Users who use stainless steel studs often reflect: why stainless steel fasteners sometimes have locking problems, while similar phenomena do not often occur when using carbon steel fasteners. Is the material of stainless steel fasteners soft? What is the reason why carbon steel fasteners are relatively hard? That's right! Stainless steel and carbon steel are fundamentally different. Stainless steel has good ductility, but its hardness has a certain gap with carbon steel. The hardness of austenitic stainless steel grade 316 and A4-80 can actually only reach 8.8 which is equivalent to the hardness of carbon steel. However, this statement can only be said to be half true.
ThreadGalling often occurs on fasteners made of stainless steel, aluminum alloy and titanium alloy. These types of metal alloys have anti-rust properties. When the surface is damaged, a thin layer will be formed on the metal surface. The oxide layer (in the case of austenitic stainless steel, it is chromium oxide) to prevent further and deeper corrosion. When the stainless steel fastener is locked, the pressure and heat generated between the teeth will destroy and erase the chromium oxide layer between them, causing the metal teeth to directly block/shear, and then the phenomenon of adhesion will occur. When the sticking phenomenon continues (usually no more than one full tooth diameter), the stainless steel fasteners will be completely locked and can no longer be removed or locked. Usually this series of actions of blocking→cutting→adhesive→locking occurs in just a few seconds. Therefore, understanding the characteristics of stainless steel products and following the correct procedures are the first to prevent stainless steel fasteners from locking. step.
The reasons for the locking of stainless steel stud bolts are generally: 1) Rough tooth pattern or foreign matter sticking. If there are solder joints and other metal chips caught between the teeth, it will often lead to locking; 2) Too much force or too fast locking speed, use torque wrenches or socket wrenches as much as possible, and avoid using adjustable wrenches or electric wrenches. Because the electric wrench often causes the locking speed to be too fast, the temperature rises rapidly and locks up; 3) The angle of the direction of force is wrong. The nut must be screwed perpendicular to the axis of the screw, do not tilt; 4) No washers are used. The use of washers can effectively prevent the problem of over-locking.
Scan here
