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Stainless steel plate

317LMN (UNS S31726) alloy is an austenitic stainless steel based on molybdenum, which has strong resistance to chemical erosion。In addition, compared with conventional stainless steel, 317MN alloy has higher ductility, stress fracture resistance and higher compressive strength at high temperature。It is low carbon grade or L grade, which has resistance to sensitization during welding and heat treatment。M and N refer to higher molybdenum and nickel contents, respectively。Molybdenum and nickel content makes it highly resistant to pitting and crevice corrosion, especially in high temperature solutions containing acid, chloride and sulfur compounds。Nitrogen increases its strength。This stainless steel alloy has the highest resistance to water corrosion of all the standard grades of stainless steel。Same as 321。

3/16" 5/16" 3/8" 1/2" 5/8" 3/4"
4.8mm 7.9mm 9.5mm 12.7mm 15.9mm 19mm
 

般属性

Alloys 317LMN and 317L are molybdenum-containing austenitic stainless steels with better chemical resistance than conventional chrome-nickel austenitic stainless steels such as alloy 304。In addition, 317LMN and 317L alloys exhibit greater fracture stress strength and better ductility than conventional stainless steel at high temperatures。All are low carbon grade or "L" grade and provide resistance to sensitization during welding and other heat treatment processes。"M" and "N" denote incremental molybdenum and nitrogen in the composition。The combination of molybdenum and nitrogen improves pitting and gap resistance, especially at high temperatures containing acidic compounds, chlorides and sulfides。Nitrogen also contributes to the strength of these alloys。Both alloys are designed for harsh operating environments such as FGD systems。

化学成分

化学成分 percentage by weight
成分 Type 317L Type 317LMN
0.03 maximum 0.03 maximum
2.00 2.00
0.A maximum of 75 0.A maximum of 75
18.00 - 20.00 17.00 - 20.00
11.00 - 15.00 13.50 - 17.50
3.00 - 4.00 4.00 - 5.00
0.04 maximum 0.04 maximum
0.03 maximum 0.03 maximum
0.A maximum of 10 0.10 - 0.20
The rest The rest
UNS No. S31703 S31726

耐腐蚀

317 l and alloy317LMNStainless steel is more resistant to atmospheric and other mild corrosion than conventional chrome-nickel stainless steel。In general, an environment that is not corrosive to 18Cr-8Ni steel will not corrode alloys containing molybdenum, except for strongly oxidizing acids such as nitric acid。

合金317LMNAnd 317L stainless steel is more resistant to sulfuric acid solution corrosion than conventional chromium-nickel stainless steel。The corrosion resistance of the alloy increases with the increase of molybdenum composition。These alloys are resistant to sulphuric acid concentrations up to 5% at temperatures up to 120°F (49°C)。At temperatures below 100°F (38°C), these alloys exhibit excellent corrosion resistance against higher concentration solutions。However, application testing should consider specific operational factors that may influence corrosion behavior。These alloys are more resistant to concentrated gas than conventional alloy 316 during the process of concentrated gas。The concentration of acid has a significant influence on the rate of corrosion in such environments, and a careful decision should be made based on specific application tests。

The table below is annealed317LMNAnd 317L samples in a variety of solutions relevant to the processing industry and ASTM tests。This table lists the relative data of alloy 316L and alloy AL276 for comparison。

Corrosion resistance in boiling solutions and ASTM tests
The test solution Corrosion rate (mm/y)
Alloy
316L
Alloy
317L
Alloy
317LMN
Alloy
276
20%
乙酸
0.12
(<0.01)
0.48
(0.01)
0.12
(<0.01)
0.48
(0.01)
45%
蚁酸
23.41
(0.60)
18.37
(0.47)
11.76
(0.30)
2.76
(0.07)
10%
草酸
48.03
(1.23)
44.90
(1.14)
35.76
(0.91)
11.24
(0.28)
20%
磷酸
0.06
(0.02)
0.72
(0.02)
0.24
(<0.01)
0.36
(0.01)
10%
硫酸
635.7
(16.15)
298.28
(7.58)
157.80
(4.01)
13.93
(0.35)
10%
Sodium bisulfate
71.57
(1.82)
55.76
(1.42)
15.60
(0.40)
2.64
(0.07)
50%
Sodium hydroxide
77.69
(1.92)
32.78
(0.83)
85.68
(2.18)
17.77
(0.45)
ASTM A262
Practice B
(FeSO4H2SO4)
26.04
(0.66)
20.76
(0.53)
17.28
(0.44)
264.5
(6.72)
ASTM A262
Practice C
(65% HNO3)
22.31
(0.56)
19.68
(0.50)
16.32
(0.42)
908.0
(23.06)
ASTM A262
Practice E
(Cu, CUSO4•H2SO4)
合格 合格 合格 合格

