Classification of stainless steel screwsClassification of stainless steel screws
Stainless steel screws are classified into austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, and precipitation hardening stainless steel. The selection of stainless steel screws is also principled. From
what aspect, let you choose the stainless steel screws you need. After comprehensive consideration of these five aspects, the grades, varieties, specifications and material standards of stainless steel screws are finally determine
Austenitic stainless steel: The most basic alloying elements of austenitic stainless steel are chromium and nickel. The representative grade is chromium-nickel austenitic stainless steel with a chromium content of about 18% and a nickel
content of about 8%, often called 18 -8 stainless steel. The element ratio of chromium and nickel basically ensures that the steel structure is stable austenite
Ferritic stainless steel: 430 type ordinary chromium steel, its corrosion resistance and heat resistance are better than 410 type, and it is magnetic, but it cannot be strengthened by heat treatment. It is suitable for relatively high
corrosion resistance and heat resistance. Normal stainless steel screws are requMartensitic stainless steel: Type 410 and Type 416 can be strengthened by heat treatment, with a hardness of 35～45hrc, good machining performance, heat-
resistant and corrosion-resistant stainless steel screws for general purposes.
Type 416 has a slightly higher sulfur content and is a free-cutting stainless steel. Type 420, sulfur content ?r0.15%, improved mechanical properties, can be strengthened by heat treatment, with a maximum hardness of 53～58hrc, used for
stainless steel screws requiring higher strengthired
Precipitation hardening stainless steel: 17-4ph, ph15-7mo, they can get higher strength than the usual 18-8 type stainless steel, so they are used for high-strength, corrosion-resistant stainless steel screws.
a-286, a non-standard stainless steel, has higher corrosion resistance than the commonly used 18-8 type stainless steel, and still has good mechanical properties when the temperature increases. Used as high-strength, heat-resistant and
corrosion-resistant stainless steel screws, which can be used at 650-7Austenitic stainless steel: The commonly used models are 302, 303, 304, and 305, which are the so-called "18-8" austenitic stainless steels. Both the corrosion
resistance and the mechanical properties are similar. The starting point for selection is the production process of stainless steel screws, and the method depends on the size and shape of the stainless steel screws, as well as the
quantity of production.
Type 302 is used for machined screws and self-tapping bolts.00°C.
In order to improve the cutting performance of Type 303, a small amount of sulfur is added to Type 303 stainless steel, which is used to machine nuts from bar stock.
Type 304 is suitable for processing stainless steel screws with hot heading, such as longer bolts and large diameter bolts, which may be beyond the scope of cold heading.
Type 305 is suitable for processing stainless steel screws with cold heading technology, such as cold-formed nuts and hexagonal bolts.
Types 309 and 310 have higher cr content and ni content than 18-8 type stainless steel, which are suitable for stainless steel screws working at high temperatures.
Types 316 and 317, they both contain the alloying element mo, so their high temperature strength and corrosion resistance are higher than those of 18-8 type stainless steel.
321 type and 347 type, 321 type contains relatively stable alloying element ti, 347 type contains nb, thus improving the material's resistance to intergranular corrosion. Suitable for stainless steel standard parts that are not annealed
after welding or are in service at 420～1013℃.