What to do if stainless steel fasteners are locked up
Stainless steel fasteners are a kind of parts that are widely used in our daily life. Compared with carbon steel, stainless steel has good high temperature resistance and corrosion resistance.Asuda stainless steel fasteners are widely used in high-end equipment manufacturing, weapons and equipment, aerospace, rail transit, urban construction, ocean engineering, ocean-going ships, petrochemicals, medical equipment, pressure appliances, new energy, home appliances, communications and other industries.
However, due to the good ductility of stainless steel, stainless steel fasteners often lock up during use. During the tightening process of screws and nuts, the pressure and heat generated between the teeth will destroy and erase the chromium oxide in between. The layer makes the metal tooth pattern directly blocked/sheared, and then the phenomenon of adhesion occurs, making the stainless steel fasteners completely locked, and can no longer be removed or locked, that is, “locked”, commonly known as “seized”.
Why do stainless steel screws lock up?
01 Main reasonThe austenitic 300 series stainless steel material is softer, has good toughness, excellent ductility, is easy to cold work, but has poor thermal conductivity. Therefore, during the tightening process of the fastener, the pressure and heat generated between the teeth will destroy and erase the chromium oxide layer between them; the metal teeth will be blocked/sheared directly, and then stick, resulting in locking.
02 Other reasonsThe product was not selected correctly. Before use, you should confirm whether the mechanical properties of the product can meet the requirements of use, such as the tensile strength of the screw and the safety load of the nut. In addition, if the length of the screw is not selected properly, it will be easy to lock.Rough teeth or sticky foreign matter. If welding slag and other metal shavings are caught between the teeth, it will often lead to lockup. ToUse an electric wrench to tighten. In the process of using the electric wrench, if the force is too large or the locking speed is too fast, the heat generated will melt the chromium oxide layer and cause the lock.The angle of the direction of force is unreasonable. The nut is not screwed perpendicularly to the axis of the screw, and the tilt causes it to lock.How to prevent the screw from locking up?In the process of use, the screw lock phenomenon is a very depressing thing, which leads to equipment damage, delays in working hours, and difficulty in later disassembly. How to prevent the screw from locking, you can do:01Choose the right productReasonably choose the length and specifications of the screw, and the 1-3 pitch of the exposed nut after tightening shall prevail;Before use, confirm whether the mechanical properties of the product can meet the requirements of use;02Reduce friction coefficientThe thread surface is clean (such as no dust, sand, debris);It is recommended to coat the surface with water wax or add lubricant (such as butter, 40# engine oil);
03 The correct method of operationThe screw must be perpendicular to the axis of the thread, and it must not be inclined;During the tightening process, the force must be uniform, and the tightening torque must not exceed the safe torque;
Safety torque table:
| Specification | M4*0.7 | M5*0.8 | M6*1.0 | M8*1.25 | M10*1.5 |
| Safety torque | 2.5 | 5 | 9 | 20 | 40 |
| Specification | M12*1.75 | M14*2.0 | M16*2.0 | M18*2.5 | M20*2.5 |
| Safety torque | 55 | 100 | 150 | 180 | 220 |
| Specification | M22*2.5 | M24*3.0 | M27*3.0 | M30*3.5 | |
| Safety torque | 400 | 510 | 740 | 895 |
Use torque wrenches or socket wrenches as much as possible, and avoid using adjustable wrenches or electric wrenches;Avoid using at high temperature. Do not rotate quickly when in use, to avoid the rapid rise in temperature and cause lockup; (such as using an electric wrench, etc.)04Surface treatment of fastenersAt present, ASUDA has designed three kinds of surface treatments according to the different needs of customers, corresponding to the different needs of customers from the anti-locking effect. Anti-locking wax treatment, anti-locking oil treatment and blue wax treatment can effectively prevent the screw from locking.
