What is the impact of high humidity environment on welding defects of electric scooters?

What effect does a high humidity environment have on welding defects of electric scooters?

1. Effect of high humidity environment on welding materials

1.1 Hygroscopicity of welding materials
Welding materials have significant hygroscopicity in high humidity environments. For example, materials such as welding rod coatings and fluxes have strong hygroscopicity. When the relative humidity reaches more than 80%, the hygroscopicity of welding rod coatings can increase by more than 30%. This is because welding rod coatings are mainly composed of inorganic and organic matter, and organic components such as wood powder easily absorb moisture in high humidity environments. The hygroscopicity of flux cannot be ignored. Its hygroscopicity increases with the increase of humidity. When the humidity rises from 30% to 90%, the hygroscopicity of flux can increase by about 25%. This hygroscopicity will cause a water film to form on the surface of the welding material, affecting the stability of the welding process.
1.2 Changes in welding material properties
High humidity environments have many effects on the performance of welding materials. First, after the welding rod coating absorbs moisture, its melting characteristics will change. Experiments show that the melting speed of the electrode coating slows down by about 15% after moisture absorption, which reduces the amount of shielding gas generated during welding and worsens the protection effect. Secondly, after the flux absorbs moisture, its fluidity deteriorates and the spreading coefficient decreases by about 20%, affecting the forming quality of the weld. In addition, the mechanical properties of the welding material will also decrease. The tensile strength of the weld metal after moisture absorption decreases by about 10%, and the impact toughness decreases by about 15%. This is mainly because the hydrogen produced by the decomposition of water during the welding process will remain in the weld, forming pores and microcracks, thereby reducing the mechanical properties of the weld.

2. The influence of high humidity environment on welding process

2.1 Adjustment of welding current and voltage
The high humidity environment has a significant impact on the setting of welding current and voltage. Since the arc stability deteriorates after the welding material absorbs moisture, in order to maintain a stable welding process, it is usually necessary to adjust the welding current and voltage.
In a high humidity environment, the welding current needs to be increased by about 10% - 15%. This is because the water film formed on the surface of the welding material after moisture absorption increases the resistance of the arc, resulting in an increase in the arc voltage. In order to ensure the normal burning of the arc and the transition of the molten droplet, the welding current needs to be appropriately increased to compensate for the increase in the arc voltage. For example, when using arc welding with electrodes, when the relative humidity rises from 40% to 80%, in order to maintain a stable welding process, the welding current needs to be increased from 150A to about 165A.
The welding voltage also needs to be adjusted accordingly. Since the melting speed of the welding material slows down after absorbing moisture, in order to ensure the depth and width of the weld, the welding voltage needs to be reduced by about 5% - 10%. Reducing the welding voltage can increase the arc length and make the arc heat more concentrated, thereby increasing the transition frequency of the molten droplet and the melting speed of the molten droplet, which helps to improve the forming quality of the weld. For example, in carbon dioxide gas shielded welding, when the relative humidity rises from 30% to 70%, the welding voltage needs to be reduced from 25V to about 23.5V.
2.2 Changes in welding speed and shielding gas flow
The high humidity environment also has an important impact on the welding speed and shielding gas flow.
The welding speed needs to be appropriately reduced. Since the melting speed of the welding material slows down after absorbing moisture, in order to ensure the penetration depth and width of the weld, the welding speed needs to be reduced. Experiments show that in a high humidity environment, the welding speed needs to be reduced by about 15% - 20%. For example, in manual arc welding, when the relative humidity rises from 50% to 90%, the welding speed needs to be reduced from 30 cm per minute to about 24 - 25 cm per minute. Reducing the welding speed can increase the arc's residence time on the weld, so that the molten droplet has enough time to transition and melt, thereby improving the forming quality of the weld.
The shielding gas flow rate needs to be increased. Since the amount of shielding gas generated after the welding material absorbs moisture decreases, the protection effect becomes worse. In order to ensure the quality of the weld, the shielding gas flow rate needs to be increased. In a high humidity environment, the shielding gas flow rate needs to be increased by about 20% - 30%. For example, in argon arc welding, when the relative humidity rises from 40% to 80%, the shielding gas flow rate needs to be increased from 15 liters per minute to about 18 - 19 liters per minute. Increasing the flow rate of shielding gas can better remove moisture and impurities from the welding area, improve the protective effect of shielding gas, and reduce porosity and oxidation in the weld.

