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Stainless steel plate

Sunmire Steel has a stock of 321 alloys from 3/16 to 3 inches thick。321H(UNS S32109) is the high carbon grade corresponding to 321。The thickness of spot stock is the same as 321。

3/16" 1/4" 5/16" 3/8" 1/2" 5/8" 3/4" 7/8" 1" 1 1/8"
4.8mm 6.3mm 7.9mm 9.5mm 12.7mm 15.9mm 19mm 22.2mm 25.4mm 28.6mm
 
1 1/4" 1 1/2" 1 3/4" 2" 2 1/4" 2 1/2" 2 3/4" 3" 3 1/2" 4"
31.8mm 38.1mm 44.5mm 50.8mm 57.2mm 63.5mm 69.9mm 76.2mm 88.9mm 101.6mm

Alloy 321 (UNS S32100) is a stainless steel with excellent stability。It maintains good resistance to intergranular corrosion at temperatures up to 800-1500°F (427-816°C) and chromium carbide precipitation。Due to the addition of titanium to the composition, 321 alloy can remain stable in the presence of chromium carbide formation。

321 alloy stainless steel has advantages in working at high temperature due to its excellent mechanical properties。Compared with 304 alloy, 321 alloy stainless steel has better ductility and stress-fracture resistance。In addition, 304L can also be used to resist sensitization and intergranular corrosion。

General attributes

Alloy 321 (UNS S32100) is a stainless steel with excellent stability。It maintains good resistance to intergranular corrosion at temperatures up to 800-1500°F (427-816°C) and chromium carbide precipitation。Due to the addition of titanium to the composition, 321 alloy can remain stable in the presence of chromium carbide formation。347 alloy is stable by adding ke and tantalum。.

321 and 347 alloys are commonly used for long-term applications at high temperatures ranging from 800 to 1500°F (427 to 816°C)。If the application involves only welding or heating for a short period of time, 304L should be used instead。

The advantages of 321 and 347 alloys in high-temperature operation also depend on their good mechanical properties。Compared with 304 and 304L, 321 and 347 have better creep stress resistance and stress rupture resistance。This allows these stable alloys to withstand pressures consistent with the ASME Boiler Code and pressure vessel code at higher temperatures。Thus 321 and 347 alloys can be used at a maximum temperature of 1500°F (816°C), while 304,304 L is limited to 800°F (426°C).

321 and Alloy 347 are also available in high carbon varieties with UNS numbers S32109 and S34709 respectively.

化学成分

ASTM A240 and ASME SA-240:

成分

Weight percentage unless otherwise specified,

The maximum value of a column in the table

  321 347
碳* 0.08 0.08
2.00 2.00
0.045 0.045
0.030 0.03
0.75 0.75
17.00-19.00 17.00-19.00
9.00-12.00 9.00-13.00
钶+钽** -- 10 xc minimum 1.00 最大
-- --
钛** Minimum 5 x (C + N) 0.70 最大 --
-- --
0.10 --
The rest The rest
  * H grade carbon content is 0.04 ? 0.10%.

**H grade minimum stabilizers are different formulations。

耐腐蚀性

Uniform corrosion
Alloys 321 and 347 have similar resistance to general corrosion as the unstable nickel-chromium 304。Prolonged heating in the temperature range of chromium carbide levels may affect the corrosion resistance of alloys 321 and 347 in harsh corrosive media。

在大多数环境中,两种合金的耐蚀性差不多;但退火状态下的合金321在强氧化性环境中的耐蚀性稍逊于经退火处理的合金347。Therefore, alloy 347 is superior in water environment and other low temperature environment。Exposure to temperatures in the 800°F -- 1500°F (427°C -- 816°C) range causes the overall corrosion resistance of alloy 321 to be significantly worse than that of alloy 347。Alloy 347 is intended for high temperature applications, where strong resistance to sensitization is required to prevent intergranular corrosion at lower temperatures。

Intergranular corrosion
Alloy 304 and other unstable nickel?Steels are sensitive to intergranular corrosion, and alloys 321 and 347 have been developed for this purpose。

Chromium carbide precipitates at grain boundaries when the unstable chrome-nickel steel is placed in an environment of 800°F -- 1500°F (427°C -- 816°C) or is slowly cooled within this temperature range。Exposed to some highly corrosive medium, these grain boundaries are the first to erode, perhaps weakening the metal and possibly causing complete disintegration。

