Bottom plate structure suitable for mine truck compartment and welding process

Abstract

The invention discloses a bottom plate structure suitable for a mine truck compartment and a welding process. The cargo compartment bottom plate is of a front-back sectional type butt joint transition structure, the front section is an NM450 wear-resisting steel plate with the thickness being 25 mm, the rear section is an NM500 wear-resisting steel plate with the thickness being 20 mm, and by optimizing material and thickness combination, the self weight is reduced while the wear-resisting service life is guaranteed. A wear-resistant flitch is laid on the inner side of the bottom plate, the front section is a whole plate, and the rear section is battens arranged at intervals, so that sliding friction of materials is converted into rolling friction, and wear is reduced. According to the welding process, a special combination strategy of pre-welding electromagnetic induction gradient preheating, segmented back welding, bottoming and cover face filling using different levels of welding wires is formulated, and heat preservation, slow cooling and hydrogen elimination treatment are adopted after welding. According to the method, welding stress and deformation are effectively controlled, full penetration and long fatigue life of a welding seam are ensured, and the structural quality is ensured through strict post-welding flaw detection. The wear resistance, the structural reliability and the service life of the cargo compartment bottom plate are remarkably improved on the whole.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of engineering machinery, in particular to a bottom plate structure suitable for a cargo compartment of a mine truck and a welding process. BACKGROUND

[0002] The cargo compartment of a mine dump truck bears huge impact during loading of ore materials and strong abrasion during unloading. The traditional cargo compartment bottom plate is usually made of a single material and thickness of steel plate. To cope with abrasion, the thickness of the steel plate is simply increased, which leads to excessive self-weight of the cargo compartment, affecting the carrying efficiency and energy consumption of the vehicle. Meanwhile, the abrasion of the bottom plate is not uniform in the length direction, and the rear half is particularly severely abraded due to the large pressure of material accumulation during unloading, and a single material design cannot achieve optimal economy and durability.

[0003] In terms of manufacturing, the cargo compartment bottom plate is large in size and long in weld, and large stress and deformation are easily generated during welding, and high-strength steel welding has a risk of cold cracking. If the traditional welding process is not properly handled, it will lead to problems such as insufficient weld toughness and incomplete penetration, which seriously affects the fatigue life of the weld and becomes a hidden danger for the cracking of the bottom plate structure. In addition, if the welding of the wear-resistant lining plate overlaps with the main weld of the bottom plate or the welding sequence is improper, it will further aggravate stress concentration and shorten the service life of the overall structure.

[0004] Therefore, there is an urgent need for a mine truck cargo compartment bottom plate solution that can reduce the self-weight and improve the wear resistance of different regions in a targeted manner, and ensure the structural integrity and service life through a scientific welding process. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art and provide a bottom plate structure suitable for a cargo compartment of a mine truck and a welding process. The present application effectively improves the wear resistance and service life of the cargo compartment, reduces the self-weight, and ensures the welding quality and structural reliability through the comprehensive optimization of structure, material and process.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A bottom plate structure suitable for a cargo compartment of a mine truck, the cargo compartment bottom plate is a segmented butt joint transition structure, including a front segment and a rear segment, the front segment adopts NM450 wear-resistant steel plate with a thickness of 25mm, and the rear segment adopts NM500 wear-resistant steel plate with a thickness of 20mm. By using a higher grade of wear-resistant material in the rear segment and reducing the thickness, the wear resistance of the key wear area is improved while the overall weight is reduced. The front segment and the rear segment are butt welded through a V-shaped groove with an angle of 45°, and the height-width ratio of the weld is at least 1:3 to ensure full penetration at the root of the butt weld and improve the fatigue life of the weld.

[0008] Furthermore, wear-resistant lining plates are installed on the inner side of the cargo box floor. The front section features large, single-piece wear-resistant lining plates to resist material impact and distribute load; the rear section features multiple spaced strips of wear-resistant lining plates, forming a "shock-absorbing" structure that converts the sliding friction of the underlying material into rolling friction during unloading, significantly reducing wear. The butt welds of the wear-resistant lining plates and the cargo box floor are staggered to protect the main structural welds of the floor.

[0009] The present invention also provides a welding process for the cargo box floor plate, the key of which lies in controlling welding stress and ensuring weld performance, including the following steps:

[0010] 1. Preheating before welding: Use a high-frequency electromagnetic induction heating belt to preheat the base material within a 200mm range on both sides of the area to be welded in a gradient manner. First, preheat the entire material to about 100℃, with a heating rate of 100℃ / h; when welding in sections, the sections to be welded are heated a second time to 150-200℃.

