【Daily Question】【Static Equipment – AC Version...Question 140】August 8, 2019 – Multiple-choice questions...Essay questions
Thread Content
bg4.png【Daily Question】【AC Version for Static Equipment...Question 140】 August 08, 2019 Multiple-choice questions...Essay questions...........................................................................Reward rules: 3 Wealth points for participation, 2 Wealth points for getting one question right; the maximum reward is 10 Wealth points. No score will be given after two days, except during holidays. ...........................................................................1. Why is post-weld dehydrogenation necessary? ........................................................................... Answer: During welding, hydrogen from the electrode, flux, and moisture in the air is decomposed into atomic form at high temperatures and dissolves in the liquid metal. As the weld cools, the solubility of hydrogen in steel drops sharply; since the weld cools rapidly, hydrogen does not have time to escape and remains in the weld metal. After some time, it accumulates in the weld or at the fusion line. When they accumulate to a certain extent, under the influence of welding stresses, cold cracks, that is, delayed cracks, may occur in the weld or heat-affected zone. Therefore, it is necessary to preheat the welding rod first, and after welding, heat the weld to 200 degrees; the usual holding time for this heating process is 16 hours. This helps to reduce the cooling rate of the weld, allowing hydrogen to escape properly. This process is known as post-weld hydrogen removal treatment, and it is also why low-hydrogen welding rods should be used.
During welding, hydrogen from the electrode, flux, and moisture in the air is decomposed into atomic form at high temperatures and dissolves in the liquid metal. As the weld cools, the solubility of hydrogen in steel drops sharply; due to the rapid cooling of the weld, hydrogen does not have time to escape and remains in the weld metal. Over time, it accumulates in the weld or at the fusion line. When they accumulate to a certain extent, under the influence of welding stresses, cold cracks, that is, delayed cracks, may occur in the weld or heat-affected zone. Therefore, it is necessary to preheat the welding rod first, and after welding, heat the weld to 200 degrees; the usual holding time for this heating process is 16 hours. This helps to reduce the cooling rate of the weld, allowing hydrogen to escape properly. This process is known as post-weld hydrogen removal treatment, and it is also why low-hydrogen welding rods should be used.
During welding, hydrogen from the electrode, flux, and moisture in the air is decomposed into atomic form at high temperatures and dissolves in the liquid metal. As the weld cools, the solubility of hydrogen in steel drops sharply; due to the rapid cooling of the weld, hydrogen does not have time to escape and remains in the weld metal. Over time, it accumulates in the weld or at the fusion line. When they accumulate to a certain extent, under the influence of welding stresses, cold cracks, that is, delayed cracks, may occur in the weld or heat-affected zone. Therefore, it is necessary to preheat the welding rod first, and after welding, heat the weld to 200 degrees; the usual holding time for this heating process is 16 hours. This helps to reduce the cooling rate of the weld, allowing hydrogen to escape properly. This process is known as post-weld hydrogen removal treatment, and it is also why low-hydrogen welding rods should be used.
During welding, hydrogen from the electrode, flux, and moisture in the air is decomposed into atomic form at high temperatures and dissolves in the liquid metal. As the weld cools, the solubility of hydrogen in steel drops sharply; due to the rapid cooling of the weld, hydrogen does not have time to escape and remains in the weld metal. Over time, it accumulates in the weld or at the fusion line. When they accumulate to a certain extent, under the influence of welding stresses, cold cracks, that is, delayed cracks, may occur in the weld or heat-affected zone. Therefore, it is necessary to preheat the welding rod first, and after welding, heat the weld to 200 degrees; the usual holding time for this heating process is 16 hours. This helps to reduce the cooling rate of the weld, allowing hydrogen to escape properly. This process is known as post-weld hydrogen removal treatment, and it is also why low-hydrogen welding rods should be used.
During welding, hydrogen from the electrode, flux, and moisture in the air is decomposed into atomic form at high temperatures and dissolves in the liquid metal. As the weld cools, the solubility of hydrogen in steel drops sharply; due to the rapid cooling of the weld, hydrogen does not have time to escape and remains in the weld metal. Over time, it accumulates in the weld or at the fusion line. When they accumulate to a certain extent, under the influence of welding stresses, cold cracks, that is, delayed cracks, may occur in the weld or heat-affected zone. Therefore, it is necessary to preheat the welding rod first, and after welding, heat the weld to 200 degrees; the usual holding time for this heating process is 16 hours. This helps to reduce the cooling rate of the weld, allowing hydrogen to escape properly. This process is known as post-weld hydrogen removal treatment, and it is also why low-hydrogen welding rods should be used.
Answer: During welding, hydrogen from the electrode, flux, and moisture in the air is decomposed into atomic form at high temperatures and dissolves in the liquid metal. As the weld cools, the solubility of hydrogen in steel drops sharply; due to the rapid cooling of the weld, hydrogen does not have time to escape and remains in the weld metal. After some time, it accumulates in the weld or at the fusion line. When they accumulate to a certain extent, under the influence of welding stresses, cold cracks, that is, delayed cracks, may occur in the weld or heat-affected zone. Therefore, it is necessary to preheat the welding rod first, and after welding, heat the weld to 200 degrees; the usual holding time for this heating process is 16 hours. This helps to reduce the cooling rate of the weld, allowing hydrogen to escape properly. This process is known as post-weld hydrogen removal treatment, and it is also why low-hydrogen welding rods should be used.
During welding, hydrogen from the electrode, flux, and moisture in the air is decomposed into atomic form at high temperatures and dissolves in the liquid metal. As the weld cools, the solubility of hydrogen in steel drops sharply; due to the rapid cooling of the weld, hydrogen does not have time to escape and remains in the weld metal. Over time, it accumulates in the weld or at the fusion line. When they accumulate to a certain extent, under the influence of welding stresses, cold cracks, that is, delayed cracks, may occur in the weld or heat-affected zone. Therefore, it is necessary to preheat the welding rod first, and after welding, heat the weld to 200 degrees; the usual holding time for this heating process is 16 hours. This helps to reduce the cooling rate of the weld, allowing hydrogen to escape properly. This process is known as post-weld hydrogen removal treatment, and it is also why low-hydrogen welding rods should be used.
The purpose of hydrogen elimination treatment is to allow the metal in the weld pool to absorb hydrogen from the air during crystallization and cooling, thereby preventing the formation of delayed cracks that could lead to brittle fracture.
To allow the weld to cool slowly and ensure that the hydrogen atmosphere within the weld can escape fully.
Accelerate the escape of hydrogen from the weld joint to prevent cold cracks