Common carbon steel weld on

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Carbon steel weld on is a key metal joining process, commonly used in various manufacturing industries, such as shipbuilding, automobile industry, construction industry, etc. This welding process involves melting and joining steel with a higher carbon content at the appropriate temperature, usually through methods such as arc welding, gas shielded welding, electrode welding, or wire welding. When welding carbon steel, the operator needs to adjust the welding parameters according to the characteristics and requirements of the material to ensure weld quality and connection strength. In addition, safety is an important factor that cannot be ignored during the welding process. Operators should strictly abide by safety regulations and wear appropriate protective equipment to reduce the risk of accidents.

1. Carbon steel welding techniques

When it comes to welding carbon steel, the process flow, applicable scenarios, advantages and disadvantages of different welding techniques can be described in more detail, as follows:

(1) Manual arc welding (SMAW):

Process flow: The welder uses a handheld electric welder to melt and fill the welding rod onto the workpiece using an electric arc to form a weld.

Applicable scenarios: Suitable for welding in various positions and angles, requiring high operating skills, suitable for outdoor use and situations where it is inconvenient to transport equipment.

Advantages: Suitable for outdoor environments, the equipment is simple and easy to carry, and the requirements for operators are low.

Disadvantages: The welding speed is relatively slow, the production efficiency is low, and the weld quality may be affected by the welder’s skills.

(2) Gas shielded welding (GTAW/TIG):

Process flow: The welder uses a hand-held TIG welding gun to protect the welding area with inert gas and manually controls the addition of welding wire or electrode.

Applicable scenarios: Suitable for occasions with high requirements on welding quality and appearance, such as aerospace, food processing, etc.

Advantages: The welding process is stable, the weld is beautiful and of high quality, and it is suitable for welding thin plates and stainless steel and other high alloy materials.

Disadvantages: It requires skilled welding skills and a high level of operation, and the welding speed is relatively slow.

(3) Gas metal shielded welding (GMAW/MIG):

Process flow: The welder uses a MIG welding gun to automatically or semi-automatically add welding wire through the gas-protected welding area.

Applicable scenarios: Suitable for mass production and high-speed welding situations, such as automobile manufacturing, metal structure manufacturing, etc.

Advantages: fast welding speed, high production efficiency, suitable for welding thick plates and large-sized workpieces.

Disadvantages: The cost of equipment and materials is high, and relatively complex equipment and control systems are required.

(4) Flux cored electrode welding (FCAW):

Process flow: The core material of the welding rod contains flux and filler metal. The welding rod melts under the arc and forms a weld. The flux produces gas protection and improves the quality of the weld.

Applicable scenarios: Suitable for welding operations in outdoor environments and strong wind environments.

Advantages: Fast welding speed, stable welding process, suitable for welding thicker plates.

Disadvantages: Welding slag and gas emissions may be produced during the welding process, which has higher environmental requirements.

(5) Electroslag welding (SAW):

Process flow: During welding, the space between the welding wire and the workpiece is protected by welding slag, and the welding wire is melted under the arc and filled into the weld.

Applicable scenarios: Suitable for welding thick plates and long workpieces, suitable for mass production and high-efficiency welding operations.

Advantages: fast welding speed, high welding quality, suitable for automated welding production lines with high production efficiency.

Disadvantages: It requires more complex equipment and control systems, and requires higher operator skills.

2. Welding of low carbon steel

(1) Weldability analysis

Low carbon steel contains less carbon and other alloying elements, has good plasticity and toughness, generally has no hardening tendency, is not prone to defects such as welding cracks, and has excellent welding performance.

When welding low carbon steel, special process measures such as preheating and post-weld heat treatment are generally not required.

Manual arc welding can be suitable for all-position welding when welding low carbon steel, and the welding process and operating technology are relatively simple and easy to master.

There is no need to choose special and complicated equipment, and there are no special requirements for welding power sources. Generally, AC and DC arc welding machines can weld.

(2) Welding materials

The welding materials used in fusion welding can be selected according to the principle of equal strength, that is, the strength of the weld is equal to or close to the strength of the base metal.

(3) Key points of welding process

If the base metal and welding materials are qualified, this kind of steel generally does not require preheating, maintaining interlayer temperature and post-heat treatment during welding, and excellent welded joints can be obtained. Corresponding measures can only be taken under the following circumstances:

When welding thick parts in a low temperature environment, the weldment should be preheated to prevent cold cracks;

Weldments with a thickness exceeding 50mm should undergo post-weld heat treatment to eliminate stress;

Electroslag welding parts should be normalized after welding to refine the HAZ grains.

3. Welding of medium carbon steel

Medium carbon steel is mainly used in the assembly of casting and forging blanks and repair welding work.

(1) Weldability

The heat-affected zone is prone to produce hardened structures with low plasticity. The higher the carbon content, the greater the thickness of the plate, and the greater the rigidity of the weldment. When the welding rod is improperly selected, cold cracks are likely to occur.

Weld metal is prone to thermal cracks.

Porosity is prone to occur in the weld area.

Medium carbon steel that has been quenched and tempered before welding will have a tempering and softening zone in the heat affected zone after welding, thus affecting the performance of the welded joint.

