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热镀锌钢板容易出现的几个问题分析

返回列表 来源: 发布日期: 2019.11.01

热镀锌钢板容易出现的几个问题分析

由于热镀锌钢板的生产工艺和成品包装等因素,部分厂家可能存在以下表面外观缺陷:
(1) 热镀锌钢板原板缺陷

原镀锌板的表面缺陷,如折痕、凹坑、波浪边等,继续影响镀锌板,成为其表面缺陷。因此,在生产之前,生产商需要对原板进行测试。
(2)黑点。
产生黑点的原因有很多,包括:
A. 热镀锌钢板镀锌层纯度不够当金属杂质在锌表面形成原电池时,有利于析氢时,锌层表面容易产生黑点。
B.锌镀层中铜、铁、砷等杂质含量高钝化后,这些杂质是黑色的。
c.原板表面污垢处理不够。在生产过程中,污垢会在表面形成残渣,使部分零件无法镀锌,造成镀锌层缺陷,容易脱落,从而产生黑点。
D.镀锌过程中出现漏镀缺失部分在治疗后容易形成黑点。
e.镀锌溶液中有残留物或少量黑灰(碳或碳化合物)。它附着在锌层表面或驻留在锌层中,并与锌层牢固结合成品镀锌板上可见黑点。
擦伤黑点这是由于运输和堆放过程中的粗暴操作造成的。
锌卷、铝锌板、天丰钢
(3)白锈。
热镀锌钢板当镀锌钢板表面被雨水浸没或浸没时,锌在一定温度下氧化生成白色粉末。白锈表面的防腐能力将大大降低,影响其使用寿命。
(4)锌层不均匀。
镀锌板表面锌层不均匀,厚度不均匀,表面出现细小颗粒。从镀锌锅出来的带钢表面有多余的锌液多余的锌液用气刀(喷射高压气体)吹掉,以控制锌层的厚度。气刀的气压、气刀与带钢的距离、带钢的速度将直接影响锌层的厚度如果气刀供气不稳定或气刀压力不足,锌层会积聚,即锌疤。
(5)含渣镀锌液中有残留物或浮渣(金属或非金属夹杂物)。
有时这些夹杂物在镀锌层中混入,使其表面出现小圆点,甚至使原板不沾锌,容易产生铁斑。

(6)划痕和磨损。
镀锌线圈通过张力矫直机时,矫直机内有异物,造成表面划伤、划伤等。
(7)铬酸垢。
为了提高镀锌钢板的抗腐蚀能力,可以在带钢表面形成一层很薄的钝化层,用铬酸处理,即铬处理。但如果铬酸盐处理不好,且有残留液体,则镀锌板表面会出现浅黄色带或污点,甚至黑点。

Due to factors such as production process and finished product packaging of hot-dip galvanized steel sheet, some manufacturers may have the following surface appearance defects:

(1) defects of the original plate.
The surface defects of the original galvanized sheet, such as creases, pits, wavy edges, etc., continue to affect the galvanized sheet and become its surface defects. Therefore, before production, producers need to test the original board.
(2) black spot.
There are many reasons for black spots, including:
A. the purity of zinc coating is not enough. When metal impurities form primary batteries on the surface of zinc, it is easy to produce black spots on the surface of zinc layer when it is favorable for hydrogen evolution.
B. the content of copper, iron, arsenic and other impurities in the zinc coating is high. After passivation, these impurities are black.
C. the treatment of dirt on the surface of the original plate is insufficient. In the process of production, the dirt will form residue on the surface, which will make some parts unable to be plated with zinc, resulting in the defect of zinc coating and easy falling off, thus causing black spots.
D. missing plating occurs during galvanizing. The missing part is easy to form black spots in post-treatment.
E. there is residue or small black ash (carbon or carbon compound) in the galvanizing solution. It adheres to the surface of zinc layer or resides in the zinc layer, and is firmly bound with the zinc layer. Black spots can be seen on the finished galvanized sheet.
F. abrade black spots. It is caused by rough operation during transportation and stacking.
Zinc coil, aluminum zinc plate, Tianfeng steel
(3) white rust.
Zinc is oxidized to produce white powder at a certain temperature when the surface of galvanized steel sheet is damped or immersed in rainwater. The anti-corrosion ability of the surface with white rust will be greatly reduced, which will affect its service life.
(4) the zinc coating is uneven.
Thezinc layer on the surface of galvanized sheet is uneven, uneven in thickness, and even small particles appear on the surface. There is excess zinc liquid on the surface of the strip steel coming out of the galvanizing pot. The excess zinc liquid is blown off with an air knife (spraying high-pressure gas), so as to control the thickness of the zinc layer. The gas pressure of the gas knife, the distance between the gas knife and the strip steel, and the speed of the strip steel will directly affect the thickness of the zinc layer. If the air supply of the air knife is not stable or the pressure of the air knife is insufficient, the zinc coating will accumulate, that is, the zinc scar.
(5) there are residues or dross (metal or non-metallic inclusions) in the slag containing galvanizing solution.
Sometimes these inclusions are mixed in the zinc coating, making small round spots appear on its surface, even making the original plate not stained with zinc, which is easy to cause iron spots.
(6) scratches and abrasions.
When the galvanized coil passes through the tension leveler, there are foreign matters in the leveler that cause surface scratches, scratches, etc.
(7) chromic acid dirt.
In order to improve the anti-corrosion ability of galvanized steel sheet, a very thin passivation layer can be formed on the surface of the strip, which can be treated by chromic acid, that is, chrome treatment. However, if the chromate treatment is poor and there is residual liquid, the surface of galvanized sheet will appear light yellow band or stain, or even black spot.
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