Mine support welding process based on Q345B material

Abstract

The invention discloses a mine support welding process based on a Q345B material. The mine support welding process comprises the following steps: (1) pretreatment before welding; (2) selecting a welding material: adopting an E5015-G low-hydrogen sodium type welding rod; (3) welding parameter control: backing welding current is 90-110A, and backing welding voltage is 22-24V; the filling welding current is 160-180 A, and the filling welding voltage is 24-26 V; the cosmetic welding current is 140-160 A, and the cosmetic welding voltage is 25-28 V; and (4) post-welding treatment is conducted, specifically, after welding is completed, post-heat dehydrogenation treatment is conducted at the temperature of 250-300 DEG C for 1-2 h, and stress relief annealing is conducted at the temperature of 600-650 DEG C according to requirements. The invention aims to solve the problems of insufficient welding joint strength, low impact toughness and difficulty in control of welding deformation in the prior art, and the mechanical property and the service safety of a mine bracket welding structure are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of metal welding technology, and in particular to a welding process for mine supports based on Q345B material. Background Technology

[0002] Hydraulic supports are coal mining face equipment that uses high-pressure liquid as power and is composed of dozens of hydraulic components (cylinders, valves) and some metal components to support and control the roof. They have the characteristics of high strength, fast movement speed, good support performance, and safety and reliability [1]. As a key load-bearing structure in underground mining operations, the performance of mine supports is directly related to the safety and efficiency of mining operations. With the increasing development of deep mineral resources, mine supports need to withstand more complex loads and harsher environmental erosion, which puts forward higher requirements for the strength, toughness and welding performance of materials. Q345B, as a low alloy high strength structural steel, is widely used in the field of mining machinery manufacturing due to its excellent comprehensive mechanical properties and good processing technology. However, Q345B material is prone to cold cracking and heat-affected zone performance deterioration during welding, and traditional welding processes cannot fully utilize its material potential. Hydraulic supports are mostly made of materials with high rigidity and have a complex structural design. They are thick plate box structures, and the structures can be welded together for fixation and reinforcement. The amount of welding is large and there are many welds. Therefore, if an unreasonable welding scheme is adopted during the welding process, it is easy to cause welding deformation and poor welding quality, which will have a certain impact on the stability of the hydraulic support [3]. The welding process proposed in this patent effectively overcomes the above defects through systematic parameter optimization and process control, and provides technical guarantee for the high-quality manufacturing of Q345B mining supports. Hydraulic supports are key equipment for underground mining operations, and their performance is directly related to mining safety and efficiency. Q345B steel is widely used in the manufacturing of mining supports due to its high strength, good toughness and economy. However, the traditional welding process has the following problems:

[0003] Insufficient welded joint strength: prone to cold cracking and deterioration of the heat-affected zone, resulting in joint strength lower than that of the base material.

[0004] 1) Low impact toughness: Especially in low temperature environments (such as -20℃), the impact absorption energy is difficult to meet the requirements of harsh working conditions in mines (≥34J).

[0005] 2) Welding deformation is difficult to control: Due to the high strength of the materials and the large amount of welding (mostly thick plate box structures), the release of residual stress can easily lead to significant deformation (>1.5mm / m), affecting the stability and safety of the support. 3) Existing technologies cannot simultaneously achieve joint strength, toughness, and deformation control, and there is an urgent need to optimize welding process parameters and process control. Summary of the Invention

[0006] The purpose of this invention is to provide a welding process for mine supports based on Q345B material. By systematically optimizing the selection of welding materials, preheating temperature control, welding parameter settings, and post-weld heat treatment processes, this invention solves the problems of insufficient weld joint strength, low impact toughness, and difficulty in controlling welding deformation in existing technologies, and significantly improves the mechanical properties and service safety of the welded structure of the mine support.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] This invention discloses a welding process for mine supports based on Q345B material, comprising:

[0009] Welding material selection: Use E5015-G low-hydrogen sodium type welding rods; the electrode diameter should be selected according to the plate thickness, using φ3.2mm for root pass or φ4.0mm for filler and cover pass; before welding, the electrode should be dried at 350-400℃ for 1-2 hours and stored in an 80-100℃ heat-insulating container for immediate use, ensuring the moisture content is ≤0.15%;

[0010] Pre-welding treatment:

[0011] Beveling: V-shaped bevels are prepared by plasma cutting or machining, with an angle of 60°±5°, a blunt edge of 1-2mm, a gap of 2-3mm, and a surface roughness of Ra≤25μm. Oxide scale, burrs and oil stains are removed.

