1. The application of stainless steel in fastening piece
Stainless steel fastening pieces are widely used in auto industry, infrastructure, family appliances, communication and furniture industry and various other industries. Cr-Ni austenite steel is mainly used in fastening pieces industry, which occupies 85%, and Cr series (ferrite, martensite) occupy 15%. The main brand is 0Cr18Ni9, in recent years, the austenite steel that contains Cu and is easy cold upsetting forming has become the main steel type. The fact is, by considering the actual requirements, most stainless steel brand can be used to make fastening pieces, but the large sums of current fastening pieces mainly use austenite stainless steel.

In China, in the stainless steel fastening piece standard GB3098.6 -86, due to steel quality, the stainless steel is divided into three classes including A class (austenite), C class (martensite) and F class (ferrite), and among each class, rankings are made due to differences of the steel type.

The classification of stainless steel fastening pieces

Class	Serial number	Steel type
A(austenite)	A1 A2 A4	1Cr18Ni9 series steel 0Cr18Ni9 series steel 0Cr17Ni12Mo2 series steel
C(martensite) F(ferrite)	C1 C2 C4 F1	Cr12 type mertensite stee Cr-Ni mertensite series steel Cr13 type mertensite steel Cr17 type mertensite steel

A class steel is used to make bolts above 70 grade (σ_b>700MPa), C class is used to make bolts above 70 grade and which require quenching and tempering treatment, F class is fit for making bolts above 60 grade. 700MPa)

In order to smoothly produce cold upsetting bolts, the chemical components of various stainless steel must be controlled strictly, and some frequently used brands must be implemented according to the regulations in the following table.

Control value for chemical components of cold upsetting steel

Steel brand	Chemical components to be controlled, %
	C	Si	Mn	P	S	Cr	Ni	Mo	Cu	N	Ti
0Cr15(429)	≤0.05	0.30/ 0.50	0.30/ 0.50	≤0.035	≤0.030	14.0/ 16.0	≤0.50	-	-	≤0.025	-
0Cr17(430)	≤0.04	0.30/ 0.50	0.30/ 0.50	≤0.035	≤0.020	16.5/ 17.5	≤0.50	≤0.50	-	≤0.025	-
0Cr17Mo (434)	≤0.04	0.30/ 0.50	0.30/ 0.50	≤0.035	≤0.015	16.5/ 17.5	≤0.50	0.95/ 1.25	-	≤0.025	-
1Cr13(410)	0.09/ 0.15	0.30/ 0.50	0.30/ 0.50	≤0.035	≤0.015	11.5/ 13.5	≤0.50	≤0.50	-	-	-
1Cr17Ni2 (431)	0.15/ 0.20	0.30/ 0.50	0.30/ 0.50	≤0.035	≤0.020	15.5/ 16.8	1.50/ 2.20	≤0.50	-	-	-
0Cr18Ni9 (304)	≤0.05	0.20/ 0.60	1.40/ 1.80	≤0.035	≤0.030	18.0/ 19.5	8.0/ 9.5	-	≤1.00	≤0.06	-
0Cr18Ni9 (304M)	0.03/ 0.05	0.30/ 0.60	1.50/ 2.00	≤0.035	≤0.030	18.0/ 19.2	9.0/ 10.0	-	≤1.00	≤0.06	-
0Cr18Ni9Cu2 (304HC)	≤0.05	0.20/ 0.60	1.50/ 2.00	≤0.035	≤0.030	17.5/ 18.5	8.0/ 9.5	-	1.00/ 3.00	≤0.06	-
0Cr18Ni9Cu3 (304HQ)	≤0.04	0.20/ 0.40	0.60/ 0.90	≤0.035	≤0.030	17.3/ 18.5	9.3/ 10.0	-	3.00/ 4.00	≤0.03	-
0Cr17Ni12 Mo2(316)	≤0.06	0.30/ 0.60	1.40/ 1.80	≤0.035	≤0.030	16.5/ 17.5	10.5/ 13.5	2.00/ 2.45	-	≤0.06	-
00Cr17Ni14 Mo2(316L)	≤0.03	0.40/ 0.70	0.80/ 1.20	≤0.035	≤0.010	17.0/ 18.0	12.5/ 13.0	2.00/ 2.45	-	≤0.03	-
0Cr18Ni12 (305)	≤0.04	0.30/ 0.60	1.50/ 2.00	≤0.035	≤0.030	17.5/ 19.0	11.5/ 13.5	-	≤1.00	≤0.06	-
0Cr16Ni18 (384)	≤0.04	0.30/ 0.60	1.00/ 1.50	≤0.035	≤0.030	15.0/ 17.0	17.0/ 19.0	-	-	≤0.03	-
0Cr18Ni10 Ti(321)	0.04/ 0.06	0.20/ 0.70	1.00/ 1.50	≤0.035	≤0.030	17.2/ 19.0	9.50/ 10.50	-	-	≤0.03	0.40/ 0.70

Recently, the successfully developed super austenite stainless steel, super martensite stainless steel, super ferrite stainless steel, super double phase stainless steel, and martensite aging stainless steel can also be used to produce fastening piece, and the choice shall be made according to detailed service condition.

2. The application of stainless steel in mini type axis.
With the popularization of electrical appliances and the development of office automation, the developing of relevant products like camera, hard disc, soft disc, electrograph, copycat, etc, are very swift. And the requiring quantity of mini motor, driving system coupling shaft , etc, which are related with the above products, have increased accordingly. For the miniaturization of these axis and the requirements of anti-abrasion as well as anti-corrosion, they are commonly made of stainless steel. The important components of mechatronics are often required to be anti-corrosion, high strength, non-magnetic, so under different service conditions, different types of stainless steel should be chosen. The mini axis use martensite and austenite stainless steel, in order to facilitate machining and machining precision, the usage of easy cutting stainless steel is comparatively large. Commonly, austenite stainless steel is used to make the mini axis that require non-magnetic, and martensite stainless steel that can be heat hardened is used to make mini axis that require characters like anti-abrasion, anti-trauma, anti-bending. For the purpose to make austenite stainless steel to achieve the hardness need, commonly use cold machining method to acquire them. The main characteristics of the stainless steel used for mini axis are shown in the table below:

Characteristics of stainless steel used for mini axis

Steel type	Brand	Hardness HV0.5	σb/MPa	Vertical elastic coefficient / MPa	Horizontal elastic coefficient / MPa	magnetic permea- bility (μ)	Thermal expansi- vity (0-100℃) X10-6/K
Martensite stainless steel	3Cr13 Y3Cr13(including S) Y3Cr13(including Pb) 7Cr13Mo 11Cr17	480/620 480/620 480/620 >630 >650	1568/2009 1568/2009 1568/2009 - -	205800 205800 205800 210700 21560	78400 78400 78400 79380 79380	- - - - -	10.4 10.4 10.4 10.1 10.6
Austenite stainless steel	1Cr18Mn8Ni5N Y1Cr18Ni9 Y1Cr18Ni9N 0Cr18Ni9 0Cr19Ni9N 0Cr17Ni12Mo2 0Cr18Ni12N 0Cr17Mn15Ni2N (Japan TN15MH)	>400 200/270 >350 400/550 200/350 200/350 >400 >500	>1274 519/784 >1078 1372/2009 588/1078 588/784 >1372 >1715	196000 191100 191100 191100 191100 191100 191100 188160	71540 68600 68600 68600 68600 68600 68600 68600	>2.5 <1.01 <1.01 >2.5 <1.01 <1.01 <1.01 <1.01	15.7 17.3 17.3 17.3 17.3 16.0 17.0 12.6