Analysis of the Causes of Welding Cracks in NM450 Wear-resistant Steel

    
    Welding is one of the most widely used joining methods in manufacturing processes, and it is also a crucial step in the production and installation of wear-resistant steel. Welding not only provides the strength needed to construct a specific structure, but it also seals large areas or small crevices against water intrusion or chemical infiltration. However, welding is not without its challenges. In particular, one of the most common welding issues is welding cracks, which can lead to severe structural integrity degradation or even complete failure of the weld. In this article, we analyze the causes of welding cracks in NM450 wear-resistant steel.
    
    NM450 wear-resistant steel is a low alloy steel commonly used in constructions and ships building, mainly because of its good properties such as toughness, plasticity, weldability, and processability. The advantages of NM450 wear-resistant steel make it a desirable material for many applications that require high wear resistance. However, NM450 is susceptible to welding cracking, which can cause a variety of failures such as fracturing or stress corrosion cracking. Therefore, it is important to understand the causes of weld cracking in NM450 wear-resistant steel.
    
    Figure 1: Causes of welding cracks in NM450 wear-resistant steel
    1. Inadequate fusion: Inadequate fusion of the filler and base metals is one of the most common causes of weld crack formation in NM450 steel. When the fusion is insufficient, the weld is brittle and more prone to cracking, which could cause serious problems during the service life of the weld. To prevent this issue, a skilled welder should be sure to sufficiently heat the base and filler metals before welding, and the filler and base metallurgy should be closely matched.
    
    2. Poor weld bead edge profile: Poor weld bead edge profile is another potential cause of weld cracking in NM450 wear-resistant steel. If a bead has a smooth-transition edge that is too sharp, it can lead to higher levels of stress concentration, which increases the chances of weld crack formation. This can be avoided by ensuring a uniform weld edge profile by proper bead manipulation and by avoiding sudden angle changes or points of high accumulation of the weld deposit.
    
    3. Insufficient or excessive preheating temperatures: Preheating and postheating temperatures play an important role in welding NM450 wear-resistant steel. If the preheating temperature is too low, it can cause increased hardness and cold-formed crystalline defects or residual stresses, resulting in weld cracking. Conversely, if the preheating temperature is too high, there is an increased risk of intergranular cracking, which could eventually lead to weld cracking. Therefore, the preheating and postheating temperatures should be carefully controlled to ensure optimal weld properties.
    
    4. Excessive hardness of parent material: The hardness of the parent material is another factor that affects the weldability of NM450 wear-resistant steel. If the hardness of the parent material is excessive, it can result in increased levels of thermal stresses, which can cause weld cracking. For this reason, it is important to assess the hardness of the parent material before welding and adjust the welding parameters if necessary.
    
    In summary, there are several potential causes of weld cracking in NM450 wear-resistant steel. It is important for welders to be aware of these potential issues and the corresponding corrective measures to ensure that the welds are free from any cracking or other issues. By doing so, welding operators can ensure the reliability and durability of NM450 welds in various applications.

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