Welding process of soft magnetic steel and low alloy high strength structural steel

Abstract

The application discloses a welding process of soft magnetic steel and low-alloy high-strength structural steel, welding surfaces of the soft magnetic steel and the low-alloy high-strength structural steel are the same, and each includes an upper welding inclined surface and a lower welding surface; the welding surfaces of the soft magnetic steel and the low-alloy high-strength structural steel are parallel to each other and form an X-shaped welding groove after being matched; the welding of the soft magnetic steel and the low-alloy high-strength structural steel adopts multi-layer and multi-pass welding, welding current is 110-170 A, voltage is 21-23 V, welding speed is 69-130 mm / min, and the temperature of each layer is controlled in the range of 100-150 DEG C. Small line energy and small specification welding are adopted, the influence of material difference is reduced, the welding quality of the soft magnetic steel and the low-alloy high-strength structural steel is ensured, and welding defects such as cracks generated in the welding process are prevented; the heat input amount in unit time is reduced, the welding deformation of the functional part is ensured, and the influence of welding on the magnetism of the soft magnetic steel is effectively controlled.

Description

Technical Field

[0001] This invention belongs to the field of dissimilar steel welding technology, specifically relating to a welding process for soft magnetic steel and low-alloy high-strength structural steel. Background Technology

[0002] Soft magnetic steel is a commonly used material for guide rails in high-speed maglev trains. Due to the high operating speeds of high-speed maglev trains, they require significant guiding forces when subjected to lateral disturbances or traversing curves with large curvatures. Therefore, the main mechanical performance requirements for soft magnetic steel used in guide rails in high-speed maglev systems are as follows:

[0003] Table 1 Tensile property requirements for soft magnetic steel

[0004]

[0005] For the Charpy (V-notch) impact test of soft magnetic steel, the impact absorbed energy shall not be less than 27J at a test temperature of -10℃; at a test temperature of -25℃, the single value of one specimen shall be less than 27J, but shall not be less than 21J.

[0006] Table 2 Bending Test of Soft Magnetic Steel

[0007]

[0008] As a functional component for magnetic levitation guidance, the welding of soft magnetic steel and low-alloy high-strength structural steel is crucial. This involves two main challenges: ensuring weld quality between dissimilar materials and overcoming the impact of high-temperature welding on the magnetic properties of the soft magnetic steel. If conventional welding methods are used, the following technical defects are highly likely to occur:

[0009] 1) Due to the differences between the two materials, welding defects such as cracks are easily generated after welding;

[0010] 2) High-temperature welding can easily affect the magnetism of soft magnetic steel;

[0011] 3) Welding causes welding deformation to functional components.

[0012] In summary, the current welding process has technical defects. Improving the handling of material differences, welding deformation, and the impact on the magnetism of soft magnetic steel are urgent problems that need to be solved. Summary of the Invention

[0013] The purpose of this invention is to overcome the shortcomings of the prior art and provide a welding process for soft magnetic steel and low alloy high-strength structural steel in which the weld seam meets the mechanical performance requirements of soft magnetic steel after welding.

[0014] To achieve the above objectives, this invention provides a welding process for soft magnetic steel and low-alloy high-strength structural steel. The welding surfaces of the soft magnetic steel and the low-alloy high-strength structural steel are identical, both including an upper welding bevel and a lower welding surface. The intersection lines of the upper and lower welding bevels are arranged outwards, and the angles between the upper welding bevel and the vertical plane, and between the lower welding bevel and the vertical plane, are equal. After the welding surfaces of the soft magnetic steel and the low-alloy high-strength structural steel are aligned in parallel, an X-shaped welding bevel is formed.

[0015] The welding of soft magnetic steel and low alloy high-strength structural steel adopts multi-layer multi-pass welding. The welding material is low-hydrogen sodium type welding rod, the welding current is 110~170A, the voltage is 21~23V, the welding speed is 69~130mm / min, and the temperature of each layer is controlled at 100~150℃.

