With the continuous downturn in the construction machinery market in recent years, sales of construction equipment have declined. As China's largest crawler bulldozer manufacturer, Shantui has also been affected by this trend. To reduce production costs and improve economic efficiency, a comprehensive analysis of material selection was conducted, focusing on the structural design and mechanical properties of bulldozers. The study concluded that Q345B steel could be used to replace part of the Q235B steel in structural components, allowing for thinner plates while maintaining performance, thus reducing material usage and overall weight.
Q235B and Q345B are both commonly used in track-type bulldozers. While Q235B is a carbon steel with lower tensile strength, Q345B is a low-alloy structural steel offering better mechanical properties. By replacing Q235B with Q345B, it is possible to reduce the thickness of the steel plates without compromising structural integrity. This change not only helps maintain mechanical performance but also leads to cost savings through reduced material consumption.
The chemical composition and mechanical properties of the two materials were compared, as shown in Tables 1 and 2. Table 3 illustrates the annual material consumption for 10,000 bulldozers using these steels. In welding tests, both materials followed the same welding parameters, ensuring consistent quality. Despite differences in manganese content, both materials exhibited good weldability, and the resulting welds met the company’s quality standards (Q/STB12.606-2000).
Using Q345B instead of Q235B allows for a reduction in plate thickness, which translates into significant cost savings. For example, a 10mm thick Q345B plate can replace a 14mm thick Q235B plate. Based on material prices in Table 5 and an annual production of 5,000 bulldozers, replacing half of the Q235B with Q345B results in an annual cost saving of approximately 3.87 million yuan, or about 775 yuan per bulldozer.
In conclusion, replacing Q235B with Q345B in certain structural parts of bulldozers is a viable strategy to reduce costs while maintaining performance. This approach requires adjustments in design, such as modifying plate thickness and welding grooves, as well as some tooling changes. It is recommended that future product designs prioritize the use of Q345B over Q235B, as it offers better value and supports long-term cost efficiency.
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