What are the analysis and prevention of typical defects in marine anchors?

(1) Typical defects

Typical defects found in marine anchors during the inspection process include: the anchor rod or anchor head breaks or has cracks or major deformation after falling; after the magnetic particle inspection of the tensile test, pores, cracks, etc. are found; inclusions near the riser; anchor weight, size, The thickness does not meet the standard; the gaps between various parts of the anchor exceed the standard; there are hollow parts inside the cast anchor; accidents of anchor running or breaking occurred on the ship. As shown in Figure 4.

(2) Analysis and prevention of fracture of anchor components after falling

After the drop test and knock test, if the anchor component is broken or incomplete, the component should be rejected and no repairs are allowed. Innate defects on the surface of the anchor component can cause fracture. The essential reason for the occurrence of fractures, cracks, and major deformation is that the entire pouring process of the anchor component deviates from the process requirements. Steps in the pouring process that deviate from the process requirements should be thoroughly investigated and promptly corrected.

(3) Analysis and prevention of stomata

Porosity is a common defect in the casting process. It may exist singly or in aggregate, with different sizes and shapes, and the hole walls are smooth.

The anchor component is affected by many factors such as air flow and temperature during the casting process, and the internal and surface layers will be damaged. After conducting surface non-destructive testing on scrap ship anchors, it was found that 78% of the pores were intrusive, 13% were entangled, and 9% were precipitated. The preventive measures for intrusive pores are to strictly control the quality of the molding sand, ensure that the drying process of the molding sand is sufficient, and discharge a large amount of gas.Measures to prevent entangled pores include adjusting the exhaust function of anchor components and selecting raw materials with appropriate elements to avoid corrosion and prevent the formation of oxides or high hydrogen content that may affect the overall quality. The preventive measures for precipitation-type pore defects are to regulate the pressure difference between the inside and outside during the casting process of the anchor component to control the precipitation of gas inside the mold shell.

(4) Analysis and prevention of inclusions at risers and other parts

Cracks are found on the surface of the anchor parts, and molding sand or non-metallic inclusions are often found inside after polishing. From the perspective of chemical composition, non-metals include sulfides, oxides, nitrides, etc. , which are important causes of cracks. They mainly come from two aspects: one is endogenous inclusions, usually with small particles and even distribution. ; The second is foreign inclusions, which are generally larger in size, irregular in shape, and unevenly distributed.

Improperly configured ladle drains can also be an important factor leading to inclusions. The flow rate of a 40 mm diameter drain is only about 65% of the flow rate of a 50 mm diameter drain. During the pouring process, the temperature of the molten steel will drop by 2℃ every minute, and the pouring needs to be completed within 30 minutes. If a small-diameter nozzle is used, the pouring time will be increased by 20 minutes, the temperature of the molten steel will be reduced by 40℃, the fluidity will be reduced, and part of the molten steel will not flow to the riser, resulting in ladle slag near the riser.

The correctness of the riser feed design of the anchor component is also an important factor in determining the quality of the riser. The solidification time of the fed part should be shorter than the solidification time of the riser. At the same time, sufficient feeding fluid must be ensured to meet the feeding needs of the anchor component.

(5) Analysis and prevention of anchor accidents

Anchor accidents often occur on ships at anchor. The main reasons include poor anchor claw grip due to poor bottom quality, excessive impact on the anchored ship due to increased wind, waves and sway, improper anchoring method by the crew, and the length of the anchor chain. Insufficient or entangled, and insufficient weight of the anchor itself. The phenomenon of anchor walking is very dangerous. In severe cases, it may cause the anchored vessel to run aground, run aground, collide or even capsize. Therefore, improving the anchoring techniques and skills of the crew and strengthening the sense of responsibility of the crew on duty to watch the marine anchor can effectively and timely avoid anchoring. In addition, choosing to anchor in a sheltered place with good bottom, appropriate water depth, is also an effective method to prevent anchor walking.