(2) Welding materials

Medium carbon steel mainly uses hand arc welding and gas welding. It is best to use low-hydrogen electrodes when hand arc welding, because low-hydrogen electrodes contain less diffusible hydrogen, have a certain desulfurization ability, have good plasticity and toughness of the deposited metal, and have high resistance to cold cracking and hot cracking. If the strength of the weld and the base metal is allowed to be unequal, welding rods with lower strength levels can be used. When the weldment is not allowed to be preheated, austenitic stainless steel electrode can be used because it has good plasticity and can avoid cracks.

(3) Key points of welding process

The welding groove should be opened into a U shape as much as possible to reduce the amount of melting of the weldment.

Preheat before welding, the preheating temperature is generally 150-250℃. When the carbon content is high, the plate thickness is large, or the structure is rigid, the preheating temperature can be increased to 250-400°C, and the heating range of local preheating is about 50 to 200mm on both sides of the weld.

When using low current multi-layer welding, especially when welding the first layer of weld, low current and slow speed welding should be used to reduce the proportion of the weldment melted into the weld metal (reduce the fusion ratio) and prevent thermal cracks.

Use alkaline welding rods. The electrode must be dried before welding at a drying temperature of 350-400°C for 2 hours.

Choose a reasonable assembly and welding sequence to improve stress distribution; use hammering welding methods to reduce welding residual stress and refine grains.

Cool slowly after welding. After welding, the weldment is placed in asbestos dust or placed in a furnace to cool slowly.

Post weld heat treatment. For weldments containing high carbon matrix, large thickness and high rigidity, tempering treatment at 600~650℃ is required after welding to eliminate stress.

4. Welding of high carbon steel

(1) Weldability analysis: The carbon content of high carbon steel is higher than that of medium carbon steel (>0.6%), so it is more likely to produce a brittle and hard martensite structure, with a greater tendency of brittle hardness and cold cracking sensitivity, so welding Such steels are generally not used in structures, and their welding is usually only used in repair work.

(2) Welding materials High carbon steel welded on can be hand arc welded and gas welded. The tensile strength of high carbon steel is mostly above 675Mpa. When the strength is high, J707 and J607 electrodes are generally used for hand arc welding. When the requirements are not high, J506 and J507 can be used, or low alloy steel with the same strength level as above can be used. Welding rod or filler metal. All welding materials should be of low hydrogen type to improve weld toughness and crack resistance.

(3) Key points of welding process

High carbon steel must be annealed before welding.

When using structural steel electrodes, preheating above 250-350℃ should be carried out before welding (if austenitic stainless steel electrodes are used, preheating is not required).

During the multi-layer welding process, the interlayer temperature should also be maintained at the same preheating temperature and slowly cooled after welding.

Usually, 650℃ high temperature tempering is required after welding to eliminate stress.

5. Main application areas of carbon steel

Welded carbon steel has a wide range of applications in various scenarios, including but not limited to the following major areas:

Construction and infrastructure construction: carbon steel welded on plays an important role in construction and infrastructure construction. It is commonly used for welding steel structures, bridges, building frames, stairs, railings, etc. These structures require welding to ensure strength and stability.

Automobile manufacturing: Automobile manufacturing requires a large amount of welding carbon steel process to join the body structure, chassis, wheels and other components. Welded carbon steel provides lightweighting and strength advantages that help improve a vehicle’s performance and durability.

Shipbuilding: In shipbuilding, welding carbon steel is one of the common processes used to join hulls, cabins, decks and other structural components. This welding ensures the ship’s structural strength and durability.

Oil and Gas Industry: The oil and gas industry requires extensive pipeline systems to transport and process crude oil, natural gas and other chemicals. Welding of carbon steel pipes is used to connect pipes, valves and other equipment to ensure the safe and reliable operation of the pipeline system.

Machinery Manufacturing: In the machinery manufacturing industry, carbon steel welded on is used to manufacture various mechanical parts, equipment and tools. For example, welded carbon steel is used to make pressure vessels, mechanical parts, machine tools, industrial robots, etc.

In the fields of industrial manufacturing and construction, carbon steel welding is a vital process. By joining steel with a higher carbon content through various welding techniques, we are able to create a variety of structural parts and components, providing a solid foundation for the development and progress of modern society.

Whether it is bridges in construction projects, car bodies in automobile manufacturing, hulls in shipbuilding, or mechanical parts in machinery manufacturing, carbon steel welded on plays an irreplaceable role. Various welding methods, such as manual arc welding, gas shielded welding, electrode welding and wire welding, provide us with a variety of choices to adapt to the needs of different scenarios.

However, no matter what welding method is used, safety and quality are always the most important factors in the welding process. Operators need to have rich welding experience and skills, strictly abide by operating procedures and safety requirements, and ensure a safe working environment and reliable welding quality.

In the future, with the continuous advancement of technology and the continuous improvement of processes, carbon steel welded on will continue to play an important role in providing continuous support for the development of various industries. Through unremitting efforts and continuous innovation, we will be able to utilize carbon steel welding technology more efficiently, promote the development of the manufacturing industry, and contribute to building a better future.