Blackening is a common means of metal heat treatment. The principle is to produce an oxide film on the metal surface to insulate the air and achieve the purpose of rust prevention. When the appearance requirement of ND steel pipe is not high, blackening treatment can be used. The surface blackening treatment of steel parts is also called blueing. Blueing treatment is a kind of chemical surface treatment. Its main function is to form a dense oxide film on the surface of the workpiece to prevent corrosion and rust of the workpiece and to improve the wear resistance of the workpiece. It is only a surface treatment, and it will not have any effect on the internal structure. It is not heat treatment, but is fundamentally different from quenching.
nd钢管发黑处理现在常用的方法有传统的碱性加温发黑和出现较晚的常温发黑两种。但常温发黑工艺对于低碳钢的效果不太好。 碱性发黑细分出来，又有一次发黑和两次发黑的区别。nd钢管发黑液的主要成分是氢氧化钠和亚硝酸钠。发黑时所需温度的宽容度较大，大概在135到155℃之间都可以得到不错的表面，只是所需时间有些长短而已。 工艺： 金属“发蓝”药液 nd钢管采用碱性氧化法或酸性氧化法；使金属表面形成一层氧化膜，以防止金属表面被腐蚀，此处理过程称为“发蓝”。 黑色金属表面经“发蓝”处理后所形成的氧化膜，其外层主要是四氧化三铁，内层为氧化亚铁。 一、碱性氧化法“发蓝”药液 1．配方： 硝酸钠50～100克氢氧化钠600～700克亚硝酸钠100～200克水1000克 2．制法：按配方计量后，在搅拌条件下，依次把各料加入其中，溶解，混合均匀即可。 3．说明： （1）金属表面务必洗净和干燥以后，才能进行“发篮”处理。 （2）金属器件进行“发蓝”处理条件与金属中的含碳量有关，“发蓝”药液温度及金属器件在其中的处理时间可参考下表。 金属中含碳量%工作温度（℃）处理时间（分）开始终止>0.7135-13714310-300.5-0.7135-14015030-50<0.4142-145153-15540-60合金钢142-145153-15560-90 （3）每隔一星期左右按期分析溶液中硝酸钠、亚硝酸钠和氢氧化钠的含量，以便及时补充有关成分。一般使用半年后就应更换全部溶液。 （4）金属“发蓝”处理后，最好用热肥皂水漂洗数分钟，再用冷水冲洗。然后,又用热水冲洗，吹于。
There are two commonly used methods for blackening treatment of ND steel pipes: traditional alkaline heating blackening and late room temperature blackening. But the effect of blackening at room temperature on low carbon steel is not very good. The alkaline blackening is subdivided into two parts, one blackening and two blackening. The main components of blackening liquor for ND steel pipe are sodium hydroxide and sodium nitrite. The temperature tolerance required for blackening is relatively large, and a good surface can be obtained between 135 and 155 degrees Celsius, but the time required is only a little longer. Process: Metal "bluing" liquid ND steel pipe adopts alkaline oxidation method or acid oxidation method; the metal surface forms an oxide film to prevent metal surface from being corroded. This process is called "bluing". The oxide film formed on the black metal surface after "bluing" treatment is mainly composed of ferric oxide in the outer layer and ferrous oxide in the inner layer. Formula: sodium nitrate 50-100 grams of sodium hydroxide 600-700 grams of sodium nitrite 100-200 grams of water 1000 grams 2. Method: According to formula measurement, under stirring conditions, each material is added in turn, dissolved, and mixed evenly. 3. Description: (1) The metal surface must be washed and dried before the "basket" treatment can be carried out. (2) The condition of "bluing" treatment for metal devices is related to the carbon content in the metal. The temperature of "bluing" liquid and the processing time of metal devices can be referred to in the table below. The treatment time (minute) of carbon content% working temperature (minute) begins to terminate > 0.7135-13714310-300.5-0.7135-14015030-50 < 0.4142-145153-15540-60 alloy steel 142-145153-15560-90 (3) periodically analyses the contents of sodium nitrate, sodium nitrite and sodium hydroxide in the solution every other week or so in order to supplement the relevant components in time. Generally, all solutions should be replaced after half a year of use. (4) After metal "bluing" treatment, it is better to rinse it with hot soapy water for several minutes and then rinse it with cold water. Then rinse it with hot water and blow it.
2. Acidic oxidation method "bluing" solution
1. Formula: 3-10 g phosphate, 80-100 g calcium nitrate, 10-15 g manganese peroxide, 1000 g water
2. Method of preparation: After measuring according to the formula, phosphoric acid, manganese peroxide and calcium nitrate are added in turn under the condition of continuous stirring, dissolve and mix evenly.
