Introduction About Stainless Steels

There are more than 250 different stainless steels. These various
grades of stainless are divided into five major families or classes as shown on table below.
The general classes have been developed to consolidate the
chemistries and mechanical properties required to meet specific customer
application needs.(1)

Stainless steel is not as easy as ordinary steel rust. Chromium is the basic element of corrosion resistance of stainless steel, the addition of chromium and nickel in the steel to produce rust-proof oxide film on its surface, thus protecting the steel itself by the air (especially oxygen), water, Alkali corrosion, in order to maintain the inherent corrosion resistance of stainless steel , steel must contain more than 12% of chromium , in addition to chromium, the commonly used alloying elements are nickel, molybdenum, titanium, niobium, copper, nitrogen, to meet the various Use of stainless steel for the organization and performance requirements.

Stainless steel by organization

Stainless type Main ingredient characteristic commonly used steel

Ferritic Contains 12 % to 30% Resistance to chloride stress corrosion is SS 409

Stainless Steel chromium,its better than other types of stainless steel. Of Aluminized 409

corrosion resistance this type of ferritic stainless steel because of SS 409 Ni

toughness and high chromium content, corrosion resistance SS 41003

weldability with the and oxidation resistance are better, but the SS 430,436,439

increase in chromium mechanical properties and process SS 435 Mod

contenr increased performance is poor, and more for the SS 18 SR

resistance of acid structure and for the use of SS 18 cr-cb

anti-oxidation steel. SS 444

Austenitic Containing more than Comprehensive performance is good, can Sus 301

Stainless Steel 18% chromium, also withstand a variety of media corrosion. sus 304

contains about 8% of 0Cr19Ni9 steel wC <0 .08="" as="" marked="" steel="" td=""> sus 304L

nickel and a small "0". This kind of steel contains a lot of Ni sus 316

amount of and Cr, so that steel at room temperature was sus 316L

molybdenum, titanium austenitic state. This type of steel has good sus 321

nitrogen and other plasticity, toughness, weldability and

elements corrosion resistance.

Duplex Austenitic and ferrite Both the austenitic and ferritic stainless steel NITRONIC 19D

Stainless Steel organizations account characteristics, compared with the ferrite, 2205

for about half of the plasticity, higher toughness, no room

stainless steel. In the temperature brittleness, resistance to

case of low C, Cr intergranular corrosion and welding

content of 18% to 28%, performance are significantly improved,

Ni content of 3% to while also maintaining ferrite Stainless steel

10%. Some steel also 475 ℃ brittleness and high thermal

contains Mo, Cu, Si, conductivity, with superplasticity and so on.

Nb, Ti, N and other

alloying elements

Martensitic Chromium content of High strength, but poor plasticity and SS 410

stainless steel not less than 12% weldability. Due to high carbon content, it SS 410H

(usually 12% to 18%), has a high strength, hardness and wear SS 420

high carbon content resistance, but the corrosion resistance is SS 420 HC

slightly worse for high mechanical

properties, corrosion resistance requirements

of some general parts, such as springs,

turbine blades, hydraulic valve Wait. This

type of steel is used after quenching and

tempering

Precipitation- Consist of 14-17.5% of Hight strength and hardness and excellent 2205

Hardening chromium,4-7.5% of fatigue properties, and their application use NITRONIC 19 D

steels nickel and other alloy on Aerospace,chemical and

elements petrochemical,food processing

Stainless type	Main ingredient	characteristic	commonly used steel
Ferritic	Contains 12 % to 30%	Resistance to chloride stress corrosion is	SS 409
Stainless Steel	chromium,its	better than other types of stainless steel. Of	Aluminized 409
	corrosion resistance	this type of ferritic stainless steel because of	SS 409 Ni
	toughness and	high chromium content, corrosion resistance	SS 41003
	weldability with the	and oxidation resistance are better, but the	SS 430,436,439
	increase in chromium	mechanical properties and process	SS 435 Mod
	contenr increased	performance is poor, and more for the	SS 18 SR
		resistance of acid structure and for the use of	SS 18 cr-cb
		anti-oxidation steel.	SS 444

Austenitic	Containing more than	Comprehensive performance is good, can	Sus 301
Stainless Steel	18% chromium, also	withstand a variety of media corrosion.	sus 304
	contains about 8% of	0Cr19Ni9 steel wC <0 .08="" as="" marked="" steel="" td="">	sus 304L
	nickel and a small	"0". This kind of steel contains a lot of Ni	sus 316
	amount of	and Cr, so that steel at room temperature was	sus 316L
	molybdenum, titanium	austenitic state. This type of steel has good	sus 321
	nitrogen and other	plasticity, toughness, weldability and
	elements	corrosion resistance.

