Failure analysis of tower axle in the wet drawing machine

Applied Mechanics and Materials Vols. 395-396
783

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Fig. 3 Microstructure SEM photos of the tower axle fracture 
（a）morphology of source area of crack;（b）morphology of the first crack propagation region ;（c）morphology of the 
second crack propagation region ;
（d）transient fault 
Analysis of 40Cr steel quenched and tempering treatment 
According to the data [4,5], process for tempering heat treatment is quenching and high temperature 
tempering.
As shown in Fig. 4 is process diagram of 40Cr [6]. 
air cooling
air cooling
air cooling
air cooling
6 2 0
℃
5 -6 h
3 -4 h
oil cooling
oil cooling
oil cooling
oil cooling
T
/
℃
t/h
8 6 0
℃
Fig. 4 Process diagram of the quenched and tempered treatment for 40Cr 
The diameter size of tower axle is Φ 60 mm during heat treatment. In order to ensure the same 
sample specification, they are cut into 10*10*10 (mm
3
). This sampling plan is shown in Fig. 5. A 
strip is cut along diameter direction. It is cut into two parts along the middle. One part is divided 
into three thirds in order that the cross-sectional microstructure is observed. The other part of the 
designation is also divided into three parts according to the dotted line. Hardness of its edge, 
subcenter and the center are measured. 
Fig. 5 Sampling scheme of tower axle 
（a）physical sample figure;（b）sampling schematic diagram 
Microstructure analysis
After tempering treatment, 40Cr steel has the good comprehensive mechanical properties, low 
temperature impact toughness, low notch sensitivity and good hardenability. High fatigue strength 
can be obtained when it is oil cooling. 40Cr steel is one of the most widely used steel and 
commonly used to manufacture shaft, gear and other parts [7].