Intergranular corrosion rarely occurs in organic media or in corrosive water, milk or other dairy products, or in atmospheric conditions, even in the presence of substantial carbide deposits。When welding thinner sheets, the unstable grades are adequate because the temperature range of 800°F -- 1500°F (427°C -- 816°C) is so short that intergranular corrosion is not likely to occur。The degree to which carbides precipitate is harmful depends on the length of time the alloy is exposed to the temperature range of 800°F -- 1500°F (427°C -- 816°C) and the corrosive medium。Thicker plates are welded with carbon content of 0 due to unstable L grade despite longer heating time.03% or lower, carbide precipitation is not enough to cause harm to this grade。

The strong resistance to sensitization and intergranular corrosion of stable 321 and alloy 347 stainless steels are shown in the following table。(Copper-Copper sulphate-16% Sulfuric acid test (ASTM A262, Practice E))。Before the test, the annealed samples from the mill were subjected to a soaking photosensitive heat treatment of 1050°F (566°C) for 48 hours。

Intergranular corrosion test results under long-term sensitization

ASTM A262 Practice E

合金 Rate (ipm) Bend Rate (mpy)
304 0.81 dissolved 9720.0
304L 0.0013 IGA 15.6

*1100°F annealing, 240 hours

Alloy 347 samples did not show intergranular corrosion, indicating that they were not sensitized when exposed to this thermal environment。The low corrosion rates of alloy 321 samples indicate that it has better corrosion resistance than alloy 304L in these environments, although it has suffered some intergranular corrosion。In this test environment, all of these alloys are much superior to the ordinary alloy 304 stainless steel。

In general, alloys 321 and 347 are used for heavy duty welding equipment that cannot be annealed and equipment that operates or cools slowly from 800°F to 1500°F (427°C to 816°C)。Experience gained in a variety of operating conditions provides sufficient information to predict the likelihood of intergranular corrosion in most applications。

Please also review some of our comments in the heat treatment section。

Stress corrosion cracking
Alloy 321 and 347 austenitic stainless steels are sensitive to stress corrosion cracking in halides, similar to alloy 304。This result is due to their similar nickel content。Conditions that cause stress corrosion cracking are :(1) exposure to halide ions (typically chloride), (2) residual tensile stress, and (3) ambient temperatures exceeding 120°F (49°C).。Cold deformation during forming or thermal cycling during welding may cause stress。Stress relief heat treatment after annealing or cold deformation may reduce stress levels。Stable alloys 321 and 347 are suitable for stress-relieved operating environments that may produce intergranular corrosion of unstable alloys。

321 and 347 are particularly useful in environments where unstable austenitic stainless steels, such as alloy 304, are subjected to continuous polysulphuric acid stress corrosion。Exposure of unstable austenitic stainless steel to sensitized temperatures results in chromium carbide precipitation at grain boundaries。When cooled to room temperature in a sulfur-containing environment, sulfides (usually hydrogenated sulfur) react with water vapor and oxygen to form polysulphuric acid at erosion-sensitized grain boundaries。Under the condition of stress and intergranular corrosion, even polysulphuric acid stress corrosion cracking occurs in the oil refining environment where sulphide is ubiquitous。The stable alloys 321 and 347 have solved the problem of cracking by sulphuric acid stress corrosion due to their resistance to sensitization in the heating operating environment。To achieve optimum resistance to sensitization, these alloys should be used under thermal stability if operating conditions can sensitize them。

Spot/gap corrosion
Stable alloys 321 and 347 have similar pitting and gap resistance in the presence of chloride ions to alloys 304 or 304L stainless steel because of their similar chromium content。In general, for unstable and stable alloys, the upper limit of chloride content in aqueous environment is 100 parts per million, especially when there is gap corrosion。Higher chloride content can lead to gap and spot corrosion。In harsh conditions with higher chloride content, lower PH and/or higher temperatures, alloys containing molybdenum such as alloy 316 should be considered。Stable alloys 321 and 347 have passed 100 hours of 5% salt spray test (ASTM B117) without rust and discoloration in the tested samples。However, pitting corrosion, gap corrosion and severe discoloration may occur if these alloys are exposed to salt spray from the ocean。Exposure of alloys 321 and 347 to the Marine environment is not recommended。

