Application case overview
The valve stem is not only a moving part and a force-bearing part during the valve opening and closing process but also a sealing part. At the same time, it is impacted and corroded by the medium and also generates friction with the filler. The valve stem parts are prone to serious wear and tear, and there are problems such as scratches and strains.
Application background
The phosphorus removal injection valve stem in hot rolling mills is often repaired by electroplating. It has a short service life and can only be used for 4 months before it becomes worn and needs to be replaced. Each replacement takes 4 hours, seriously affecting production. It takes at least 1 year to use the laser to repair and strengthen the outer surface.
Cladding case
Material:
The cladding material adopts iron-based wear-resistant and corrosion-resistant alloy.
Process steps: Figure 3.33 Process steps diagram
Figure 3.33 Process steps diagram
Cladding process:
Figure 3.34 Cladding process using a linear nozzle
Metallographic examination:
According to GB/T 13298-2015, the metallographic examination after laser cladding is shown in Figure 3.35-1 below. As can be seen from the picture, there are no obvious defects. (Figure 3.35)
Figure 3.34 Cladding process using linear nozzle
Figure 3.35-1: 200X metallographic diagram, joint
Figure 3.35-2: 200X metallographic diagram, cladding layer
Hardness Testing:
The hardness test results are shown in Figure 3.36. According to the hardness test results, the average Rockwell hardness of the cladding layer is 60HRC, the average Vickers hardness of the heat-affected zone is 40HRC, and the average Vickers hardness of the base material is 37.3HRC.
Flaw detection:
The PT flaw detection results show no obvious defects, as shown in Figures 3.37 and 3.38 below.
Figure 3.36 Hardness curve (the positive abscissa position is the cladding and the negative position is the matrix, and the ordinate is the hardness value)
Figure 3.37 Appearance after cladding + machine addition
Figure 3.38 PT flaw detection result shows no defects
Fix name:
Valve stem reinforcement
Strengthening requirements:
Strengthen the surface of the parts to make the surface hardness reach above 56HRC without cracks or pore defects.
Picture during cladding process
Figure 1 after cladding is completed and machine added
Figure 2 after cladding is completed and machine added
