轨梁轧辊表面激光熔覆改性技术(5)

表11 送粉率对熔覆层表面的影响Tab.11 Influence of powder feeding rate on cladding surfacePowder feeding rate/(g·min-1) Macrophotograph Metallograph Brief description 20 images/BZ_221_755_714_930_1041.pngimages/BZ_221_1024_693_1436_1061.png40 images/BZ_221_746_1099_938_1448.pngMacroscopic scale: Poor lap flatness Microscopic scale: High dilution degree, locally visible base structure of base material images/BZ_221_1024_1078_1436_1470.png60 images/BZ_221_750_1498_935_1843.pngMacroscopic scale: Lap flatness Microscopic scale: Uniform structure images/BZ_221_1023_1487_1437_1855.pngMacroscopic scale: Poor lap flatness, Local bulge Microscopic scale: Uniform structure

4.4 扫描速度

按激光功率为3000 W，送分率为40 g/min，搭接率为30%，扫描速度分别为10、20、30 mm/s，进行单道熔覆实验，结果见表12。扫描速度为10 mm/s时，熔覆层表面略粗糙，且有氧化现象；扫描速度为20 mm/s 时，熔覆层表面光滑，且无杂纹裂纹；扫描速度为30 mm/s 时，熔覆层表面有气孔和裂纹。实验结果表明，扫描速度为20 mm/s 时，表面质量较好。

表12 扫描速度对熔覆层表面的影响Tab.12 Influence of scanning speed on cladding surfaceScanning speed/(mm·s-1) Macrophotograph Metallograph Brief description 10 images/BZ_221_746_2104_921_2441.pngimages/BZ_221_1044_2086_1421_2459.png20 images/BZ_221_729_2497_937_2833.pngMacroscopic scale: The surface is not smooth, there are raised, pores defects Microscopic scale: Large structure relatively images/BZ_221_1046_2476_1419_2854.png30 images/BZ_221_745_2883_922_3219.pngMacroscopic scale: smooth、 Microscopic scale: uniform structure images/BZ_221_1045_2871_1419_3231.pngMacroscopic scale: The surface has the stomata and the insufficient melts phenomenon Microscopic scale: Visible loose structure and inadequate feeding

综上可知，最佳激光熔覆工艺参数见表13，熔覆层与母材的物理指标见表14。通过激光熔覆工艺改性后，轨梁BD1 轧辊孔型内任何部位均没有粘钢的痕迹；激光熔覆层仍然保持着初始状态，没有明显的磨损失重；孔型立面的激光熔覆层表面形成了一层黑亮色的氧化膜，且氧化膜没有被磨损破坏的迹象。激光熔覆层没有发现任何剥蚀、脱落的现象。由于激光熔覆层仍然保留着良好的表面形态和孔型形状，经过激光熔覆后，过钢量由原来的不足1000 t可以提高到6000 t 以上。轨梁BD1 轧辊的耐磨性可提高4 倍左右；磨损的立面熔覆修补后，轧辊服役周期可达10 次；扣除激光熔覆成本，仍可将辊耗降低到原来五分之一以下，大幅度降低 DB1 轧辊的消耗。

表13 最佳激光熔覆工艺参数Tab.13 Optimum laser cladding parametersLaser power/ W Spot diameter/ mm Scanning speed/ (mm·s-1) Step size/ (mm·circle-1) Powder feeding rate/ (g·min-1) 3000～4000 5 12～20 2.5～3.2 30～40

表14 熔覆层与母材的物理指标Tab.14 Physical index of cladding surface and base metalThermal expansion coefficient/ (×10-6 ℃-1) Elastic modulus/ (×104 MPa) Friction coefficient 11～12 21～23 0.82～1.05

5 结论

1）用激光熔覆技术对轨梁BD1 轧辊表面进行处理，熔覆层表面形成了一层与轧材显著不同的金相组织，消除了粘钢现象。

2）激光熔覆改性的最佳参数为：激光功率3000～4000 W，扫描速度20 mm/s，送粉率30～40 g/min，搭接率30%。

3）经过激光熔覆改性后，轨梁BD1 轧辊表面熔覆层具有足够的抗压、抗冲击、抗机械疲劳和冷热疲劳能力，使用寿命成倍提高，轧辊下机车削减径量大幅减少，辊耗降低到改性前五分之一以下，提高了轧制生产效率，降低了轧辊辊耗。

[1] KIM Jaehyun, PARK Kee-cheol, KIM Do-nyun. Investigating the fluting defect in v-bending due to the yield-point phenomenon and its reduction via roller-leveling process[J]. Journal of materials processing technology, 2019, 270: 59-81.

[2] GAO Qiang, LIU Wen-jie, LI Dong, et al. Research and implementation of the roll position automatic adjustment system based on roller parameters prediction[J]. Journal of advanced manufacturing systems, 2019, 18(2): 273-292.

[3] JING Liu, TANG Chang-ke, SHAO Yi-min. An innovative dynamic model for vibration analysis of a flexible roller bearing[J]. Mechanism and machine theory, 2019, 135: 27-39.

[4] YU Yang, CHENG Jun-sheng. A roller bearing fault diagnosis method based on EMD energy entropy and ANN[J]. Journal of sound and vibration, 2006, 294(2): 269-277.

[5] 周旬, 王晓东, 苏长水, 等. 高铬铸钢轧辊的组织及其氧化行为[J]. 中国冶金, 2019, 29(5): 38-43. ZHOU Xun, WANG Xiao-dong, SU Chang-shui, et al. Microstructure and oxidation behavior of high Cr cast steel roll[J]. China metallurgy, 2019, 29(5): 38-43.

[6] 王建升, 唐明奇, 吕瑞丽, 等. 铸钢轧辊亚微米WC-4Co 电火花沉积涂层高温性能[J]. 焊接学报, 2017, 38(7): 49-53. WANG Jian-sheng, TANG Min-qi, LYU Rui-li, et al. High temperature performance of sub-micron WC-4Co EDM coating for cast steel rolls[J]. Transactions of the China Welding Institution, 2017, 38(7): 49-53.

文章来源：《中国表面工程》 网址: http://www.zgbmgc.cn/qikandaodu/2021/0708/647.html