The introduction of stainless steel

5.the characteristics of stainless steel

1. General characteristics

Beautiful surface and the possibility of diversification of use

Good corrosion resistance, long-lasting than ordinary steel

Good corrosion resistance

High strength, so the possibility of using thin plates

High temperature oxidation resistance and high strength, so it can resist fire

Normal temperature processing, i.e., easy plastic processing

Easy and simple maintenance because surface treatment is not necessary

High cleanliness and finish

Good welding performance

2、Quality characteristics

2-1 Quality characteristics of stainless steel

Item Basic organization

Representative steel grade STS304 STS430 STS410

Heat treatment solid melt heat treatment annealing annealing and rapid cooling

Hardness Process hardening Slight hardening Small amount of hardening

Main applications Interior and exterior decoration of buildings, kitchen utensils, chemical scales, aerospace equipment, construction materials, automotive parts, appliance, kitchen utensils, lunch boxes, etc. Brazier and knife parts, hospital utensils, surgical utensils

Corrosion resistance High High Medium

Strength High Medium High

Workability High Medium High

Magnetism Non-magnetic Upper magnetic Upper magnetic

Weldability High Medium Low

2-2 Stainless steel quality characteristics required Application Object product Processing process Required quality characteristics

Surface quality BQ material shape thickness tolerance weldability corrosion resistance

Shallow processing knives, forks, etc. Drop → cross extension → cutting head → forming → polishing → cleaning → packaging high requirements shall not have defects such as pitting good general material general -5% not required good

Deep processing class Two types of tableware, insulation cups, etc. Material → oiling → forming → (sometimes several times) cutting edge → rolled edge → cleaning → re-bottom → polishing → welding handle → packaging High requirements shall not have scratches and creases and other defects Good DDQ high requirements -3 ~ -5% Good Good

PIPE decorative tubes and other narrow strips → extrusion into pressure forming → butt welding → polishing welding seam → pipe cutting → grinding mouth → polishing → packaging high requirements shall not have creases and other defects general general material good -8% good general

The outer wall of the kitchen cold cabinet etc. is dropped→folded→electric welding→polishing high requirements shall not have creases and other defects general general material general-8% good general

Vessel water heater drinking fountain liner narrow strip → roll → welding → pipe cutting → welding bottom → polishing weld → packaging general general general material general -10% good general

※The quality requirements of processing and raw materials are different for each product due to the different uses.

2-3 Quality requirements characteristics microfine items

(1) Material.

① DDQ (deep drawing quality) material: refers to the material used for deep drawing (punching) purposes, which is what we call soft material, the main feature of this material is a high elongation (≧ 53%), low hardness (≦ 170%), internal grain grade between 7.0 ~ 8.0, deep punching performance is excellent. At present, many production of thermos bottles, pots and pans, the processing ratio of its products (BLANKING SIZE / product diameter) are generally higher, their processing ratio of 3.0, 1.96, 2.13, 1.98. SUS304 DDQ with material is mainly used for these requirements of higher processing ratio of products, of course, processing ratio of more than 2.0 products are generally required after several times of Stretching to complete. If the extension of raw materials can not reach, in the processing of deep-drawn products, the product is very easy to produce cracks, pull through the phenomenon, affecting the finished product qualification rate, of course, also increases the cost of manufacturers.

②general material is mainly used in addition to DDQ use of materials, this material is characterized by relatively low elongation (≧ 45%), and relatively high hardness (≦ 180), internal grain size grade between 8.0 ~ 9.0, and DDQ with the material, its deep punching performance is relatively slightly worse, it is mainly used for products that can be obtained without stretching, such as a class of tableware spoons, spoons, forks, electrical appliances, steel pipes Use, etc. But it has an advantage compared with DDQ material, that is, BQ sex is relatively good, which is mainly due to its slightly higher hardness.

(2) Surface quality.

Stainless steel sheet is a very high priced material, and customers have very high requirements for its surface quality. But stainless steel sheet in the production process will inevitably appear a variety of defects, such as scratches, pockmarks, creases, pollution, etc., and thus its surface quality, such as scratches, creases, etc. These defects are not allowed to appear whether it is a senior material or low-grade, and pockmarks such defects in the spoon, spoon, fork, production is never allowed, because polishing is difficult to throw it off. We determine the surface quality grade according to the degree and frequency of various defects on the surface, so as to determine the product grade.

(3) Thickness tolerance.

Generally speaking, the different stainless steel products, the requirements of the thickness tolerance of raw materials vary, such as the second class tableware and insulation cups, etc., the thickness tolerance is generally required higher, -3 ~ 5%, while a class of tableware thickness tolerance is generally required -5%, steel pipe class requirements -10%, the hotel with the thickness tolerance of cold cabinet material requirements for -8%, the dealer requirements for thickness tolerance is generally between -4% to 6%. At the same time, the difference between domestic and foreign sales of products will also lead to different requirements of customers on the thickness tolerance of raw materials. General export products customer thickness tolerance requirements are higher, while the domestic sales enterprises on the thickness tolerance requirements are relatively low (mostly for cost considerations), some customers even require -15%.

(4) weldability.

Product use of different welding performance requirements are also different. A class of tableware on the welding performance is generally not required, even including some pot enterprises. But the vast majority of products need raw materials welding performance is good, like the second class tableware, insulation cups, steel pipes, water heaters, water dispensers, etc..

(5) Corrosion resistance.

The vast majority of stainless steel products require good corrosion resistance, such as one or two types of tableware, kitchenware, water heaters, drinking fountains, etc. Some foreign businessmen on the product also do corrosion resistance test: NACL aqueous solution heated to boiling, pour off the solution after a period of time, wash and dry, weigh the loss, to determine the degree of corrosion (Note: the product polishing, because of the composition of the sand cloth or sandpaper containing Fe, will lead to test (when the surface rust spots)

Polishing performance (BQ sex).

At present, stainless steel products are generally polished in the production of this process, only a few products such as water heaters, water dispenser lining, etc. do not need to polish. Therefore, this requires a good polishing performance of raw materials. The main factors affecting the polishing performance are the following.

① raw material surface defects. Such as scratches, pockmarks, over acid washing, etc..

② raw material material problems. Hardness is too low, polishing is not easy to polish bright (BQ sex is not good), and hardness is too low, the surface is prone to orange peel phenomenon when deep drawing, thus affecting the BQ sex. High hardness of BQ sex is relatively good.

③ After deep drawing of the product, the surface of the area of great deformation will also be small black spots and RIDGING, which affects the BQ sex.