Duplex	Austenitic and ferrite	Both the austenitic and ferritic stainless steel	NITRONIC 19D
Stainless Steel	organizations account	characteristics, compared with the ferrite,	2205
	for about half of the	plasticity, higher toughness, no room
	stainless steel. In the	temperature brittleness, resistance to
	case of low C, Cr	intergranular corrosion and welding
	content of 18% to 28%,	performance are significantly improved,
	Ni content of 3% to	while also maintaining ferrite Stainless steel
	10%. Some steel also	475 ℃ brittleness and high thermal
	contains Mo, Cu, Si,	conductivity, with superplasticity and so on.
	Nb, Ti, N and other
	alloying elements

Martensitic	Chromium content of	High strength, but poor plasticity and	SS 410
stainless steel	not less than 12%	weldability. Due to high carbon content, it	SS 410H
	(usually 12% to 18%),	has a high strength, hardness and wear	SS 420
	high carbon content	resistance, but the corrosion resistance is	SS 420 HC
		slightly worse for high mechanical
		properties, corrosion resistance requirements
		of some general parts, such as springs,
		turbine blades, hydraulic valve Wait. This
		type of steel is used after quenching and
		tempering

Precipitation-	Consist of 14-17.5% of	Hight strength and hardness and excellent	2205
Hardening	chromium,4-7.5% of	fatigue properties, and their application use	NITRONIC 19 D
steels	nickel and other alloy	on Aerospace,chemical and
	elements	petrochemical,food processing

Stainless steel general characteristic

Surface appearance and the use of the possibility of diversification
Good corrosion resistance, longer than ordinary steel durable
Good corrosion resistance
High strength, so the possibility of use of thin plate
High temperature oxidation and high strength, so it can fire
At room temperature processing, that is easy to plastic processing
Because it is not necessary to deal with it, so it is simple and easy to maintain
Clean, high finish
Welding performance is good

Stainless steel Cutting Characteristic

Work hardening serious: in stainless steel, austenitic and austenite + ferritic stainless steel processing hardening phenomenon is most prominent. Stainless steel plasticity, plastic deformation when the character crooked, strong coefficient and austenite is not stable enough, under the action of cutting stress, part of the austenite will be transformed into martensite; coupled with the compound impurities in the cutting heat Under the effect of easy decomposition of the dispersion was distributed, so that the hardening layer when cutting. Prior to the feed or a process before the work hardening caused by the serious impact of the subsequent process of the smooth progress.
Large cutting force: stainless steel in the cutting process of plastic deformation, especially austenitic stainless steel (the elongation of more than 45 times the steel more than 1.5 times), so that increased cutting force. At the same time, stainless steel processing hardening serious, high thermal strength, and further increase the cutting resistance, chip crimping break is also more difficult.
High cutting temperature : plastic deformation during cutting and milling and milling are very large, resulting in cutting heat; plus stainless steel thermal conductivity of about 45 steel ½ ~ ¼, a large number of cutting heat are concentrated in the cutting area and Knife - chip contact on the interface, poor heat dissipation conditions.
Chip is not easy to break, easy to bond: stainless steel plasticity, toughness are great, the car processing chip continuously, not only affect the smooth operation, the chip will crush the processed surface. In the high temperature, high pressure, stainless steel and other metals affinity and strong, easy to produce adhesion phenomenon, and the formation of BUE, both exacerbate the tool wear , there will be tearing the phenomenon of processing has deteriorated. This feature of the lower carbon content of martensitic stainless steel is more pronounced.
Easy wear of the tool : cutting the role of stainless steel in the process of affinity, so that the knife-chip between the bonding, diffusion, so that the tool has a bond wear and tear, diffusion wear and tear, resulting in tool nose face crescent depression, cutting edge will form a small (Such as TiC) fine particles of high hardness, cutting directly with the tool contact, friction, scratches the tool, as well as the work of hardening phenomenon, will make the tool wear intensified.
Linear expansion coefficient: stainless steel linear expansion coefficient of carbon steel is about 1.5 times, under the action of cutting temperature, the workpiece is prone to thermal deformation, dimensional accuracy is difficult to control.