微觀組織對車輪鋼力學性能和磨損性能的影響研究

燕青芝 車延婧 洪志遠

摘 要：車輪鋼和軌道鋼的微觀組織和力學性能對高鐵運行的安全性和服役壽命具有決定性影響。該工作采用淬回火和淬火霧冷兩種熱處理制度制備了具有等軸狀鐵素體和粒狀滲碳體的回火索氏體車輪鋼和片狀滲碳體分布在鐵素體中的索氏體車輪鋼。通過優化熱處理制度，兩種鋼的晶粒均在7級，屬于細晶組織。對兩種組織的鋼進行伸試驗，兩種鋼的拉伸強度大于900 Mpa，延伸率大于15%；由于淬回火車輪鋼中顆粒滲碳體的彌散強化作用，其強度比淬火霧冷的車輪鋼更高。夏比沖擊試驗表明，在室溫下淬火霧冷的車輪鋼沖擊吸收功高于淬回火車輪鋼，但隨著沖擊溫度的降低，淬火霧冷的車輪鋼沖擊功幅度下降幅，而淬回火鋼一直到-20℃韌性幾乎不降低。模擬高鐵載荷和時速500 km運行下輪軌接觸頻率，將兩種鋼與相同軌道鋼配副做滾動接觸疲勞試驗。結果表明：淬回火車輪鋼的疲勞壽命更長，裂紋的萌生主要發生在試樣的表面和亞表面夾雜物或應力集中處，在表面萌生的裂紋一般會沿一定的角度向內部擴展，然后沿平行于試樣表面進行擴展，最后從試樣上撕裂下來。裂紋擴展一般沿著夾雜物與基體界面進行；當夾雜物阻礙裂紋前進時，裂紋會繞過夾雜繼續擴展。在摩擦之后，車輪軌與軌道鋼的硬度都有1～2HRC的硬度下降，組織成分由于發生了再結晶及塑性變形下，條帶狀碳化物被碾碎等因素，使其與原始組織有了很大的不同。在硬度為34HRC左右時有最好的抗摩擦性能。

關鍵詞：高鐵車輪鋼 微觀組織 力學性能 滾動接觸疲勞

Abstract：The increasing of high-speed train speed puts forward higher requirements on wheel and rail materials. Microstructure and mechanical properties of high-speed wheel and rail steel have a great influence on the safety， comfort of trains. At high speed， the rolling contact fatigue of wheel steel problem is more prominent， becoming major injury problems of wheel material. According to the requirements of wheel and rail steel， this article developed heat treatment system for them and carried out the research work about the regular pattern on rolling contact fatigue crack initiation and expansion. By the experiments， the main research results obtained are as follows：（1）Two suitable heat treatment patterns for new high speed wheel and rail steel：①for wheel steel， one pattern is quenching at 860℃ and tempering at 530℃， the other is quenching at 860℃to about 650℃， then water spray cooling to ambient temperature；②for rail steel， one pattern is quenching at 820℃ and tempering at 580℃， the other is hold at 820℃， then water spray cooling to ambient temperature.（2）Finer grain both can be obtained by two different heat treatment patterns. Tempered sorbite is obtained by quenching and tempering， sorbite is obtained by quenching and water spray cooling for wheel steel and by water spray cooling for rail steel.（3）Comprehensive properties of heat treated wheel steel are better than as-received while steel， and the quenched and tempered wheel steel is better than quenched and water spray cooled while steel.（4）According to the results from rolling contact fatigue， the crack initiation occurs in surface and sub-surface where stress concentration at， and the crack usually extends along the interface between the inclusions and the matrix.（5）The hardness of wheel and rail steels decreases by 1～2 HRC after being rubbed， in the condition of recrystallization and plastic deformation， the composition become extremely different with the original structure because of the crush of banded carbide. As a conclusion， we can say that the material has the best anti friction performance when the hardness is about 34HRC.

Key Words：Wheel steel of high-speed train；Microstructure；Mechanical properties；Rolling contact fatigue

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