[0012] Preheating process: When the plate thickness is ≥16mm, use electric heating to preheat the whole plate to 80-120℃;

[0013] Assembly and positioning: Rigid fixing method is adopted. The tack weld length is 30-50mm, the spacing is 200-300mm, and the height does not exceed 2 / 3 of the designed weld thickness;

[0014] Welding parameter optimization: DC reverse polarity is adopted; specific parameters are shown in the table below:

[0015] Welding layers Electrode diameter (mm) Welding current A Arc voltage V Welding speed (cm / min) Heat input kJ / cm root pass welding 3.2 90-110 22-24 12-15 12-15 Filler weld 4 160-180 24-26 15-18 18-22 Cover weld 4 140-160 25-28 18-22 15-18

[0016] During the welding process, maintain a short arc operation and use a sawtooth or crescent-shaped oscillation with an amplitude ≤ 3 times the electrode diameter; for multi-layer and multi-pass welding, slag must be thoroughly removed and the weld surface must be visually inspected 100%;

[0017] Post-welding treatment:

[0018] Post-weld heat removal: Immediately after welding, perform heat treatment at 250-300℃ for 1-2 hours, followed by slow cooling at a rate of ≤100℃ / h to ambient temperature;

[0019] Stress-relieving annealing: Important load-bearing components are annealed as a whole; heating temperature is 600-650℃; cooling method is furnace cooling, cooling rate ≤150℃ / h, and air cooling after reaching 300℃.

[0020] Deformation correction: Mechanical correction method is adopted, correction temperature ≤600℃, direct flame heating correction is prohibited.

[0021] Furthermore, after the welding rods are dried, they are stored in an 80-100℃ heat-insulating container and used for no more than 4 hours. Wet welding rods need to be dried again, and the number of times they are dried should not exceed 2.

[0022] Furthermore, the interpass temperature is controlled between 80-250℃ during the welding process, and an infrared thermometer is used for real-time monitoring, with the measuring point 50±5mm away from the edge of the bevel.

[0023] Furthermore, the holding time for stress-relief annealing is calculated based on a plate thickness of 25 mm / h and a minimum holding time of 2 hours, with a cooling rate ≤100℃ / h, and the plate is cooled to below 300℃ before being removed from the furnace and air-cooled.

[0024] Further welding parameters:

[0025] Root pass welding: φ3.2mm E5015-G welding rod, current 100A, voltage 23V, speed 13cm / min;

[0026] Filler welding: φ4.0mm E5015-G welding electrode, current 170A, voltage 25V, speed 16cm / min;

[0027] Cover welding: φ4.0mm E5015-G welding rod, current 150A, voltage 26V, speed 20cm / min.

[0028] Furthermore, the interlayer temperature is controlled at 150℃.

[0029] Furthermore, hydrogen removal treatment is performed immediately after welding at 250℃ for 1.5 hours.

[0030] Furthermore, the annealing parameters are: 600℃ × 2h stress-relief annealing.

[0031] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0032] Excellent mechanical properties: the tensile strength of the welded joint reaches 490-550MPa (fracture at the base material), the impact absorption energy at -20℃ is ≥34J (the measured average is 42J), and the maximum hardness of the heat-affected zone is ≤220HV10 (below the cold crack sensitivity threshold of 270HV10).

[0033] Precise deformation control: Welding deformation is controlled within 1.5mm / m (e.g., the maximum deflection of a 6m support is 8.5mm and the lateral bending is 2.3mm).

[0034] Significant economic benefits: When applied in the production of hydraulic support columns, the first-pass yield rate increased from 82% to 96%, the welding defect rate decreased by 75%, and annual cost savings were approximately 500,000 yuan. Attached Figure Description

[0035] The present invention will be further described below with reference to the accompanying drawings.

[0036] Figure 1 A schematic diagram showing the welding bevel type and dimensions for mine supports;

[0037] Figure 2 This is a schematic diagram of the welding thermal cycle curve;

[0038] Figure 3 Micrograph of the welded joint (×200);

[0039] Figure 4 It is a column for a Q345B hydraulic support. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to the accompanying drawings.

[0041] Example 1 (taking the Q345B hydraulic support column as an example):

[0042] Material: Q345B steel plate, 16mm thick.