These alloys have a low carbon content (less than 0.03%) effectively prevent the alloy in the process of heat treatment (such as welding or forging) sensitization phenomenon caused by intergranular corrosion。317LMNAnd alloy 317L stainless steel has higher chromium content, with stronger resistance to intergranular corrosion。It should be noted that intergranular corrosion resistance may be impaired by prolonged exposure to 800 -- 1400°F (427 -- 816°C) and that precipitation in the Sigma phase may also make them brittle。317LMN alloy has higher nitrogen content and can slow down the precipitation of Sigma phase and carbide。

Pitting equivalent
合金 PRE
Alloy 316
25
Alloy 317L 30
317LMN 38
Alloy 625 52
Alloy C276 69

As shown in the above pitting equivalent (PRE) table, high molybdenum and nitrogen content can greatly improve pitting resistance。PRE was derived from corrosion test results。Corrosion tests show that nitrogen is 30 times more effective than chromium and about 9 times more effective than molybdenum in improving the pitting resistance of chloride。

The initial gap corrosion temperature specified in the modified ASTG-48B test is a valid method for comparing the corrosivity of stainless steel and nickel-based alloys。The following critical gap corrosion temperature chart shows that the resistance of austenitic stainless steel to gap corrosion increases with the increase of molybdenum and nitrogen content in the alloy。

Simulation of gap corrosion in FGD system
合金 Weight loss (g/cm2)
24°C
(75°F)
50°C
(122°F)
70°C
(158°F)
Type 317L
0.0007
0.0377
0.0500
317LMN 0.0000 0.0129 0.0462
Alloy 625 0.0000 0.0000 0.0149
Alloy C276 0.0000 0.0001 0.0004

* 72 hours of exposure according to ASTM G-48B procedures to the following solutions:
7 vol.%H2SO4, 3 vol%HCI, 1 wt% CuCl2, 1 wt%FeCl3

抗氧化

Chromium-nickel-molybdenum steels have excellent oxidation resistance and low scale formation rates at temperatures not higher than 1600-1650°F (871-899°C) in the ordinary atmosphere。

加工

317LMNAnd alloy 317L stainless steel has similar physical and mechanical properties to conventional austenitic stainless steel, so it can be processed in the same way as alloy 304 and 316。

热处理

锻造
The recommended initial temperature range is 2100 -- 2200°F (1150-1205°C) and the end temperature range is 1700 -- 1750°F (927-955°C).。

退火
317LMNAnd alloy 317L stainless steel can be annealed in the temperature range 1975-2150°F (1080-1175°C), followed by either gas cooling or water quenching, depending on the thickness。The sheet shall be annealed at an environment between 2100°F (1150°C) and 2150°F (1175°C)。The metal is cooled from annealing temperature in 3 minutes。

硬化
These grades cannot be hardened by heat treatment。

焊接

It is recommended to use superalloy materials that can maintain corrosion resistance under welding conditions as fillers。It is recommended to weld alloy 317L with a filler metal of not less than 6% molybdenum and 317LMN with a filler metal of not less than 8% molybdenum, such as alloy 625。In applications where superalloy materials cannot be used as filler metals or where post-weld annealing or pickling is not possible, the harshness of the operating environment should be carefully considered to determine the feasibility of using gas welds (welds made without filler)。The best corrosion resistance of gas welded 317LMN and alloy 317L stainless steel can be obtained by annealing and pickling after welding。For more information, refer to ASTM A-380, "Recommended Practice for Descaling and Cleaning of Steel Surfaces"。

机械性能

ASTM minimum tensile properties and maximum hardness standards for annealed sheet, sheet, and strip products are shown below:

Minimum mechanical performance standards specified in ASTM A-240
性能 Type 317L 317LMN
Ultimate tensile strength KSi (MPa)
75
(515)
80
(550)
0.2% yield strength KSi (MPa) 30
(205)
35
(240)
Elongation 2" (5.1 cm) 40 40
Maximum hardness 217BHN --
UNS No. S31703 S31726

物理性能

The physical properties data in the table below represent the iron - Chromium - nickel - molybdenum stainless steel grades。In fact, these data are applicable to both 317LMN and alloy 317L stainless steel。All properties are room temperature (20°C, 68°F) unless otherwise noted。

密度
0.29
8.0
lb/in3
g/cm3
Modulus of elasticity 29•106
200
psi
Gpa
The melting range 2410 to 2550
1320 to 1400
° F
°C
Thermal conductivity
    68 to 212 ° F
    20 to 100 ° C
100.8
14.6
Btu/ft2- hr - ° F - in
Watts/m- K
Coefficient of thermal expansion
77 ° F (25 ° C) to:     
    212°F (100°C)
    932°F (500°C)
    1832°F (1000°C)
9.2 (16.5)
10.1 (18.2)
10.8 (19.5)
10-6/°F (10-6/°C)
10-6/°F (10-6/°C)
10-6/°F (10-6/°C)
比热 0.11
0.46
Btu/lb - ° F
J/g ° K
The resistivity 31.1
0.79
(including - ohm - in
(including - ohm - in

Complete annealing of permeability
    0.5" 板材
    65% 冷作
    0.5"板材


1.0028

1.0028

µ AT H = 200 oe

µ AT H = 200 oe