[0011] 2. Welding of the main seam of the base plate:

[0012] Root pass welding: Starting from multiple points (O1, O2, O3) in the middle of the weld and moving towards both ends, a segmented back-welding method is used. Use 50 kg flux-cored wire, current 240-260 A, voltage 26-28 V, and oscillate the welding torch in an equilateral triangle motion. The weld thickness is 4-5 mm to ensure root toughness and penetration.

[0013] Filling and capping welding: Start approximately 100mm off from the root pass starting point. Use 70kg flux-cored wire, 260-280A current, 28-30V voltage, and oscillate the welding torch in a circular motion. When capping, pause for 0.5 seconds at the bevel of the base material. The weld thickness should be 4-5mm to ensure overall strength.

[0014] 3. Post-weld treatment and inspection: Immediately after welding, cover the weld area with an insulation blanket to allow it to cool slowly. After 48 hours of insulation and hydrogen removal, grind the weld smooth and perform 100% magnetic particle testing and 100% ultrasonic testing.

[0015] 4. Welding of the wear-resistant plate: First, weld the full fillet weld around the plug holes on the wear-resistant plate. Then, weld the circumference welds using an intermittent welding method, welding 100mm intervals every 50mm. Do not weld the four rounded corners of the plate to release welding stress. After welding, allow it to stand for 48 hours and perform 100% magnetic particle testing.

[0016] The beneficial effects of this invention are:

[0017] 1. Lightweight structure and improved wear resistance: By adopting a segmented design with different materials and thicknesses, namely "front NM450 thick plate + rear NM500 thin plate", the wear resistance of the high-wear area in the rear section is specifically improved while ensuring the overall structural strength, and the weight of the cargo box is effectively reduced.

[0018] 2. Reduced unloading resistance: The spaced design of the rear strip-shaped wear-resistant plates innovatively transforms sliding friction into rolling friction, significantly reducing unloading wear and resistance.

[0019] 3. High welding quality and reliability: Through customized gradient preheating, segmented back welding, combination of different performance welding wires (root pass to ensure toughness, cover pass to ensure strength), and strict post-weld heat preservation and hydrogen removal treatment, welding cold cracks are effectively prevented, welding stress and deformation are controlled, and full penetration and high fatigue life of the weld are ensured.

[0020] 4. Stress distribution optimization: The staggered arrangement of the wear-resistant lining plate and the main weld of the base plate, the intermittent welding of the lining plate and the absence of rounded corner welding, etc., effectively avoid stress concentration and extend the service life of the structure.

[0021] 5. Controllable quality: Through multiple testing procedures, including 100% magnetic particle testing and ultrasonic testing, the welding quality from the base plate to the wear-resistant plate is fully controllable, ensuring high reliability. Attached Figure Description

[0022] Appendix Figure 1 This is a model diagram of the overall floor structure of the cargo box;

[0023] Appendix Figure 2 This is a model diagram of the main structure of the cargo box floor.

[0024] Appendix Figure 3 A welding diagram of the main structure of the cargo box floor;

[0025] Appendix Figure 4 This is a schematic diagram of the welding of wear-resistant lining plates on the cargo box floor. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0027] A structural design for the bottom plate of a mining truck cargo box is disclosed. The bottom plate 1 is a segmented butt joint transition structure. Wear-resistant plates are laid on the inner side of the bottom plate 1 to improve the service life of the cargo box. Based on the structural design of the bottom plate 1, a reasonable welding process is formulated. First, the main body weld of the bottom plate 1 is welded. Before welding, an electromagnetic induction heating belt is used to uniformly preheat the predetermined areas on both sides of the weld area. After welding, the main body weld of the bottom plate 1 is ground smooth. After the flaw detection is qualified, the weld of the laid wear-resistant plate is then welded. The root weld uses 50 kg flux-cored welding wire to ensure the toughness of the root, and the filler and cover weld uses 70 kg flux-cored welding wire to ensure the strength. After welding, the weld area is covered with an insulation blanket for slow cooling. After 48 hours of heat preservation and hydrogen removal, magnetic particle flaw detection is performed.

[0028] The core of the mining truck cargo box floor of this invention lies in the deep integration of structure and process design.