3. The impact of high humidity environment on welding defects

3.1 Increased porosity defects
High humidity environment significantly increases the probability of porosity defects during welding. When the welding material absorbs moisture, the moisture decomposes into hydrogen and oxygen at the high temperature of welding. These gases are difficult to escape in the molten pool and eventually form pores. Studies have shown that the porosity is about 40% higher when welding at a relative humidity of 80% than when welding at a relative humidity of 30%. For example, in the welding of the frame of an electric scooter, the number of pores in the weld increases significantly in a high humidity environment. These pores reduce the density and strength of the weld, affect the overall structural stability of the frame, and may cause safety hazards such as weld cracking during use.
3.2 Increased risk of crack defects
The risk of crack defects increases significantly when welding in a high humidity environment. After the welding material absorbs moisture, the hydrogen generated by the decomposition of water will remain in the weld. During the cooling process of the weld, hydrogen tends to gather in the stress concentration area, forming hydrogen-induced cracks. Experimental data show that when the relative humidity rises from 40% to 80%, the probability of hydrogen-induced cracks in the weld increases from 5% to about 20%. In addition, high humidity causes the performance of welding materials to deteriorate, and the tensile strength and impact toughness of the weld metal are reduced, making the weld more prone to cracks when subjected to external forces. In the wheel hub welding part of the electric scooter, the cracks generated by welding in a high humidity environment may expand due to vibration and impact during the driving of the vehicle, seriously affecting the connection strength between the wheel hub and the frame, threatening riding safety.
3.3 Poor weld formation
High humidity environment has many adverse effects on the quality of weld formation. After the welding material absorbs moisture, the melting speed slows down and the fluidity deteriorates, making it difficult to control the weld depth and weld width. Experiments show that in a high humidity environment, the weld depth decreases by about 10% and the weld width narrows by about 15%. At the same time, the arc stability deteriorates, the molten droplet transition is uneven, and defects such as undercut and depression appear on the weld surface. In the welding of the handlebars of electric scooters, the appearance quality of the weld welded in a high humidity environment is poor, and the undercut phenomenon is serious, which not only affects the appearance, but also reduces the load-bearing capacity of the weld, affecting the handling performance and safety of the handlebar.

4. The impact of high humidity environment on the welding quality of electric scooters

4.1 Hidden dangers of frame structure strength

The impact of high humidity environment on the welding quality of electric scooter frames is mainly reflected in the following aspects:
Strength reduction caused by pore defects: As mentioned above, the porosity generated by welding in a high humidity environment increases significantly. The presence of these pores will reduce the density of the weld, making the weld prone to stress concentration when bearing loads. Experimental data show that for every 10% increase in porosity, the tensile strength of the weld will decrease by about 15%. For the frame of an electric scooter, the frame is the main load-bearing structure of the entire vehicle, and the decrease in its weld strength will directly affect the overall structural stability of the frame. In actual use, the vehicle will be subjected to various complex loads during driving, such as the impact force caused by bumpy roads, the weight of the rider, etc. If the weld strength is insufficient, the frame may crack or even break during use, causing serious safety accidents.
Safety hazards caused by crack defects: The risk of hydrogen-induced cracks caused by welding in a high humidity environment increases significantly. These cracks are formed during the cooling process of the weld and may further expand during subsequent use. Studies have shown that the length of hydrogen-induced cracks is usually between a few millimeters and a few centimeters, and the width is between tens of microns and hundreds of microns. The presence of these cracks will seriously weaken the strength of the weld, making the weld more likely to break when subjected to external forces. In the welding parts of the frame of the electric scooter, such as the joints of the frame, the welding points of the support rods, etc., if cracks occur, the structural integrity of the frame may be damaged. During vehicle driving, especially when driving at high speeds or making sharp turns, insufficient frame strength may cause the vehicle to lose balance and increase the risk of riders falling.
4.2 Reduced durability of welding parts
The impact of high humidity environment on the durability of welding parts of electric scooters is mainly reflected in the following aspects:
Intensified corrosion of welds: High humidity environment provides favorable conditions for the corrosion of welds. Defects such as pores and microcracks generated during welding make the weld surface rougher and easy to absorb moisture and impurities. These moisture and impurities will react chemically with the metal components in the weld, resulting in faster corrosion of the weld. Experimental data show that in a high humidity environment, the corrosion rate of the weld is about 3-5 times higher than in a dry environment. For the welding parts of electric scooters, such as the connection between the frame and the connection between the wheel hub and the frame, the corrosion of the weld will reduce its durability. During long-term use, the corrosion of the weld may cause the strength of the weld to further decrease, or even the weld to fall off, thus affecting the normal use of the vehicle.
Shortened fatigue life: Defects such as pores, cracks, and undercuts generated by welding in a high humidity environment will reduce the fatigue strength of the weld. Fatigue strength refers to the maximum stress that a material can withstand under alternating loads. Experimental studies have shown that defects such as pores and cracks in welds can become the initiation source of fatigue cracks. Under the action of alternating loads, these cracks will continue to expand and eventually lead to fatigue fracture of the weld. For electric scooters, the vehicle will be subjected to various alternating loads during driving, such as bumps on the road and the trampling of riders. The fatigue life of welds welded in a high humidity environment will be greatly shortened due to the presence of many defects. For example, the fatigue life of welds welded in a normal environment may reach more than 10^6^ cycles, while the fatigue life of welds welded in a high humidity environment may be reduced to about 10^5^ cycles. This means that fatigue fracture may occur in the welding part in a relatively short period of time, affecting the service life and safety of the vehicle.

