Development of High Strength Steel Designed for Carbonitriding with High Nitrogen Content to Be Used for Automatic Transmission Gears
来源期刊：材料热处理学报2004年第5期
论文作者：Youichi Watanabe
关键词：Carbonitriding; Nitrogen; Shot peening; Contact fatigue strength; Pitting; Gear;
摘 要：To downsize and lighten automatic transmission components, the gears installed must be strengthened in terms of pitting endurance and/or wear resistance. The most important metallurgical factor affecting fractures is well known to be resistance to softening when steel is tempered at approximately 573 K. Carbonitriding with a high anount of nitrogen is a very effective production technique because nitrogen increases the resistance during tempering. However, structural anomalies begin to appear in the surface layer when the nitrogen content exceeds 0.6 mass% in the chromium steel generally used. To address this, we have developed new high-strength chromium steel with an optimized chemical composition that effectively inhibits anomalies even when carbonitriding with a nitrogen content of more than 0.6 mass%.We performed a drivetrain durability test on an automatic transmission component designed to have excellent contact fatigue strength and a tooth root bending impact and fatigue strength. We found that the developed steel that was carbonitrided with a content of about 0.9 mass%, and then shot peened hard, has a pitting life of roughly 4.5 times that of conventionally manufactured steel.
Youichi Watanabe1
(1.Nissan Motor Co., Ltd., 6-1, Daikoku-cho, Tsurumi-ku, Yokohama, Japan)
摘要:To downsize and lighten automatic transmission components, the gears installed must be strengthened in terms of pitting endurance and/or wear resistance. The most important metallurgical factor affecting fractures is well known to be resistance to softening when steel is tempered at approximately 573 K. Carbonitriding with a high anount of nitrogen is a very effective production technique because nitrogen increases the resistance during tempering. However, structural anomalies begin to appear in the surface layer when the nitrogen content exceeds 0.6 mass% in the chromium steel generally used. To address this, we have developed new high-strength chromium steel with an optimized chemical composition that effectively inhibits anomalies even when carbonitriding with a nitrogen content of more than 0.6 mass%.We performed a drivetrain durability test on an automatic transmission component designed to have excellent contact fatigue strength and a tooth root bending impact and fatigue strength. We found that the developed steel that was carbonitrided with a content of about 0.9 mass%, and then shot peened hard, has a pitting life of roughly 4.5 times that of conventionally manufactured steel.
关键词:Carbonitriding; Nitrogen; Shot peening; Contact fatigue strength; Pitting; Gear;
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