[0029] As attached Figure 1 and Figure 2 As shown, the cargo box floor 1 has a segmented butt-joint transition structure consisting of two sections of dissimilar wear-resistant steel with different thicknesses, joined together. The front section uses 25mm thick NM450 wear-resistant steel plate, and the rear section uses 20mm thick NM500 wear-resistant steel plate. This design utilizes the superior ductility and impact toughness of NM450 to increase its thickness and withstand the impact of ore materials, while leveraging the superior wear resistance of NM500 to allow for the use of thinner plates in the high-wear area of ​​the rear section, thereby achieving weight reduction. By upgrading the material grade, reducing the plate thickness, the weight of the cargo box is reduced, and the wear life is improved. The two steel plates are butt-jointed with a V-groove at a 45° angle. After welding, the aspect ratio of the weld should be strictly controlled to be no less than 1:3 to ensure full penetration welding at the root of the butt weld and improve the fatigue life of the weld.

[0030] like Figure 1 As shown, wear-resistant plates are laid on the inner side (material contact surface) of the cargo box floor 1. A single, solid wear-resistant plate 2 is laid at the front to resist direct impact from materials during loading and to distribute the impact load to the cargo box floor structure. The staggered arrangement of the wear-resistant plates and the butt welds of the floor 1 also protects the main structural welds of the floor 1. Multiple parallel strip-shaped wear-resistant plates 3 are laid at the rear of the floor 1, spaced apart to form a "shock-absorbing zone." This structure changes the sliding friction of the bottom layer of ore material at the front to rolling friction during unloading, reducing wear on the cargo box floor 1 and significantly decreasing surface wear, thereby extending the lifespan of the cargo box floor 1.

[0031] The welding process is the key to ensuring the performance of this structure. First, considering the characteristics of long straight welds with a long welding path and fast heat dissipation, before welding, a high-frequency electromagnetic induction heating tape is used to preheat the 200-mm area on both sides of the weld in a gradient manner, ensuring that the base metal temperature reaches the predetermined requirement uniformly and preventing cracks caused by rapid cooling. First, heat the entire weld to about 100°C at a heating rate of 100°C / h. At this time, adjust the heating tape to the heat preservation state. When welding the weld in segments, reheat the weld to be welded to 150 - 200°C for the second time to ensure that the predetermined temperature requirement can be achieved during the welding of each weld segment.

[0032] Next, weld the welds of the bottom plate body. The welding sequence refers to Figure 3 , and start the backing welding from the three starting points (O1, O2, O3) in the middle of the weld to both ends using the segmented backstep welding method. Starting from the welding starting point O1, weld the welds ① and ② in sequence for backing; starting from the welding starting point O2, weld the welds ③ and ④ in sequence for backing; starting from the welding starting point O3, weld the welds ⑤ and ⑥ in sequence for backing; the welds ①, ②, ③, ④, ⑤, and ⑥ are the welds extending from their respective welding starting points to both ends of the entire weld, and the welding starting points O1, O2, and O3 cannot be on the same straight line; use 50-kg class flux-cored wire for the backing welding of the welds to ensure high toughness at the root of the weld, with a current of 240 - 260°C and a voltage of 26 - 28V. During welding, the welding torch makes a regular triangular swing to ensure root penetration, and the weld thickness is 4 - 5mm. After all the backing welding of the bottom plate 1 is completed, then starting from about 100mm positions from points O1, O2, and O3 in sequence, stagger the starting points of the backing welds, and then fill and cover the welds ① - ⑥. Use 70-kg class flux-cored wire for the filling and covering welding of the welds to ensure the overall strength of the weld, with a current of 260 - 280°C and a voltage of 28 - 30V. During welding, make a circular swing to increase the weld width and depth of penetration. The size of the circle and the swing speed are adjusted according to the size of the groove. When covering, stay at the groove base metal for 0.5 seconds to melt 2 - 3mm on both sides of the groove, and the weld thickness is 4 - 5mm. At the same time, use the segmented backstep welding method for each long straight weld during backing, filling, and covering to minimize the welding stress to the greatest extent.

[0033] After the main weld is completed, conduct a 48-hour heat preservation and hydrogen removal treatment, then grind it flat and conduct 100% magnetic particle and ultrasonic flaw detection. After passing the inspection, start welding the wear-resistant patch plates. As Figure 4 shown, the wear-resistant patch plates are evenly distributed with plug weld holes. First, weld the full fillet welds around the plug weld holes, and then weld the circumferential welds of the patch plates in an intermittent welding manner of welding 100 for every 50mm. This can release the welding stress through the weld gaps, as shown in Figure 4 . It should be noted especially that the four rounded corners of the patch plates cannot be welded either. After the welding of the wear-resistant patch plates is completed, place them again for 48h, and then conduct 100% magnetic particle flaw detection.