5. Detection and prevention of welding defects of electric scooters in high humidity environments

5.1 Selection of detection methods
In high humidity environments, the detection of welding defects of electric scooters is crucial. For different types of defects, appropriate detection methods need to be selected.
Porosity defect detection: For porosity defects, radiographic testing (RT) and ultrasonic testing (UT) can be used. Radiographic testing can clearly show the location and size of pores inside the weld, with high detection sensitivity, and can detect pores with a diameter greater than 0.5mm. Ultrasonic testing uses the propagation characteristics of ultrasonic waves in the weld to detect porosity defects. It has a fast detection speed and is suitable for the detection of large-area welds. Studies have shown that the detection rate of porosity defects by ultrasonic testing can reach more than 85%.
Crack defect detection: Magnetic particle testing (MT) and penetration testing (PT) can be used to detect crack defects. Magnetic particle testing is suitable for surface and near-surface crack detection of ferromagnetic materials, with high detection sensitivity, and can detect cracks with a width of less than 0.1mm. Penetrant testing is suitable for surface crack detection of non-ferromagnetic materials. Through the penetration and imaging of the penetrant in the crack, the location and length of the crack can be clearly displayed. Experimental data show that the detection rate of crack defects by penetrant testing can reach more than 90%.
Poor weld formation detection: For poor weld formation, such as undercuts, depressions and other defects, visual inspection and dimensional measurement can be used. Visual inspection can intuitively find defects on the weld surface. The inspector observes the appearance quality of the weld with the naked eye and records the location and degree of the defects. Dimension measurement uses a measuring tool to measure the depth of penetration, width of the weld and other dimensions to determine whether the weld formation meets the requirements. Through the combination of these two methods, poor weld formation defects can be effectively detected to ensure the appearance quality and dimensional accuracy of the weld.
5.2 Implementation of preventive measures
In order to reduce the occurrence of welding defects of electric scooters in high humidity environments, effective preventive measures must be taken.
Control the humidity of the welding environment: Before welding, a dehumidifier should be used to control the relative humidity of the welding area below 40%. Studies have shown that when the relative humidity is lower than 40%, the moisture absorption of welding materials is significantly reduced, and the probability of defects such as pores and cracks is reduced by about 60%. In addition, desiccants can be set in the welding area to further reduce the moisture content in the air and ensure the dryness of the welding environment.
Welding material processing: welding materials should be properly stored in high humidity environments. Welding rods should be stored in a dry environment and need to be dried before use. The drying temperature is 150℃ - 200℃ and the insulation time is 1-2 hours. The flux also needs to be heated before use. The heating temperature is 250℃ - 300℃ and the insulation time is 30-60 minutes. Through these treatments, the hygroscopicity of welding materials can be effectively reduced and the welding quality can be improved.
Optimize welding process parameters: According to the characteristics of high humidity environments, reasonably adjust welding process parameters. Appropriately increase welding current by 10% - 15%, reduce welding voltage by 5% - 10%, reduce welding speed by 15% - 20%, and increase shielding gas flow by 20% - 30%. Through these adjustments, the stability of the arc can be improved, the melting and protection effects of the weld can be improved, and the occurrence of welding defects can be reduced.
Strengthen the monitoring of the welding process: During the welding process, a dedicated person should be arranged to monitor the welding process. The monitoring personnel need to observe the stability of the arc, the transition of the molten droplet, and the forming quality of the weld in real time, and promptly discover and correct abnormal conditions in the welding process. At the same time, automated welding equipment can be used to improve the stability and consistency of the welding process and reduce the impact of human factors on the welding quality.

