Throat hoop is a basic mechanical part, which is in great demand. Generally speaking, throat hoop does not need to consider the influence of temperature, harsh environment or other risk conditions. The commonly used materials are carbon steel, low alloy steel and nonferrous metals. However, in special occasions, the data of throat hoop are required to meet the requirements of severe corrosion or high strength, and many stainless steels and ultra-high strength stainless steels emerge as the times require.
This article briefly introduces the excellent stainless steel used for throat hoop production. Most stainless steel materials can be made into steel wire or bar for throat hoop production, including austenitic stainless steel, ferritic stainless steel, martensitic stainless steel and accumulation hardening stainless steel.
Selection criteria:
The selection of stainless steel materials is mainly from the following five aspects.
1. The mechanical function, especially the strength of the hoop is needed.
2. The requirements of working conditions on the anti-corrosion function of data.
3. The requirements of operation temperature on the heat resistance function (high temperature strength, anti-oxidation function) of data.
4. Production technology is facing the needs of data processing function.
5. Other aspects, such as weight, quotation and acquisition, should be considered.
After thinking about all these five aspects, we can conclude the trademark, type, standard and data standard of throat hoop.
Austenitic stainless steel
The commonly used trademarks are 302, 303, 304 and 305, namely the so-called "18-8" austenitic stainless steel. Both corrosion resistance and mechanical function are similar. The starting point of selection is the production technology of throat hoop, which depends on the specification and shape of throat hoop, as well as the quantity of throat hoop.
Type 302 is used to select machined screws and self tapping bolts.
In order to improve the cutting function of 303 type stainless steel, a small amount of sulfur is added to 303 type stainless steel, which is used to select bar material to process nuts.
Type 304 is suitable for processing throat hoop with hot upsetting technology, such as long standard bolts and large diameter bolts, which can exceed the plan of cold upsetting technology.
Model 305 is suitable for processing throat hoop with cold heading technology, such as cold formed nut and hexagon bolt.
309 type and 310 type, their Cr content and Ni content are higher than 18-8 type stainless steel, suitable for throat hoop working at high temperature.
316 and 317 are rich in Mo, so their high temperature strength and corrosion resistance are higher than 18-8 stainless steel.
Type 321 is rich in Ti, type 347 is rich in Nb, and then the intergranular corrosion resistance function of the data is advanced. It is suitable for throat hoops which are not annealed after welding or are in service at 420-1013 ℃.
Ferritic stainless steel
Type 430 ordinary chromium steel has better corrosion resistance and heat resistance than type 410. It is magnetic, but it can not be strengthened by heat treatment. It is suitable for stainless steel throat hoop with higher corrosion resistance and heat resistance and general strength requirement.
Martensitic stainless steel
Type 410 and 416 can be strengthened by heat treatment, with hardness of 35-45hrc and excellent machining function. They are used for heat-resistant and corrosion-resistant throat hoops for general use. Type 416 is a free cutting stainless steel with slightly higher sulfur content.
420 type, sulfur content? 15%, mechanical function, heat treatment strengthening, maximum hardness value 53 ~ 58hrc, used for throat hoop requiring higher strength.
Stack hardening stainless steel
17-4PH, ph15-7mo, they can get higher strength than the general 18-8 type stainless steel, so they are used in high strength, corrosion-resistant stainless steel throat hoop.
A-286, a kind of non-standard stainless steel, has higher corrosion resistance than the commonly used 18-8 stainless steel, and still has excellent mechanical function when the temperature increases. It can be used as high-strength, heat-resistant and corrosion-resistant throat hoop up to 650-700 ℃.
