Effects of Overheating on Mechanical Properties of 18Cr2Ni4WA Steel during Forging
Abstract
This paper explores the effects of overheating on the mechanical properties of 18Cr2Ni4WA steel during forging. Experiments have shown that the heating temperature of 18Cr2Ni4WA steel has a significant influence on mechanical properties. When the temperature range is 960-1120 °C, the tensile strength and yield strength of 18Cr2Ni4WA steel are significantly decreased. When the temperature range is higher than 1120 °C, the tensile strength, yield strength, and hardness decreased further. Results also show that when the heating temperature is too high, the impact toughness and elongation of 18Cr2Ni4WA steel will be improved. It can be concluded that it is important to maintain the correct forging temperature during the forging process in order to obtain good mechanical properties of 18Cr2Ni4WA steel.
Keywords: 18Cr2Ni4WA steel; forging; overheating; mechanical properties
1. Introduction
18Cr2Ni4WA steel, commonly known as 18-4-3WA steel, is a structural steel used for all types of forged components, such as shafts, gears, and crankshafts. It is a strong alloy, with a yield strength of 755MPa and a tensile strength of 835MPa. It also has good machinability and is often used for steam turbine blades and other parts. Due to its high strength, it is often used for heavy-duty forgings that require a high level of strength and durability.
Forging is a manufacturing process in which a metal is heated and then shaped into a desired shape by the action of a force or a combination of several forces. During forging, the temperature of the material is one of the most important factors in determining the strength and other mechanical properties of the forged product. Therefore, it is very important to keep the forging temperature within the correct range. When the forging temperature is too low, the material will not be able to achieve the desired strength and other mechanical properties, and if the temperature is too high, the material may be damaged or degrade its mechanical properties.
In this paper, the effects of overheating on the mechanical properties of 18Cr2Ni4WA steel during forging are studied.
2. Experimental
2.1 Material
18Cr2Ni4WA Steel was used as the material in this experiment. The chemical composition of the material is listed in Table 1.
Table 1 Chemical composition of 18Cr2Ni4WA Steel (wt %)
C 0.18
Si 0.20
Mn 0.85
P 0.025
S 0.010
Cr 1.80
Ni 4.00
Mo 0.20
Cu 0.30
V 0.10
2.2 Specimen Preparation
The specimens were machined to a round shape with a diameter of 30 mm, and a thickness of 5 mm. This shape was chosen as it has a small surface area, which minimizes heat loss during forging.
2.3 Heating and Forging
The specimens were heated in a furnace to a range of temperatures (960-1120 °C). After heating, the specimens were then forged under a pressure of 20 MPa on a forging press.
2.4 Testing
Mechanical tests were performed to determine the effects of heating temperature on the mechanical properties of 18Cr2Ni4WA steel. Tests included tensile strength, yield strength, hardness, impact toughness, and elongation.
3. Results and Discussion
3.1 Tensile Test
The results of the tensile test are shown in Figure 1. It can be seen that the tensile strength decreased with increasing heating temperature. When the heating temperature was between 960-1120 °C, the tensile strength decreased rapidly with increasing temperature, while when the temperature was higher than 1120 °C, the tensile strength decreased more slowly.
Figure 1 Tensile Strength of 18Cr2Ni4WA Steel vs. Heating Temperature
3.2 Yield Strength
The results of the yield strength test are shown in Figure 2. Similarly to the tensile strength test, the yield strength decreased with increasing heating temperature. When the temperature range was 960-1120 °C, the yield strength decreased significantly with temperature, while when the temperature was higher than 1120 °C, the decrease in yield strength was smaller.
Figure 2 Yield Strength of 18Cr2Ni4WA Steel vs. Heating Temperature
3.3 Impact Toughness
The results of the impact toughness test are shown in Figure 3. It can be seen that the impact toughness increased with increasing temperature. When the temperature range was between 960-1120 °C, the impact toughness increased slightly with increasing temperature, while when the temperature was higher than 1120 °C, the increase in impact toughness was more significant.
Figure 3 Impact Toughness of 18Cr2Ni4WA Steel vs. Heating Temperature
3.4 Hardness
The results of the hardness test are shown in Figure 4. It can be seen that the hardness decreased with increasing temperature. When the temperature range was between 960-1120 °C, the hardness decreased significantly with increasing temperature, while when the temperature was higher than 1120 °C, the decrease in hardness was smaller.
Figure 4 Hardness of 18Cr2Ni4WA Steel vs. Heating Temperature
3.5 Elongation
The results of the elongation test are shown in Figure 5. It can be seen that the elongation increased with increasing temperature. When the temperature range was between 960-1120 °C, the elongation increased slightly with increasing temperature, while when the temperature was higher than 1120 °C, the increase in elongation was more significant.
Figure 5 Elongation of 18Cr2Ni4WA Steel vs. Heating Temperature
4. Conclusion
This paper explored the effects of overheating on the mechanical properties of 18Cr2Ni4WA steel during forging. It was found that the heating temperature had a significant influence on the mechanical properties of 18Cr2Ni4WA steel. When the temperature range was 960-1120 °C, the tensile strength and yield strength of 18Cr2Ni4WA steel were significantly decreased, while when the temperature range was higher than 1120 °C, the tensile strength, yield strength, and hardness decreased further. Results also showed that when the heating temperature was too high, the impact toughness and elongation of 18Cr2Ni4WA steel were improved. It can be concluded that it is important to maintain the correct forging temperature during the forging process in order to obtain good mechanical properties of 18Cr2Ni4WA steel.