6. Repair method for welding defects of electric scooters in high humidity environments

6.1 Selection of repair process
For various defects generated during the welding process of electric scooters in high humidity environments, it is necessary to select a suitable repair process according to the defect type and location.
Porosity defect repair: For porosity defects, local repair welding can be used for repair. First, use a grinding wheel or angle grinder to clean the weld surface around the pores, remove the oxide scale and impurities, and then use the same welding materials and processes as the original welds for repair welding. When repairing welding, the welding current and voltage should be controlled to avoid the generation of new pores. For larger pores, layered repair welding can be used, and the thickness of each layer of repair welding is controlled at about 2-3mm to ensure the density and strength of the weld.
Crack defect repair: The repair of crack defects needs to be handled with caution. For surface cracks, carbon arc gouging or grinding can be used to clean the cracks, and then repair welding can be performed. Before repair welding, the welding area should be preheated. The preheating temperature is determined according to the material and thickness of the parent material, generally between 100℃-200℃. When repair welding, low-hydrogen welding materials should be used to control the welding heat input to avoid the recurrence of cracks. For internal cracks, non-destructive testing methods such as ultrasonic testing can be used to determine the length and location of the cracks, and then repair them by drilling crack stop holes or repair welding. When drilling crack stop holes, the hole diameter is generally 6-8mm, and the position should be at the end of the crack. When repair welding, welding should be started from the end of the crack and gradually proceed to the middle of the crack to ensure complete repair of the crack.
Repair of poor weld formation: For poor weld formation, such as undercuts, depressions and other defects, a combination of grinding and repair welding can be used for repair. First, use a grinding wheel or angle grinder to grind the undercut or depression flat, and then use the same welding materials and processes as the original weld for repair welding. When repairing welding, the welding current and voltage should be controlled so that the weld penetration and width meet the design requirements. For undercut defects, the weld surface needs to be trimmed after repair welding to make its appearance quality meet the requirements.
6.2 Evaluation of repair effect
The repaired welding parts need to be strictly evaluated to ensure that the repair effect meets the use requirements.
Appearance quality inspection: The surface of the repaired weld should be smooth and flat, without defects such as undercuts, depressions, pores, cracks, etc. The weld penetration and width should meet the design requirements, and the transition between the weld and the base material should be naturally smooth. Appearance quality inspection can be carried out by visual inspection and dimensional measurement. The inspector should inspect the repaired weld in accordance with the relevant welding quality standards and record the inspection results.
Nondestructive testing: For the repaired welding parts, nondestructive testing should be carried out to ensure that there are no defects inside the weld. Radiographic testing (RT), ultrasonic testing (UT), magnetic particle testing (MT) or penetrant testing (PT) can be used for testing. Radiographic testing can clearly show defects such as pores and cracks inside the weld, with high detection sensitivity; ultrasonic testing is suitable for detecting cracks, unfused defects inside the weld, and has a fast detection speed; magnetic particle testing is suitable for surface and near-surface crack detection of ferromagnetic materials; penetrant testing is suitable for surface crack detection of non-ferromagnetic materials. Nondestructive testing should be performed by professional testing personnel, and the test results should be evaluated according to relevant testing standards.
Mechanical property testing: The repaired welding parts should be tested for mechanical properties to ensure that their strength and toughness meet the requirements. The repaired welds can be tested by tensile testing, bending testing, impact testing and other methods. Tensile testing can determine the tensile strength and yield strength of the weld; bending testing can test the plasticity of the weld; impact testing can determine the impact toughness of the weld. Mechanical property tests should be carried out in accordance with relevant standards, and the repaired welds should be evaluated based on the test results. If the test results do not meet the requirements, they need to be repaired and tested again until they meet the use requirements.

