What problems should I pay attention to when welding metals?

First of all, safety, especially eyes!

Welders must be equipped with safety equipment such as masks with suitable light filters, dry canvas overalls, gloves, rubber insulation, and white light glasses for slag removal. Prevent burns and fires from splashed metal or red-hot weldments. Prevent the harm of arc light radiation to the human body.

Prevent poisoning by certain harmful gases. When working at height, wear a seat belt and a helmet. When repairing and welding pressure vessels that have been filled with combustible substances, they can only be welded after they are disposed of according to the regulations, and welding accidents should be prevented.

Welding of load-bearing structures without reinforcement measures is not permitted. In welding in a humid environment, necessary measures should be taken to avoid electric shock accidents. In terms of welding operations:

Welding is carried out according to the process requirements of the drawing. The electrode should meet the design requirements and be dried according to the requirements. The form and size of the weld should meet the requirements of the drawings to ensure the quality of welding.

High-carbon steel welding and welding points and process lack of key points, such as Fu rough friends:

1. When the quality stool of high-carbon steel is greater, the hardening and crack sensitivity tendency after welding is greater, so the weldability is extremely poor and cannot be used to manufacture welded structures. It is often used to manufacture components and parts that require more hardness or wear resistance, and its welding work is mainly weld repair.

2. The tensile strength of high-carbon steel is mostly above 675MPa, so the commonly used electrode models are E7015 and E6015, and E5016 and E5015 electrodes can be selected when the requirements for the component structure are not high. In addition, chromium-nickel austenitic steel electrodes can also be used for welding.

3. High-carbon steel welding process:

1) Since high-carbon steel parts need to be heat-treated in order to obtain high hardness and wear resistance, they should be annealed before welding.

2) The weldment should be preheated before welding, and the preheating temperature is generally more than 250 350, and the interlayer temperature must be kept not lower than the preheating temperature during the welding process.

3) After welding, the weldment must be kept warm and cooled slowly, and immediately sent into the furnace for stress relief heat treatment at 650.

Summary. Hello, I am honored to answer for you: 1. Crack phenomenon, crack phenomenon has two kinds of hot cracks and cold cracks, hot cracks are the gaps that appear when the metal develops from a liquid state to a solid state, which generally appears in the middle position and is easy to find.

Cold crack is the fusion of the base metal produced when the weld metal is cooled or after a period of aging after welding, or the area where the base metal and the weld merge. 2. Undercut. Undercut refers to the pit at the edge of the weld, and there may be two reasons for the formation of undercut, one is caused by too large welding current or too fast speed or too long arc drawing, and the other is caused by the welding speed of submerged arc welding too fast or the unequal track of the welding machine.

3. Stomatae. The most common cause of porosity is that the edge of the groove has not been cleaned, leaving dirt or moisture. 4. Not welded through, not fused.

Failure to penetrate is when the root of the joint is not fully penetrated during welding. Unfused is a phenomenon of local unmelted bond between the weldment and the weld metal or weld layer. Lack of penetration and fusion are serious defects in the welding of metal materials, which will lead to the discontinuity of the weld, reduce the strength of the weld, and then cause cracks.

5. Slag inclusion. Slag inclusion refers to the slag left in the weld.

Hello, I am honored to answer for you: 1. Crack phenomenon, crack phenomenon has two kinds of hot cracks and cold cracks, hot cracks are the gaps that appear when the metal develops from a liquid state to a solid state, which generally appears in the middle position and is easy to find. Cold crack is the fusion of the base metal produced when the weld metal is cooled or after a period of aging after welding, or the area where the base metal and the weld merge.

2. Undercut. Undercut refers to the pit at the edge of the weld, and there may be two reasons for the formation of undercut, one is caused by excessive welding current or too fast speed of the bridge or too long arc, etc., and the other is caused by the welding speed of submerged arc welding too fast or the unequal track of the welding machine. 3. Stomatae.