[0016] Furthermore, the angle between the upper welding slope and the vertical plane, and the angle between the lower welding slope and the vertical plane are both 30° to 45°, and the ratio of the height of the upper welding slope to the height of the lower welding slope is 2:1 to 3:1.

[0017] Furthermore, after the welding surfaces of the soft magnetic steel and the low-alloy high-strength structural steel are aligned in parallel, a gap of 1-2 mm is left between the intersection lines of the soft magnetic steel and the intersection lines of the low-alloy high-strength structural steel.

[0018] Furthermore, before welding, the welding surface of the soft magnetic steel and the upper and lower horizontal surfaces of the soft magnetic steel, as well as the area within 30-50mm of the welding surface, are ground and cleaned. Correspondingly, the welding surface of the low alloy high strength structural steel and the upper and lower horizontal surfaces of the low alloy high strength structural steel, as well as the area within 30-50mm of the welding surface, are also ground and cleaned.

[0019] Furthermore, the welding diameter of each layer is 3.2~4mm.

[0020] Furthermore, the outermost two to three layers of the upper welded slope are segmented on both sides and lap-welded, with the welding speed, voltage, current, temperature and diameter of the segments in the same layer being equal.

[0021] Further, the chemical composition of the soft magnetic steel, by mass percentage, includes C: 0.022~0.07%, Si: 1.40~1.60%, Mn: 0.20~0.60%, P≤0.012%, S≤0.002%, Cr: 0.40~0.80%, Cu: 0.40~0.90%, Ni: 0.20~0.70%, Nb: 0.010~0.040%, V: 0.003~0.01%, Ti: 0.003~0.03%, Alt: 0.02~0.045%, Mo: 0.003~0.01%, N: 0.002~0.010%, with the balance being Fe and unavoidable impurities; and 1.2%≤Cu+Ni+Cr++Mo≤1.5%, 0.03%≤Nb+V+Ti≤0.060%.

[0022] Furthermore, the carbon equivalent of both the soft magnetic steel and the low-alloy high-strength structural steel is 0.38~0.42%.

[0023] Furthermore, the low-alloy high-strength structural steel is designated as Q355B.

[0024] Furthermore, the low-hydrogen sodium-type welding electrode is model E5015.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1) The use of low heat input and small-scale welding reduces the impact of material differences, ensures the welding quality of soft magnetic steel and low-alloy high-strength steel, and prevents welding defects such as cracks during the welding process;

[0027] 2) The welding process of the present invention reduces the amount of heat input per unit time, ensures the welding deformation of functional parts, and effectively controls the magnetic effect of welding on soft magnets. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the welding bevel of the present invention. Detailed Implementation

[0029] The present invention will be further described in detail with reference to specific embodiments and accompanying drawings to facilitate a clearer understanding of the invention, but these descriptions do not constitute a limitation on the invention.

[0030] The two types of steel used in the dissimilar steel welding of this invention are soft magnetic steel and low-alloy high-strength structural steel. The chemical composition of the soft magnetic steel, by mass percentage, includes: C: 0.022~0.07%, Si: 1.40~1.60%, Mn: 0.20~0.60%, P≤0.012%, S≤0.002%, Cr: 0.40~0.80%, Cu: 0.40~0.90%, Ni: 0.20~0.70%, Nb: 0.010~0.0 40%, V: 0.003~0.01%, Ti: 0.003~0.03%, Alt: 0.02~0.045%, Mo: 0.003~0.01%, N: 0.002~0.010%, with the balance being Fe and unavoidable impurities; and 1.2%≤Cu+Ni+Cr++Mo≤1.5%, 0.03%≤Nb+V+Ti≤0.060%; the low-alloy high-strength structural steel conforms to the standard GB / T1591. The tensile properties of this soft magnetic steel are shown in Table 3:

[0031] Table 3

[0032]

[0033] The key element for achieving the function of soft magnetic steel is the silicon (Si) content, which can improve the electromagnetic properties and resistivity of the steel. However, when its content exceeds 1.60%, it easily forms a mixed-grain structure, resulting in low-temperature impact toughness in the heat-affected zone of the welded joint. Simultaneously, it is an embrittlement element, affecting the plasticity, toughness, and weldability of the base metal. Therefore, both types of steel exhibit excellent weldability when the carbon equivalent is between 0.38% and 0.42%.

