Basic Principles for Welding Material Selection

1

Consider the physical properties, mechanical properties, and chemical composition of welding materials.

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Welding of structural steel typically involves considering the principle of equal strength, selecting welding materials that meet the mechanical property requirements of the joint.

For dissimilar steel weld joints between low-carbon steel and low-alloy steel, it is generally advisable to use welding materials that correspond to the lower strength grade of the steel.

(3) When welding heat-resistant steel and stainless steel, in addition to considering strength, it is also essential to ensure that the main chemical composition of the weld metal is similar to that of the base material.

When the chemical composition of the base material contains a high concentration of harmful impurities such as carbon, sulfur, or phosphorus, it is advisable to select welding materials with strong crack resistance, such as low hydrogen welding materials.

2

Consider the working conditions and performance of the weldments.

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Weldments must meet high requirements for impact toughness and plasticity in addition to tensile and yield strengths when subjected to dynamic and impact loads. Low-hydrogen welding materials should be chosen in such cases.

(2) When welding parts in corrosive mediums, it is essential to identify the type of medium, its concentration, operating temperature, and the type of corrosion (common corrosion, intergranular corrosion, stress corrosion, etc.), in order to select the appropriate stainless steel welding material.

(3) When weldments operate under wear conditions, it is crucial to differentiate between general wear and impact wear, intermetallic wear versus abrasive wear, wear at room temperature versus at high temperatures. Additionally, consider if the operation is in a corrosive medium to select the appropriate surfacing welding material.

(4) Weldments operating at low or high temperatures should be selected with welding materials that ensure mechanical properties at those temperatures.

3

Consider the complexity and structural characteristics of the welding parts, as well as the types of welding joints.

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Complex-shaped or thick weldments are prone to cracking due to the high internal stress generated by the shrinkage of the weld metal during cooling. As a result, weld materials with good crack resistance, such as low-hydrogen welding rods and high-toughness welding rods, must be used.

For certain joints with smaller bevels or joints requiring strict root penetration control, welding materials with greater penetration or deep melting capabilities should be selected.

(3) When certain welding areas are difficult to clean due to restrictions, consider using welding materials that are insensitive to rust, scale, and oil stains, such as acid-core rods, to prevent defects like porosity.

4

Consider the spatial position of the welds

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Certain welding materials are suitable only for welding at specific positions, with poor results at other positions. Others can be used for welding at various positions, and the choice should consider the characteristics of the welding position.

5

Consider welding work conditions and operating environment

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In the absence of a DC welding machine, AC/DC dual-purpose welding material should be selected.

(2) Some steel types, such as pearlitic heat-resistant steel, require stress-relieving heat treatment after welding. However, if this is not possible due to equipment or structural limitations, alternative welding materials with a different chemical composition from the base metal should be used (e.g., austenitic stainless steel welding material), which would eliminate the need for post-weld heat treatment.

(3) Welding materials should be selected rationally based on the construction site conditions, such as field operations and welding work environments.

(4) In situations where both acidic and alkaline welding rods are sufficient, due to the higher technical requirements and preparation for alkaline welding rods, it is advisable to opt for acidic welding rods as much as possible.

6

Consider the economic benefits of welding.

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Under the premise of ensuring performance, we strive to choose welding materials with high cost-performance.

(2) For primary and secondary welds with varying performance requirements, different welding materials can be used; do not overly pursue the comprehensive performance of welding materials.

7

Consider Welding Efficiency

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For structures with high welding workloads, it is advisable to opt for rate-welding materials, such as welding wires, iron powder welding rods, and high-efficiency stainless steel welding rods, whenever conditions permit.