The most common cause of porosity is that the edge of the groove has not been cleaned, leaving dirt or moisture. 4. Not welded through, not fused. Failure to penetrate is when the root of the joint is not fully penetrated during welding.

Lack of fusion is a phenomenon of local unmelted bond between the weldment and the weld metal or the weld layer. Lack of penetration and fusion is a serious defect in the welding of metal materials, which will lead to the intermittent weld, reduce the strength of the weld, and then cause cracks. 5. Slag inclusion.

Slag inclusion refers to the slag left in the weld.

Relevant information: 1. Carry out activities in strict accordance with the welding process steps, reduce the low welding stress of Zheng Lu, carefully control the welding process parameter elements, and choose the best welding process parameters. 2. When welding, it is necessary to select the appropriate welding current and transportation method, and observe and control the angle and arc length of the welding rod in real time.

3. Select the appropriate welding current and speed, clean up the dirt of the interface during welding, and keep the welding materials in accordance with the regulations. To sum up, in the process of metal material welding, in order to ensure the welding quality of metal materials and improve the performance of materials, it is necessary to have strict requirements for metal welding technology, and at the same time operate in accordance with the above common problems and precautions to avoid welding problems.

The matters that should be paid attention to when welding include the welding speed, the length of the arc, the order to be considered in the selection of welding wire, and the key points of welding wire selection.

1. Welding speed.

The appropriate welding speed is based on the diameter of the welding rod, the type of coating, the welding current, the heat capacity of the welded object, the beginning of the structure and other conditions, and there are corresponding changes, and the standard cannot be stipulated. Maintain the right welding speed, and the slag can cover the molten pool well.

All kinds of impurities and gases in the molten pool have sufficient time to float out, so as to avoid the formation of slag inclusions and porosity of the weld. If the speed of the rod is too fast during welding, the shrinkage stress will increase when the welding part is cooled, causing cracks in the weld.

Second, the length of the arc.

The length of the arc is related to the type of electrode coating and the thickness of the coating. However, short arcs should be taken as much as possible, especially low-hydrogen electrodes. Long arcs can cause stomatosis.

The short arc can avoid harmful gases such as O2 and N2 in the atmosphere from invading the weld metal and forming undesirable impurities such as oxides and affecting the quality of the weld.

Third, the order to be considered in the selection of ruler fluttering ear welding wire.

1. Select the welding wire according to the steel type of the welded structureFor carbon steel and low-alloy high-strength steel, the welding wire that meets the mechanical property requirements is mainly selected according to the principle of "equal strength matching".

2. According to the quality requirements of the welded parts (especially the impact toughness), the selection of welding wire is related to the welding conditions, groove shape, shielding gas mixing ratio and other process conditions, and the welding materials that achieve large welding efficiency and reduce welding costs should be selected under the premise of ensuring the performance of welded joints.

3. Select the diameter of the welding wire according to the on-site welding position corresponding to the thickness of the welded workpiece, determine the current value used, refer to the product introduction information and use experience of each manufacturer, and select the welding wire grade suitable for the welding position and current used.

Fourth, the key points of welding wire selection.

The selection of welding wire should be based on the type of steel to be welded, the quality requirements of the welded parts, the welding construction conditions (plate thickness, groove shape, welding position, welding conditions, post-welding heat treatment and welding operation waiting), cost, etc.

1. Before welding aluminum alloy, the surface of the aluminum alloy should be cleaned first to ensure that there is no dust, oil and other dirt on the surface.

2. The specific heat capacity and thermal conductivity of aluminum alloy are twice that of low-alloy steel, so in the process of welding aluminum alloy, a large amount of heat will be transmitted to the metal in a short time, so when welding aluminum alloy, we should use energy with high power and concentrated energy.

3. When the aluminum alloy changes from solid to liquid, the color will not change significantly, which causes the inconvenience of the welding torch to prepare for the land, so the aluminum alloy welding operator is required to master the skilled welding skills and be able to judge the heating temperature of the aluminum alloy through the change of the surface of the molten pool.