[0043] Beveling: according to Figure 1 Machining V-shaped bevel (60°, blunt edge 1.5mm, gap 2.5mm).

[0044] Preheating: The entire unit is preheated to 100℃ using electric heating (temperature measuring point 50mm from the bevel).

[0045] welding:

[0046] Root pass welding: φ3.2mm E5015-G welding rod, current 100A, voltage 23V, speed 13cm / min.

[0047] Filler welding: φ4.0mm E5015-G welding rod, current 170A, voltage 25V, speed 16cm / min.

[0048] Cover welding: φ4.0mm E5015-G welding rod, current 150A, voltage 26V, speed 20cm / min.

[0049] The interlayer temperature is controlled at 150℃.

[0050] Post-welding:

[0051] Immediately after welding, perform hydrogen removal treatment at 250℃ for 1.5 hours; then slowly cool to ambient temperature at a rate of 100℃ / hour.

[0052] Overall stress-relief annealing at 600℃ for 2 hours (holding time calculated based on plate thickness).

[0053] Mechanical straightening of deformation (temperature ≤600℃).

[0054] 100%UT + 20%MT test (Level I qualified).

[0055] Performance verification: The columns produced according to the above process were tested and found to have the following properties: tensile strength 510MPa (breaks at the base material), impact energy at -20℃ 42J, maximum deflection 8.5mm (6m length), and a first-pass yield of 96%.

[0056] The proposed welding process for mine supports based on Q345B material significantly improves the strength, toughness, crack resistance, and dimensional stability of the welded joints through scientific material selection, precise temperature control (dynamic matching model), optimized parameters ("low hydrogen input + stepped heat input"), and effective post-weld treatment. This process is simple to operate, highly versatile, and can be directly applied to existing production lines, possessing significant engineering value and economic importance for promoting the efficient application of Q345B material in the field of mine supports.

[0057] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A mine support welding process based on Q345B material, characterized in that: include: (1) Pre-welding treatment: Use V-groove with an angle of 60°±5°, blunt edge of 1-2mm, and gap of 2-3mm. Preheat steel plates with a thickness of ≥16mm at 80-120℃. (2) Selection of welding materials: Use E5015-G low-hydrogen sodium type welding rods with a diameter of 3.2-4.0mm, and dry them at 350-400℃ for 1-2 hours before welding; (3) Welding parameter control: root pass welding current 90-110A, voltage 22-24V; fill pass welding current 160-180A, voltage 24-26V; cover pass welding current 140-160A, voltage 25-28V; (4) Post-weld treatment: immediately after welding, perform heat treatment at 250-300℃ for 1-2 hours to remove hydrogen, and perform stress relief annealing at 600-650℃ as required.

2. The welding process of mine support based on Q345B material according to claim 1, characterized in that: After drying, the welding rods are stored in an 80-100℃ heat preservation cylinder and used for no more than 4 hours. Wet welding rods need to be dried again, and the number of times they are dried should not exceed 2.

3. The welding process of mine support based on Q345B material according to claim 1, characterized in that: During the welding process, the interpass temperature is controlled between 80-250℃ and monitored in real time using an infrared thermometer. The temperature measuring point is 50±5mm away from the edge of the bevel.

4. The welding process of mine support based on Q345B material according to claim 1, characterized in that: The holding time for stress-relief annealing is calculated based on a plate thickness of 25 mm / h and a minimum holding time of 2 hours. The cooling rate is ≤100℃ / h, and the plate is cooled to below 300℃ before being removed from the furnace and air-cooled.

5. The welding process of mine support based on Q345B material according to claim 1, characterized in that: welding: Root pass welding: φ3.2mm E5015-G welding rod, current 100A, voltage 23V, speed 13cm / min; Filler welding: φ4.0mm E5015-G welding electrode, current 170A, voltage 25V, speed 16cm / min; Cover welding: φ4.0mm E5015-G welding rod, current 150A, voltage 26V, speed 20cm / min.

6. The welding process of mine support based on Q345B material according to claim 5, characterized in that: The interlayer temperature is controlled at 150℃.

7. The welding process of mine support based on Q345B material as claimed in claim 5, wherein: Immediately after welding, perform hydrogen removal treatment at 250℃ for 1.5 hours.

8. The welding process of mine support based on Q345B material as claimed in claim 5, wherein: Annealing parameters: 600℃×2h stress-relief annealing.

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