With the ongoing decline in the construction machinery market in recent years, sales of construction equipment have gradually decreased. As China's largest manufacturer of track-type bulldozers, Shantui has also been affected by this trend. To reduce production costs and improve economic benefits, a detailed analysis of the structural design and mechanical properties of bulldozers was conducted. Based on this, a rational selection of Q235B and Q345B materials was proposed through continuous research and testing.
By comparing the chemical composition and mechanical properties of Q235B and Q345B, it was found that Q345B can replace part of the Q235B in structural components of bulldozers. This replacement allows for a reduction in plate thickness while still meeting structural performance requirements, thereby reducing material usage and overall weight. This strategy helps lower costs and increase efficiency.
The chemical composition of both materials is shown in Table 1, and their mechanical properties are listed in Table 2. According to the company’s data from 2011, Table 3 outlines the annual consumption of Q235B and Q345B materials for 10,000 bulldozers.
In the welding process, the same parameters were used for both Q235B and Q345B. Although Q235B is a carbon steel and Q345B is a low-alloy structural steel, both exhibit good weldability. The manganese content differs, with Q235B having around 0.3%–0.8% Mn and Q345B having 1%–1.6% Mn. Tensile tests showed that Q345B has significantly higher tensile strength than Q235B. After welding, both materials passed the quality inspection standards (Q/STB12.606-2000).
Economic analysis revealed that using Q345B instead of Q235B can lead to cost savings. For example, a 10mm-thick Q345B plate can replace a 14mm-thick Q235B plate. Based on the price comparison in Table 5 and an annual output of 5,000 bulldozers, replacing half of the Q235B with Q345B could save approximately 3.87 million yuan annually, or about 775 yuan per bulldozer.
In conclusion, replacing Q235B with Q345B in certain structural parts not only meets design requirements but also reduces material costs. It is recommended that future product designs prioritize the use of Q345B, as it offers better performance and cost efficiency compared to Q235B.
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