3．说明： （1）金属器件先经洗净和干燥后才能进行“发蓝”处理。 （2）此法所得保护膜呈黑色，其主要成分是由磷酸钙和铁的氧化物所组成，其耐腐能力和机械强度均超过碱性氧化法所得的保护膜。
3. Description: (1) Metal devices can be "blued" only after being washed and dried. (2) The protective film obtained by this method is black, and its main component is composed of oxides of calcium phosphate and iron. Its corrosion resistance and mechanical strength are higher than those obtained by alkaline oxidation method.
4.“发蓝”工作温度为100℃，处理时间为40～45分钟。在处理碳素钢时，药液中磷酸含量控制在3～5克／升；处理合金钢或铸钢时，磷酸含量控制在5～10克／升。应注意定期分析药液磷酸的含量。 5.“发蓝”处理后金属器件的清洗方法同上。 1、清洗； 2、脱脂：工件必须完全浸入脱脂液中；脱脂液浓度ph值12-14，处理时间10-30min，每过3-5分钟上下抖动几次，药液浓度低于ph12时补充脱脂粉； 3、水洗； 4、酸洗：酸洗液浓度ph值2-4，处理时间5-10min； 5、水洗； 6、发黑：池液浓度ph值2.5-3.5，处理时间10-12min； 7、水洗； 8、吹干 9、上油。
4. The working temperature of "bluing" is 100 C and the treatment time is 40-45 minutes. When carbon steel is treated, the content of phosphoric acid in liquid medicine is controlled at 3-5 g/l, and when alloy steel or cast steel is treated, the content of phosphoric acid is controlled at 5-10 g/l. Pay attention to periodic analysis of the content of phosphoric acid in medicinal liquid. 5. The cleaning method of metal devices after "bluing" treatment is the same as the above. 1. Cleaning; 2. Degreasing: the workpiece must be completely immersed in degreasing solution; the concentration of degreasing solution is 12-14, the treatment time is 10-30 minutes, shaking up and down several times every 3-5 minutes, the concentration of liquid medicine is lower than pH 12, adding degreasing powder; 3, washing; 4, pickling: the concentration of acid washing solution is 2-4, the treatment time is 5-10 minutes; 5, washing; 6, blackening: the concentration of pool liquid is 2.5-3.5, the treatment time is 10-12 minutes. 7. Washing; 8. Blowing and drying; 9. Oiling.
效果：（1）发黑安全不用电，用碱性高温发黑需100%用电。（2）提高工效：共需1-2小时。（3）发黑成本低，设备简单，操作方便；对发黑时间作了严格的控制。（4）工艺适应性强：解决了球墨铸铁不能发黑的难题。一种轴承套圈倒角及挡边的发蓝防锈处理工艺。轴承套圈在热处理后经过除油脱脂，然后在氢氧化钠、亚硝酸钠、硝酸钠和水的混合溶液中进行变色处理，其配比为2-3∶1，其余加水；加水量以温度在 135℃-145℃为合适；时间15-25分钟；取出套圈用清水冲洗后进行钝化处理，钝化处理用重铬酸钾溶液作为填充液，其浓度为12%-18%；在室温下 1-2分钟；经钝化处理并干燥后，放入105℃-120℃的机油或防锈油中 1-3分钟，至气泡完全消失后取出，停放10-15分钟后检验。本发明生成的氧化物薄膜性能稳定，在常温下可长期保护套圈倒角、挡边处不生锈，轴承的外观质量得到明显改善。 A3钢用碱性发黑好一些。实际操作中，需要注意的是工件发黑前除锈和除油的质量，以及发黑后的钝化浸油。发黑质量的好坏往往因这些工序而变化。
Effect: (1) Blackening is safe and does not use electricity. It needs 100% electricity to blacken with alkaline high temperature. (2) Improve work efficiency: 1-2 hours in total. (3) The blackening cost is low, the equipment is simple and the operation is convenient, and the blackening time is strictly controlled. (4) Strong process adaptability: Solve the problem that nodular cast iron can not blacken. The invention relates to a blue rust-proof treatment process for chamfering of bearing rings and shielding edges. After heat treatment, bearing rings are degreased and degreased, and then discolored in the mixed solution of sodium hydroxide, sodium nitrite, sodium nitrate and water. The ratio is 2-3:1, and the rest is added water. The appropriate amount of water is at 135-145 C. The time is 15-25 minutes. The rings are washed with clean water and passivated with potassium dichromate solution as filling liquid. Its concentration is 12%-18%. It is 1-2 minutes at room temperature. After passivation and drying, it is put into 105-120 C oil or rust-proof oil for 1-3 minutes. After the bubble disappears completely, it is removed and tested after 10-15 minutes. The oxide film produced by the invention has stable performance, can protect the chamfer and the edge of the ring for a long time under normal temperature, and the appearance quality of the bearing is obviously improved. Alkaline blackening is better for A3 steel. In practice, attention should be paid to the quality of rust and oil removal before blackening and passivation soaking after blackening. The quality of blackening often varies with these processes.
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