Quenching medium and processing medium for heat treatment of automotive fasteners

Quenching medium and processing medium for heat treatment of automotive fasteners

Automotive high-strength fasteners have a series of technical characteristics: high precision grade; severe service conditions, it will be with the host together with the year-round exposure to cold and extreme temperature differences to withstand high and low-temperature erosion; static load, dynamic load, overloading, heavy loads and corrosion of the environmental media, in addition to axial pre-tensioned tensile load, but also the work of the additional tensile alternating load, transverse shear alternating load or thereby Composite of the bending load, and sometimes by the impact load; additional transverse alternating load will cause bolt loosening, the axial alternating load will cause bolt fatigue fracture, the axial tensile load will cause bolt delayed fracture, as well as high-temperature conditions caused by bolt creep.

Alloy Steel Shoulder Screws： Comparable to Grade 8 steel, these alloy steel shoulder screws are the strongest we offer. They have a standard shoulder with an undersized tolerance for most machinery and equipment. Also known as stripper bolts, they're commonly used in punch and die assemblies and as an axle or pivot point.

Metric Alloy Steel Thread-Locking Shoulder Screws： A locking element on the threads adds friction to resist loosening. Comparable to Class 12.9 steel, these alloy steel shoulder screws are the strongest we offer. They have a standard shoulder with an undersized tolerance for most machinery and equipment. Also known as stripper bolts, they're commonly used in punch and die assemblies and as an axle or pivot point.

Torx Alloy Steel Socket Head Screws： A Torx-Plus drive has more points of contact than a hex drive, allowing you to tighten these screws with less slippage or damage to the recess. With a tensile strength of 180,000 psi, these alloy steel screws are more robust than Grade 8 steel screws. Their black-oxide finish provides mild corrosion resistance in dry environments. They can be used with both Torx-Plus and standard Torx tools (see Torx bits and Torx keys and drivers). Screws meet ASTM A574 specifications and testing requirements for material quality. Length is measured from under the head.

Coarse threads are the industry standard; choose these screws if you'd don't know the threads per inch. Fine threads are closely spaced to prevent loosening from vibration. They are not compatible with coarse threads. For high-quality High-Alloy Steel Shoulder Screws fasteners and professional technical support, don't hesitate to co don't us at adelajonly@gmail.com or visit our website at [Juxin Fasteners]: https://www.juxinfasteners.com.

Many failed bolts show that the service for the transition along the head of the bolt and the rod fracture, along the bolt rod threads and intersection, is pulled off and along the threaded part of the slip buckle.

Metallographic analysis: The bolt surface and the heart contain more undissolved ferrite. In the quenching, austenitization is insufficient, the matrix strength is inadequate, and stress concentration is one of the essential reasons for failure.

For this reason, ensuring that the bolt cross-section quenching and organization uniformity are very important

The function of quenching oil is to take away the heat of the red-hot metal bolts quickly so that it is reduced to the martensitic transformation temperature to obtain a high degree of hardness of the martensitic organization and depth of the hardened layer while also taking into account the reduction of deformation of the bolts and to prevent cracking. Therefore, the essential characteristic of quenching oil is "cooling characteristics," which is characterized by the high-temperature stage of the cold speed being faster, while the low-temperature stage of the cold speed is slower; this characteristic is very suitable for alloy structural steel ≥ 10.9 grade above the quenching requirements of high-strength bolts.

Fast quenching oil is in use due to thermal decomposition, oxidation, and polymerization reactions, which leads to changes in cooling characteristics. The oil contains a small amount of water, which will seriously affect the cooling performance of the oil, resulting in a decrease in the brightness of the quenched fasteners; hardness is not uniform, resulting in a soft spot or even cracking tendency. Studies have shown that the deformation problem produced by oil quenching is partly caused by water in the oil. In addition, water in the oil also accelerates the emulsification of oil deterioration and promotes the failure of additives in the oil. When the water content in the oil ≥ 0.1%, when the oil is heated, it is possible to make the water gathered at the bottom of the tank reach the boiling point; the volume of the sudden expansion easy to causes the oil to overflow, quenching oil tank and cause a fire.

