-treatment rust removal.

[0032] ② Base material heat treatment: preheating temperature: 150-200 ℃. Preheating range: 150-200 mm on both sides of the welding opening. Preheating condition: the ambient temperature is lower than 5 ℃, or the plate thickness is greater than 25 mm, which needs to be preheated. Post-weld heat treatment: 500-580 ℃, for 2-3 h.

[0033] ③ Welding: the welding method is gas shielded arc welding, and the welding specification is shown in the table:

[0034]

[0035] ④ Internal quality butt welds require 100% UT, and BⅠlevel is qualified.

[0036] ⑤ Appearance quality All welds shall not have cracks, lack of fusion, slag inclusions, weld lumps and lack of filling of craters, etc. The weld appearance shall be smooth transition, the weld surface shall not be uneven, and spatter marks around shall be strictly prohibited.

Claims

1. A welding process for thick plate dissimilar steels, characterized in that: The thick plate is a steel plate with a thickness of 60-100 mm, the welding steel type is Q420qDZ35 steel and ZG300-500H steel, and the welding process comprises the following processes: (1) Steel plate surface treatment: the steel plate surface is pretreated to remove rust; Joint cleaning: polishing the area to be welded to expose the metal color; (2) Layered welding: when welding 1-2 layers: using shielded metal arc welding, welding current is 220-240 A, arc voltage is 28-30 V, welding speed is 18-20 cm / min, welding heat input is not more than 15 J / cm; interlayer temperature is 180-220 DEG C; when welding 3 layers or more: using shielded metal arc welding, welding current is 240-260 A, arc voltage is 30-32 V, welding speed is 20-22 cm / min, welding heat input is not more than 17 J / cm; interlayer temperature is 180-220 DEG C; (3) Weld opening design: the weld groove is V-shaped, the groove angle is 45 DEG, the groove gap is 0-1 mm, and the misalignment amount is not more than 1 mm; (4) Preheating before welding: preheating conditions: ambient temperature is lower than 5 DEG C, or the plate thickness is greater than 25 mm and preheating is required; preheating range: 150-200 mm on both sides of the weld; preheating temperature: 150-200 DEG C; (5) Drying before welding: when the air humidity is greater than 80%, drying is used before welding; (6) Back treatment: ceramic gasket is attached at the bottom of the weld; (7) Post-weld heat treatment: 500-580 DEG C, holding for 2-3 h; (8) Temperature detection method: after heating stops, the temperature is measured at the bottom of the welded part, and the measuring point is within 30-50 mm from the weld.

2. The welding process of thick plate dissimilar steel according to claim 1, characterized in that: The composition of the high-strength steel Q420qDZ35 is: C≤0.11%, Mn 1.0%-1.7%, Si≤0.55%, S≤0.005%, P≤0.025%, the balance being Fe and inevitable impurity elements, the yield strength is≥410 MPa, the tensile strength is≥540 MPa, the elongation is≥19%, and the impact energy at-20 DEG C is≥120 J; the above contents are in mass percent.

3. The welding process of thick plate dissimilar steel according to claim 1, characterized in that: The composition of the cast steel ZG300-500H is: C 0.17-0.25%, Mn 1.0-1.6%, Si≤0.6%, S≤0.025%, P≤0.025%, Ni≤0.4%, Cr≤0.35%, Mo≤0.15%, V≤0.05%, Ni≤0.4%, Cu≤0.4%, the balance being Fe and inevitable impurity elements, the yield strength is≥300 MPa, the tensile strength is≥500 MPa, the elongation is≥20%, and the above contents are in mass percent.

4. The welding process of thick plate dissimilar steel according to claim 1, characterized by: The composition of the welding wire ER55-G is: C≤0.12%, Mn≤1.75%, Si≤0.8%, S≤0.03%, P≤0.03%, Ni 0.8-1.1%, Cr≤0.15%, Mo≤0.35%, V≤0.05%, the balance being Fe and unavoidable impurities, the deposited metal has a low-temperature impact energy at -30℃≥27J, the yield strength of the welding wire is≥470MPa, the tensile strength is 550-690MPa, and the elongation is≥19%, the above contents being in mass percent.

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