卫生纸机用钢制扬克烘缸的喷涂

The Spraying of Steel Yankee Cylinders Used in Tissue Machine

在生活用纸抄造领域，由于钢在韧性、热传导和安全性方面与铸铁相比有较大的优势，钢制扬克烘缸正逐渐替代铸铁扬克烘缸。钢制扬克烘缸缸面喷涂硬质合金涂层，表面比铸铁更加坚硬，涂层能提高纸品品质，延长烘缸寿命，延长维护周期，促进化学涂布和起皱工艺的完成。钢制扬克烘缸不会在使用寿命期限内，因为壁厚的变薄或者金属涂层的脱落而降低等级。山东信和造纸工程股份有限公司已成功制造φ3000mm及φ3660mm钢制扬克烘缸，现已具备生产φ6000mm×5000mm钢制扬克烘缸的能力，喷涂由意大利RIF公司实施。

In the manufacture of tissue paper, the cast iron Yankee dryers are being replaced by the dryers made from steel gradually, because the latter has obvious advantages in toughness, heat conduction and safety. The surface of steel Yankee dryer cylinder sprayed with cemented carbide coating is harder than the surface of cast iron, which can improve the quality of paper products, extend the life of the dryer and the maintenance cycle, and help to complete chemical coating and wrinkling process. The grade of steel Yankee dryer cylinder would not be reduced with the decrease in thickness or thinning of a metallic coating. Shandong Xinhe has developed and produced the steel Yankee dryer cylinder with φ30 0 0m m and Φ3660mm. Nowadays, Xinhe has had the ability to produce the steel Yankee dryer cylinder with size of Φ6000mm×5000mm, with the spraying implemented by RIF corporation in Italy.

我们选用的扬克烘缸钢板为特殊的中强钢板，能够更好地承受喷砂糙化表面，通过增加表面自由能而激活表面，同时增大了喷涂微粒粘附的表面面积。热喷涂原理如图1。

The steel used in the Yankee dryer cylinder produced by Xinhe is medium-strength steel plate, which can better endure sand blasting roughening surface, activate the surface by increasing surface free energy, and also enlarge the surface area of spraying particles adhered. The principle of thermal spray can be seen in Figure 1.

图1  热喷涂原理示意

涂层材料：可以是线状或粘末状，这取决于热喷涂工艺类型。钢制扬克烘缸的涂层要具有如下特点：（1）表面高强度，必须达到55HRC以上；（2）耐磨，使用寿命长；（3）热传导和抗腐蚀能力强；（4）涂层致密，表面光滑；（5）涂层颗粒结合强度好，不易脱落（随烘缸变形）；（6）材料均匀一致，化学惰性。

Coating material: It can be linear or sticky which depends on the techniques of thermal spray. The coating material of the steel Yankee dryer cylinder is featured by: (1) high surface strength, over 55HRC; (2) wear resistant and long service life; (3) good heat conduction and corrosion resistance; (4) dense and smooth coating; (5) good bonding strength and not easy to fall off; (6) uniform material and chemically inert.

热喷涂工艺：扬克烘缸目前采用热喷涂涂层工艺为电弧线材喷涂，是将各自带有正负电荷，通常相同化学成分的两条金属线接触产生电弧，瞬间产生高热将金属线材尖端熔化，压缩空气将熔融的喷涂材料雾化，然后加速喷射到缸体表面，喷涂的速度通过调节适当的线材进给量进行调速，因此才能保持电弧恒定（见图2）。目前，扬克烘缸需要的涂层厚度一般为0.75mm左右，粗糙度：0.3～0.6μm，高的硬度可以耐受更加坚硬的刮刀操作，同时也提高了成纸的柔软度，使烘缸具有更广阔的操作提升空间。

Techniques of thermal spray: The Yankee dryer with thermal spray coating process is wire arc spraying. In the process, two metal wires with positive and negative charges and usually the same

chemical composition are used to produce the arc, which can instantly generate heat to melt the metal wire tip, and the compressed air can make the spray material melting atomization, then accelerate spray into the cylinder surface. The spraying speed of wire can be control by adjusting the wire feed speed appropriately, so a constant arc can be maintained (Figure 2). At present, the Yankee dryer, with coating thickness of about 0.75mm and roughness of 0.3 ~ 0.6μm, can endure harder scraper operation and improve the softness of the paper, thus making a wider space for the operation and promotion of dryers. Steel dryer cylinder must be pre-grinded before spraying, and the appropriate camber should be calculated according to the structure of Yankee and vacuum roller.

图2  电弧喷涂工艺原理

钢制烘缸在喷涂前必须进行预研磨，根据扬克烘缸和真空托辊的结构计算出合适的中高。

钢制扬克烘缸喷涂的具体流程，见图3。

The specific process of steel Yankee dryer spraying is shown in Figure 3.

图3  喷涂流程

喷涂以后的钢制扬克烘缸，具有高的热传导性，与铸铁扬克缸相比可以节约30%的汽耗。

The Yankee dryer cylinder after spraying has high thermal conductivity, thus saving 30% steam consumption compared with cast iron cylinder.

涂层测量：除了涂层特性非常重要之外，还有一些性能相对容易测试，并且具备标准的质量控制检测方法，它们是：（1）目测；（2）涂层厚度的测量；（3）表面粗糙度测量。如果有必要的话，可以在相同的时间和相同的条件下喷涂试验样板，能够及时对涂层进行测试，以确定涂层质量的其他性能：为精确测定涂层厚度、孔隙率和结构，以及未熔化颗粒、氧化夹杂物的微观结构，对涂层进行横向截面测试。还有用一种特殊的粘结剂及试验设备进行结合强度测定；除此之外，各种元素分析方法，以及刮痕试验、摩擦学性能研究、应力分析、腐蚀和磨蚀特性研究，也都包括在内。

Coating measurement: In addition to coating properties, there are some features that are relatively easy to test and have standard quality control inspection methods, including visual inspection, measurement of coating thickness and surface roughness measurement. If necessary, the test sample can be sprayed at the same time and under the same conditions, and the coating can be tested in time to determine other properties of the coating quality. In order to accurately determine the coating thickness, porosity and structure, as well as the microstructure of the melted particles and oxide inclusions, the coatings were subjected to lateral cross sectional testing. What’s more, the combination method of strength determination can also

be promoted by using a special glue and test equipment. In addition, some other methods are also useful, including the analysis of various elements, scratch test, tribology properties research, stress analysis, and research of corrosion and abrasion characteristics.