1. Basic salt aspect

At present, most QPQ specialized salt manufacturers at home and abroad manufacture bulk base salts after melting, and a small number of them use bulk base salts formed by pressing powdered raw materials. Its manufacturing raw materials are all various non-toxic and heavy metal free chemical raw materials in powder form. The block shaped base salt formed by compression has a certain burning rate during use, requires high environmental protection equipment, has a low salt yield, and poor uniformity of raw materials. The melted bulk base salt is no longer burned during use, resulting in a high salt yield. High usage efficiency.

Usually, a large amount of new salt is added during use, especially when filling new crucibles into the furnace. The base salt formed by pressing usually requires insulation for 12 hours or even longer after melting, and the insulation time after melting will be significantly shortened. If the base salt has not undergone sufficient insulation and aging, the processed product will have severe looseness, and the appearance of the nitrided product will be black (normal nitriding appearance is tile gray). If it continues to oxidize, it is easy to turn red.

In response to such situations in QPQ production, it is recommended to immediately stop production and raise the nitriding furnace temperature to 600 ℃. If there are scrap steel parts, they can be placed in the nitriding furnace to accelerate aging and reduce base salt activity.

2. Adjust the salt aspect

After the completion of QPQ production, there will be varying degrees of consumption of cyanate ions, and it is necessary to timely supplement and adjust the salt to adjust the cyanate ions to the appropriate concentration for the next direct production. At present, there are significant differences in the performance of adjusted salts among different manufacturers on the market, and the most common low-end sequences are urea or urea derived chemical products. In the process of using this type of adjustment salt, there is a large amount of salt mist, high burning loss rate, and low cyanate acquisition rate (according to empirical formulas, adding 2% weight adjustment salt to the furnace base salt can obtain 0.6-1% cyanate), and the working environment is poor. Moreover, it is not possible to produce immediately after adding adjusted salt, especially when adding a large amount of adjusted salt, which must be insulated for a long time before use, otherwise it will cause serious product looseness. High quality and superior performance adjustment salts react quickly and have a high salt yield (according to empirical formulas, adding 2% weight adjustment salt to the furnace base salt can obtain 1-1.4% cyanate ions). This is mainly due to the fact that the purity of the new adjustment salt is much higher than that of urea type adjustment salts. Of course, the yield of cyanate ions is also closely related to the temperature of salt addition and the cleanliness of the base salt.

3. In terms of oxide salts

The main function of oxide salts is to form a uniform and dense oxide film on the surface of the product, significantly improving the corrosion resistance of the workpiece; Secondly, there are small amounts of cyanide and cyanate ions in the nitrogen salts carried out by decomposing the workpiece. When the state of the oxide salt is not good, it can lead to quality problems such as redness and yellowing in the appearance of the product. For new oxide salts, mainly due to their strong alkalinity and strong water absorption, when filling a large amount of new salt in the first furnace to obtain sediment during the production process and adding new salt to replenish the liquid level, there are a large number of water molecules in the salt bath. It is necessary to thoroughly evaporate the water vapor in the salt bath through insulation and aging.

In QPQ production, many quality problems are often caused by workers not controlling the small details in the actual operation process. Corresponding production operation instructions are formulated for the maintenance of products and specialized salts, and real-time attention is paid to the status of specialized salts in order to produce good products.