7. Summary
The high humidity environment has a negative impact on the welding quality of electric scooters in many aspects, mainly reflected in the changes in welding material properties, the difficulty in adjusting welding process parameters, and the increase in welding defects. Through detailed research and experimental data, we can draw the following conclusions:
7.1 Influence of welding materials and processes
Welding material hygroscopicity: The hygroscopicity of welding materials is significantly enhanced in high humidity environments, and the moisture absorption of electrode coatings and flux increases with the increase in humidity, resulting in the formation of a water film on the surface of the welding material, affecting the stability of the welding process.
Welding material performance changes: After hygroscopic welding materials, the melting speed slows down, the amount of shielding gas generated decreases, the fluidity deteriorates, and the mechanical properties decrease. For example, the tensile strength of the weld metal after hygroscopic welding is reduced by about 10%, and the impact toughness is reduced by about 15%. This is mainly due to the hydrogen generated by the decomposition of water remaining in the weld, forming pores and microcracks.
Welding process adjustment: In a high humidity environment, the welding current needs to be increased by about 10% - 15%, the welding voltage needs to be reduced by about 5% - 10%, the welding speed needs to be reduced by about 15% - 20%, and the shielding gas flow rate needs to be increased by about 20% - 30%. These adjustments help maintain the stability of the welding process, but increase the complexity and cost of the welding operation.
7.2 Increase in welding defects
Porosity defects: High humidity environments significantly increase the probability of porosity defects. Studies have shown that in an environment with a relative humidity of 80%, the porosity is about 40% higher than that in an environment with a relative humidity of 30%. The presence of pores reduces the density and strength of the weld and affects the overall structural stability of the frame.
Crack defects: The risk of hydrogen-induced cracks generated by welding in a high humidity environment increases significantly. Experimental data show that when the relative humidity increases from 40% to 80%, the probability of hydrogen-induced cracks in the weld increases from 5% to about 20%. Crack defects will seriously weaken the strength of the weld, causing the weld to break more easily during use.
Poor weld formation: The high humidity environment causes the weld penetration depth to decrease by about 10%, the weld width to narrow by about 15%, and defects such as undercut and depression appear on the weld surface. These defects not only affect the appearance quality of the weld, but also reduce the load-bearing capacity of the weld, affecting the handling performance and safety of the electric scooter.
7.3 Impact of welding quality and durability
Hidden dangers of frame structure strength: The pores and cracks caused by welding in a high humidity environment will significantly reduce the tensile strength and fatigue strength of the weld. Experimental data show that for every 10% increase in porosity, the tensile strength of the weld will decrease by about 15%. These defects may cause the weld to crack or even break during use, causing serious safety accidents.
Reduced durability of welding parts: The high humidity environment provides favorable conditions for the corrosion of the weld, and the corrosion rate of the weld is about 3-5 times higher than that in a dry environment. In addition, welding defects will reduce the fatigue life of the weld and shorten its service life.
7.4 Detection and preventive measures
Detection methods: For welding defects generated in high humidity environments, methods such as radiographic detection, ultrasonic detection, magnetic particle detection and penetration detection can be used for detection. These methods can effectively detect defects inside and on the surface of the weld and ensure welding quality.
Preventive measures: By controlling the humidity of the welding environment, properly storing welding materials, optimizing welding process parameters and strengthening welding process monitoring, the occurrence of welding defects can be effectively reduced. For example, using dehumidification equipment to control the relative humidity of the welding area below 40% can significantly reduce the moisture absorption of the welding material and the probability of defects.
In summary, the impact of high humidity environment on the welding quality of electric scooters is multifaceted and has a significant negative impact. By taking effective detection and preventive measures, the occurrence of welding defects can be effectively reduced, the welding quality can be improved, and the safety and durability of electric scooters can be ensured.