Analysis Of Six Common Problems In Fastener Cleaning
In order to make better use of fasteners, we need to maintain them regularly when using fasteners, such as cleaning them regularly, which can improve the use efficiency of fasteners. However, when we clean fasteners, there are mainly six common problems. As a professional fastener manufacturer, Xinchi Fastener Company will explain them to you one by one.
The pollution produced when rinsing fasteners
After quenching, the fasteners are cleaned with silicate cleaner and then rinsed. Some solid material will appear on the surface. The material is analyzed by the infrared spectrometer and confirmed to be inorganic silicate and iron oxide. This is due to the residue of silicate on the fastener surface caused by incomplete rinsing.
The unreasonable stacking of fasteners
After tempering the fasteners show signs of discoloration, they are soaked and then volatilized to find the oily residue, which is a high content of lipids. It indicates that fasteners are contaminated by cleaning agents and quenching oils during the rinsing period, which melt at heat treatment temperature and leave chemical burning scars. Such substances prove that the fasteners are not clean on the surface. Analyzed with an infrared spectrometer, the substance is a mixture of base oil and ether in quenching oil. The ether may come from the addition of quenching oil. The analysis results of the quenching oil in the mesh belt furnace confirm that the fasteners have slight oxidation in the quenching oil due to unreasonable stacking during heating, but it is almost negligible. This phenomenon is related to the cleaning process, rather than the quenching oil problem.
Surface residue
The white residue on the high-strength screw was analyzed by an infrared spectrometer and confirmed to be phosphide. No acid cleaning agent was performed, and an inspection of the rinsing tank revealed a high carbon solubility. The tank should be emptied regularly and the concentration level of lye in the rinsing tank should be tested frequently.
Alkali burn
High-strength screw quenching residual heat blackening has a uniform, smooth oil black outer surface. But in the outer ring, there is an orange visible area. In addition, there are areas of light blue or light red. Raw rods and rods are coated with phosphating films to facilitate cold heading and tapping and are heat-treated without rinsing. Then it was cooled in quenching oil, cleaned with the alkaline cleaning agent, blow-dried (no rinsing), and tempered at 550℃. In a hot state, it was taken out of the tempering furnace to remove the immersion anti-rust oil. Red spots were found on the screw threads.
Tests showed that the red areas on the screws were caused by alkali burns. If the alkaline cleaning agent contains chlorides or calcium compounds, it will burn the steel fasteners during heat treatment, leaving markings on the fastener surface.
The surface alkalinity of steel fasteners cannot be removed in the quenching oil, so the surface burns at high-temperature austenite and aggravates the injury in the next step of tempering. It is recommended to wash and rinse fasteners thoroughly prior to heat treatment to completely remove alkaline residues that cause burns to fasteners.
Improper rinsing
Polymer water quenching is often used for large-size fasteners. The fasteners were cleaned and rinsed with an alkaline cleaning agent before quenching. The fasteners were rusted on the inside after quenching. Analysis with infrared spectrometers confirmed that in addition to iron oxide, there are sodium, potassium, and sulfur, indicating that the fastener is stuck to the inside of the alkaline cleaning agent, probably potassium hydroxide, sodium carbonate, or similar substances, promoting rust. It is recommended that fastener rinsing be checked for excessive contamination and that the rinsing water is changed frequently. In addition, adding a rust inhibitor to the water is also a good way.
Excessive corrosion
Black stripes are often seen on high-strength fasteners. In the test, it was also observed that the fasteners before heat treatment were rinsed with inorganic and organic cleaning agents. After quenching, black streaks were still found. Even careful cleaning before heat treatment can leave streaks after heat treatment. The infrared spectrometer was used to analyze the residual pollutants on the surface and found that there were high concentrations of sulfur and calcium. With isopropyl alcohol of a small amount of acetic acid, a small piece of test filter paper is forcefully folded over the black spot, leaving the black spot on the filter paper. Calcium, sulfur, iron, manganese and chromium were found to be the main elements in the filter paper.
The presence of calcium and sulfur in the rust indicates that the substance is a dried quenching oil, which is also an evolution of the gas phase during the quenching process. Due to the excessive aging of quenching oil, it is recommended to pour out the old oil, add new oil, and carry out process supervision and quenching oil maintenance throughout the process cycle.
Anji Xinchi Fastening Piece Co., Ltd is a trustworthy fastener company, especially in furniture nuts. And we are the designated fastener supplier to“STAPLE”. As a trusted fastener supplier, Xinchi Fastener Company can offer a wide range of high-quality fasteners, including tee nuts, screws, bolts, rivets, washers, etc. If you want to know more about fasteners or want to wholesale fasteners, please feel free to contact us. And then our experienced and expert service team will reply to you as soon as possible.