[0034] The welding process for soft magnetic steel and low-alloy high-strength structural steel is as follows:

[0035] like Figure 1 As shown, the welding surfaces of the soft magnetic steel and the low-alloy high-strength structural steel are the same, both including an upper welding bevel and a lower welding surface. The intersection lines of the upper and lower welding bevels are arranged outwards. The angles between the upper welding bevel and the vertical plane, and between the lower welding bevel and the vertical plane, are equal, both between 30° and 45°. The ratio of the height of the upper welding bevel to the height of the lower welding bevel is 2:1 to 3:1. After the welding surfaces of the soft magnetic steel and the low-alloy high-strength structural steel are aligned in parallel, an X-shaped welding groove is formed, and a gap of 1 to 2 mm is left between the intersection lines of the soft magnetic steel and the low-alloy high-strength structural steel.

[0036] Grinding and cleaning are performed on the welding surface of the soft magnetic steel and on the upper and lower horizontal surfaces of the soft magnetic steel, within 30-50mm of the welding surface. Similarly, grinding and cleaning are performed on the welding surface of the low alloy high strength structural steel and on the upper and lower horizontal surfaces of the low alloy high strength structural steel, within 30-50mm of the welding surface.

[0037] The welding of soft magnetic steel to low-alloy high-strength structural steel adopts multi-layer, multi-pass welding. The welding material is low-hydrogen sodium-type welding rod, the welding current is 110~170A, the voltage is 21~23V, the welding speed is 69~130mm / min, the temperature of each layer is controlled at 100~150℃, and the welding diameter of each layer is 3.2~4mm. To control welding deformation, the outermost two to three layers on the upper welding slope are segmented and lapped on both sides. The welding speed, voltage, current, temperature, and diameter of each segment in the same layer are equal.

[0038] Example

[0039] The low-alloy high-strength structural steel is designated as Q355B, conforming to standard GB / T1591-2018. The chemical composition of the soft magnetic steel and Q355B by weight percentage is shown in Table 4. The thickness of both is 35mm.

[0040] Table 4

[0041]

[0042] The welding material used is E5015 low-hydrogen sodium type welding electrode. This electrode has a stable arc, good resistance to porosity, stable mechanical properties, and good plasticity, impact toughness, and crack resistance. The properties of welding material E5015 are shown in Table 5.

[0043] Table 5 Properties of Welding Materials

[0044]

[0045] The angle between the upper welding slope and the vertical plane, and the angle between the lower welding slope and the vertical plane are both 30°, and the height ratio of the upper welding slope to the lower welding slope is 2:1; after the welding surfaces of the soft magnetic steel and the low alloy high strength structural steel are parallel and joined together, an X-shaped welding groove is formed, and a gap of 2mm is left between the intersection line of the soft magnetic steel and the intersection line of the low alloy high strength structural steel.

[0046] The welding surfaces of the soft magnetic steel and the upper and lower horizontal surfaces of the soft magnetic steel, within 50mm of the welding surfaces, are all ground and cleaned. Similarly, the welding surfaces of the low alloy high strength structural steel and the upper and lower horizontal surfaces of the low alloy high strength structural steel, within 50mm of the welding surfaces, are all ground and cleaned.

[0047] The welding of soft magnetic steel and low alloy high-strength structural steel adopts multi-layer multi-pass welding, and the interpass temperature is controlled below 150℃, as shown in Table 6.