For the continuous mesh belt furnace using rapid quenching oil, according to the quenching characteristics data accumulated in the 3-month interval test, it is possible to establish the stability of the oil and quenching characteristics of the map, to determine the appropriate service life of the quenching oil, to predict the problems associated with changes in the performance of the quenching oil, to reduce the loss of rework or scrap due to the changes in the performance of the quenching oil, to make it a routine control method of production. The quenching depth directly affects the bolt's quality after heat treatment. When the hardenability of the material is poor, the cooling rate of the cooling medium is slow, and the size of the bolt is large, the quenching of the bolt heart is not possible with the martensite organization, which reduces the level of strength in the heart region, especially the yield strength. This is unfavorable for bolts subjected to uniformly distributed tensile stresses along the cross-section. Insufficient hardenability reduces the strength, and metallographic examination reveals the presence of pre-eutectic ferrite and reticulated ferrite organization in the heart, indicating that the hardenability of the bolt needs to be strengthened. It is well known that the two ways to increase the hardenability, improve the quenching temperature, and increase the hardening capacity of the quenching medium can effectively increase the hardening depth of the bolt.

Based on the original medium-speed quenching oil, Houghto-Quench G's unique development of rapid quenching oil, Houghto-Quench K2000 to further improve its hardening ability, especially suitable for use in the quenching and cooling of fasteners, can obtain a satisfactory depth of hardening.

Rapid quenching oil vapor film stage is short, that is, the high-temperature stage of the oil-cooled quickly; this feature is conducive to 10B33, 45 steel ≤ M20 bolts, and M42 nuts to obtain a deeper hardened layer, and for SWRCH35K, 10B28 steel is thinned to ≤ M12 bolts, M30 nuts to ensure that the heart of the hardness and the surface hardness of the slight difference. From the cooling rate distribution analysis, in addition to the medium and high-temperature stages requiring cooling fast, the low-temperature cooling rate of oil to obtain the hardened layer depth role is greater; the higher the low-temperature cooling rate, the hardened layer tends to be more profound. This is for high-strength fasteners throughout the cross-section of the uniform load-bearing requirements in the quenched state, tempering before obtaining about 90% of the martensite organization, which is favorable. The indicators are flash point, viscosity, acid value, oxidation resistance, residual carbon, ash, sludge, quenching cooling rate, brightness, and nearly 20 other indicators.

For larger specification bolts or PAG quenching agents to meet the quenching requirements of most products, PAG quenching agent in the martensitic transformation zone is in the boiling stage, the cooling rate is significant, and there is a greater risk that it can be adjusted through the concentration of the critical indicators of the cooling rate of 300 ℃ or so, the lower the rate of cooling at this temperature point, to prevent quenching and cracking of the ability of the more robust, applicable to more steel types. The stability of the convection cold speed in the use process is the most critical factor in ensuring quenching quality.

In the early failure of the bolt specimen, also visible in the fracture bolt near the fracture of the threads are present on the crack defects, mainly bolts of the rolling process is not appropriate, in the rolling of the thread in the cold forming process of metal plastic rheological convergence and folding caused by; in the bottom of the threaded teeth can also be seen in the presence of varying shades of micro-cracks, processing of chip tumors in the formation of the stress concentration zone. Fastener surface defects bolts, screws, and studs special requirements" standard, for the stress of the bolt threads above the depth of the mid-diameter, is not greater than one-quarter of the height of the threaded teeth folding is permitted; the bottom of the threaded teeth of the folding and accumulation of chip tumors is not allowed defects, and folding is one of the main reasons for the bolt fracture. Using extreme pressure lubricants for bolt threading by Good Fulton can effectively prevent chip tumors and reduce stress concentration, thus helping to improve the fatigue life of bolts.