In practice, we can know that there are many reasons for the cracking of the stainless steel clad head, so what are the main reasons? Let’s take a look with everyone today!
1. The effect of explosive recombination
The location of the stainless steel multi-layer cracks is concentrated on the base material of the head near the circumferential seam of the head. The head is made of low-alloy steel + austenitic stainless steel composite plate. The composite plate will produce large residual stress and plastic deformation at the joint during the explosive cladding process, but the gold near the longitudinal weld from the cylinder lining Based on the analysis of the sampling results of phase, hardness and ferrite content, explosive cladding did not have a significant impact on the surface of the stainless steel clad layer.
2. The influence of head forming and heat treatment
The head forming method can generally be divided into cold forming and hot forming. From the hardness, ferrite content, and metallographic structure of the head, it can be known that the glue tank composite plate head adopts the cold forming method. In the process of pressing the flaps of the head, the plastic deformation of the straight side of the head is the most serious, and the metastable austenite may produce higher hardness strain-induced martensite during the plastic deformation process. Sampling results of ferrite content show that the ferrite content far away from the edge of the head shows a gradually decreasing trend. The ferrite content of the crack existing part is about 20%, indicating that there is a magnetic phase structure in this part, and the metallographic analysis shows that there is deformation-induced martensite in this part. The ferrite content affects the ability of austenitic stainless steel to resist intergranular corrosion.
3. Stress analysis
After the explosive composite plate is manufactured, the hardness, shear strength, and tensile strength of the bonding zone will all increase. During the forming process of the head, due to the different deformation rates and linear expansion coefficients of the base material and the composite material, the cold and hot processing will generate higher stress in the deformed part, and at the same time superimpose the influence of the edge stress of the head, in the straight edge section of the head The large curvature bending section of the head will generate greater stress, especially in the bonding area of the clad steel plate. As a result, the surface stress of the lining increases, the strength increases, and the hardness value increases. The hardness of the part where the headlining crack exists is basically about 300HB, indicating that this part is a high-stress area.
The cold-formed stainless steel headlining produces a deformation-induced martensite structure due to plastic deformation and superimposes the precipitation phases that may exist in the subsequent welding and heat treatment processes, which weakens the grain boundary corrosion resistance of austenitic stainless steel. In addition, the storage medium can react to generate a trace amount of hydrofluoric acid, which causes the head of the composite plate to undergo intergranular stress corrosion cracking after the glue tank has been in service for a period of time. In order to prevent the occurrence of such cracks, appropriate methods should be selected when the head is formed, and reasonable heat treatment should be carried out in time, and the equipment should be strictly tested during the acceptance of the equipment.
Baoji Taicheng Clad Metal Materials Co., Ltd is a professional stainless steel clad steel head factory, which can provide you with customized stainless steel clad steel head. If you have any questions about the head, please feel free to contact us. Professional customer service staff will serve you online 24 hours a day!