[0034] Through the synergistic design of the above structure and process, the cargo box floor manufactured by this invention has the characteristics of lightweight, high wear resistance, long service life and high reliability, and is particularly suitable for mining dump trucks under harsh working conditions.

[0035] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A bottom plate structure suitable for mining truck cargo boxes, characterized in that, The cargo box floor (1) is a segmented butt-welding transition structure of dissimilar wear-resistant steel and dissimilar thickness, including a front section and a rear section. The wear-resistant steel plate used in the front section has lower hardness and wear resistance than that in the rear section, and the thickness of the wear-resistant steel plate in the front section is greater than that in the rear section. The front section and the rear section are butt-welded by a V-groove with a groove angle of 45° and a weld height-to-width ratio of at least 1:3, using full penetration welding.

2. The bottom plate structure suitable for mining truck cargo boxes according to claim 1, characterized in that, The inner side of the cargo box floor (1) is covered with wear-resistant lining, the front section is covered with a whole piece of wear-resistant lining (2), and the rear section is covered with strip-shaped wear-resistant lining strips (3); the strip-shaped wear-resistant lining strips (3) are arranged at intervals to form a shock-absorbing strip structure.

3. The bottom plate structure suitable for mining truck cargo boxes according to claim 2, characterized in that, The butt welds of the wear-resistant patch and the cargo box floor (1) are staggered, and the wear-resistant patch is provided with plug weld holes.

4. A welding process for a base plate structure, characterized in that, The base plate is a segmented butt joint transition structure made of dissimilar wear-resistant steels and of dissimilar thicknesses. Its welding process includes the following steps: Before welding, the base material on both sides of the area to be welded is preheated in a gradient. First, the entire material is preheated to the first preset temperature, and then locally preheated to the second preset temperature before welding. The root pass is performed using a segmented back-welding method, with the welding torch oscillating in an equilateral triangle motion. After the root pass welding is completed, fill and cover pass welding are performed, with the welding torch oscillating in a circular motion. After welding, the weld seam is ground smooth and subjected to magnetic particle and ultrasonic testing. Immediately after welding, cover the weld area with an insulation blanket to keep it warm and eliminate hydrogen for 48 hours.

5. The welding process according to claim 4, characterized in that, The starting point of the root pass welding is located in the middle of the entire weld seam, and the welding extends to both ends respectively, and the multiple welding starting points are not located on the same straight line.

6. The welding process according to claim 4, characterized in that, The starting points of the filler and cover welding are staggered by 100mm from the starting point of the root welding.

7. The welding process according to claim 4, characterized in that, The front end of the base plate is made of NM450 wear-resistant steel with a thickness of 25mm, and the rear end is made of NM500 wear-resistant steel with a thickness of 20mm. Before welding, the base material within a 200mm range on both sides of the area to be welded is preheated in a gradient. First, the entire material is preheated to 100℃, and then locally reheated to 150-200℃ before welding. The root pass is performed using a segmented back-welding method, with 50 kg flux-cored wire, a current of 240–260 A, a voltage of 26–28 V, and the welding torch is oscillated in an equilateral triangle. The weld thickness is 4–5 mm. After the root pass welding is completed, fill and cover passes are performed using 70 kg flux-cored wire, current 260-280 A, voltage 28-30 V, and the welding torch is moved in a circular motion. When covering the pass, the torch is held at the bevel of the base material for 0.5 seconds. The weld thickness is 4-5 mm. After welding, the weld seam is ground smooth and subjected to magnetic particle and ultrasonic testing. Immediately after welding, cover the weld area with an insulation blanket to keep it warm and eliminate hydrogen for 48 hours.

8. The welding process according to any one of claims 4-7, characterized in that, The inner side of the base plate is covered with a wear-resistant plate, and the wear-resistant plate is evenly distributed with plug welding holes. The welding sequence is as follows: first, weld the full fillet weld around the plug weld hole, then perform intermittent welding around the perimeter, using an interval welding method, and do not weld the four corners of the wear-resistant plate.

9. The bottom plate structure suitable for mining truck cargo boxes according to claim 8, characterized in that, After the wear-resistant plate is welded, it is placed for 48 hours and then subjected to 100% magnetic particle testing.

10. The bottom plate structure suitable for mining truck cargo boxes according to claim 8, characterized in that, The interval welding method is to weld 100mm every 50mm.

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