[0048] Table 6 Arc Welding Process Parameters

[0049]

[0050] After welding, mechanical property tests were conducted on the weld according to the process qualification test standard NB47014-2011. Tensile, impact, and bending tests were performed, and the test data are as follows:

[0051] Tensile test

[0052] Table 7 Tensile test results of welded joints

[0053]

[0054] Impact test

[0055] Table 8 Impact test results of welded joints

[0056]

[0057] The average impact energy was much greater than 21J; among them, the impact energy value of the impact test conducted at a test temperature of -25℃ was higher than 27J.

[0058] Bending test

[0059] Table 9

[0060]

[0061] The results of mechanical performance tests and bending tests show that the joint combination of soft magnetic steel and low alloy high-strength structural steel welded using low-hydrogen sodium-type welding rods and welding processes achieves mechanical properties comparable to those of soft magnetic steel used in guide rails in high-speed maglev systems, thus meeting the design requirements of functional components.

Claims

1. A welding process for soft magnetic steel and low-alloy high-strength structural steel, characterized in that: The welding surfaces of the soft magnetic steel and the low-alloy high-strength structural steel are the same, both including an upper welding bevel and a lower welding surface. The intersection lines of the upper and lower welding bevels are arranged outwards, and the angles between the upper and lower welding bevels and the vertical plane are equal. After the welding surfaces of the soft magnetic steel and the low-alloy high-strength structural steel are aligned in parallel, an X-shaped welding groove is formed. The angles between the upper and lower welding bevels and the vertical plane are equal, both between 30° and 45°, and the ratio of the height of the upper welding bevel to the height of the lower welding bevel is 2:1 to 3:

1. After the welding surfaces of the soft magnetic steel and the low-alloy high-strength structural steel are aligned in parallel, a gap of 1 to 2 mm is left between the intersection lines of the soft magnetic steel and the low-alloy high-strength structural steel. Before welding, the welding surface of the soft magnetic steel and the upper and lower horizontal surfaces of the soft magnetic steel, as well as the area within 30-50mm of the welding surface, are ground and cleaned. Correspondingly, the welding surface of the low alloy high strength structural steel and the upper and lower horizontal surfaces of the low alloy high strength structural steel, as well as the area within 30-50mm of the welding surface, are ground and cleaned. The welding of soft magnetic steel and low-alloy high-strength structural steel adopts multi-layer multi-pass welding. The welding material is low-hydrogen sodium type welding rod, the welding current is 110~170A, the voltage is 21~23V, the welding speed is 69~130mm / min, and the temperature of each layer is controlled at 100~150℃. The outermost two to three layers of the upper welding slope adopt segmented and lap welding on both sides. The welding speed, voltage, current, temperature and diameter of the segments in the same layer are equal. The chemical composition of the soft magnetic steel, by mass percentage, includes C: 0.022~0.07%, Si: 1.40~1.60%, Mn: 0.20~0.60%, P≤0.012%, S≤0.002%, Cr: 0.40~0.80%, Cu: 0.40~0.90%, Ni: 0.20~0.70%, Nb: 0.010~0.040%, V: 0.003~0.01%, Ti: 0.003~0.03%, Alt: 0.02~0.045%, Mo: 0.003~0.01%, N: 0.002~0.010%, with the balance being Fe and unavoidable impurities; and 1.2%≤Cu+Ni+Cr++Mo≤1.5%, 0.03%≤Nb+V+Ti≤0.060%; The low-alloy high-strength structural steel is of type Q355B; the low-hydrogen sodium-type welding electrode is of type E5015.

2. The welding process of soft magnetic steel and low-alloy high-strength structural steel according to claim 1, characterized in that: The welding diameter of each layer is 3.2~4mm.

3. The welding process of soft magnetic steel and low-alloy high-strength structural steel according to claim 1, characterized in that: The carbon equivalent of both the soft magnetic steel and the low-alloy high-strength structural steel is 0.38~0.42%.

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