抗高温氧化性

The oxidation resistance of 321 and 347 is comparable to other 18-8 austenitic stainless steels。The samples were exposed to high temperatures in the laboratory atmosphere。The scale of rust formation can be calculated by weighing samples periodically from a high temperature environment。The test results are expressed by weight change (mg/cm2), taking the average of the minimum values of the two different samples tested。

Weight change (mg/cm2)
Exposure time 1300°F 1350°F 1400°F 1450°F 1500°F
168 小时
0.032
0.046 0.054
0.067 0.118
500 小时 0.045 0.065 0.108 0.108 0.221
1,000
小时
0.067 -- 0.166 -- 0.338

5,000
小时

-- -- 0.443 -- --

The main difference between 321 and 347 is the fine alloy additive, but does not affect oxidation resistance。Therefore, these test results are representative of both grades。However, oxidation rates are affected by inherent factors such as the exposure environment and product form, and therefore these results should be regarded only as general values for these grades of oxidation resistance。

物理性能

The physical properties of alloys 321 and 347 are similar and, in fact, can be regarded as identical。The values listed in the table apply to both alloys。

If properly annealed, alloy 321 and 347 stainless steels mainly contain austenite and titanium carbide or niobium carbide。Small amounts of ferrite may or may not be present in the microstructure。Small amounts of the Sigma phase may form during prolonged exposure to temperatures between 1000°F and 1500°F (593°C and 816°C)。

热处理 does not harden the stable alloys 321 and 347 stainless steel。

The total heat transfer coefficient of metal depends on other factors besides the thermal conductivity of the metal。In most cases, the film heat dissipation coefficient, rust and metal surface condition。Stainless steel keeps surfaces clean, so it can transfer heat better than other metals with higher thermal conductivity。

Magnetic conductivity
Stable alloys 321 and 347 are generally not magnetic。In the annealed state, its magnetic conductivity is less than 1.02。The permeability will vary with composition and increase with cold cooking。Ferritic welds will have a higher permeability。

物理性能
密度
Grade g/cm3
lb/in3
321 7.92 0.286
347 7.96 0.288
Coefficient of tensile elasticity
28 x 106 psi
193 GPa
Average coefficient of linear thermal expansion
Temperature range  
°C °F Cm/cm ° C In/in ° F
20-100 68 - 212 16.6 x 10-6 9.2 x 10-6
20 - 600 68 - 1112 18.9 x 10-6 10.5 x 10-6
20 - 1000 68 - 1832 20.5 x 10-6 11.4 x 10-6
Thermal conductivity
Temperature range  
°C °F W/m. K Btu, in/hr, ft2•°F
20-100 68 - 212 16.3 112.5
20 - 500 68 - 932 21.4 14.7
比热
Temperature range  
°C °F J/kg K Btu/lb, ° F
0-100 32 - 212 500 0.12
The resistivity
Temperature range  
°C °F Microhm, cm
20 68 72
100 213 78
200 392 86
400 752 100
600 1112 111
800 1472 121
900 1652 126
The melting range
°C °F
1398 - 1446 2550 - 2635

机械性能

Ductility at room temperature
The minimum mechanical properties of stable alloys 321 and 347 chrome-nickel grades in the annealed state (2000°F [1093°C], air-cooled) are shown in the table below。

Ductility at high temperatures
Typical mechanical properties of alloys 321 and 347 at high temperatures are shown in the table below。At 1000°F (538°C) and higher temperatures, the strength of these stable alloys is significantly higher than that of the unstable 304 alloy。

The high-carbon alloys 321H and 347H (UNS32109 and S34700) have higher strength in environments above 1000°F (537°C)。ASME Maximum allowable design stress data for alloy 347H show that the strength of this class is higher than that of alloy 347 with a lower carbon content。Alloy 321H is not permitted for Section VIII applications and, for Section III applications, is limited to temperatures of 800°F (427°C) or below。

Creep and stress rupture properties
Typical creep and stress fracture data of alloy 321 and 347 stainless steels are shown in the table below。The creep and stress fracture strength of stable alloy at high temperature is higher than that of unstable alloy 304 and 304L。The superior properties of alloys 321 and 347 make them suitable for high temperature pressure parts such as our common boilers and pressure vessels。

321 and 347 impact strength
Test temperature Charpy impact energy absorption
°F °C Ft-lb Joules
75 24 90 122
-25 -32 66 89
-80 -62 57 78

ASTM A 240 and ASME SA-240

Minimum required mechanical properties at room temperature
类型

The yield strength
.2% Offset
psi (MPa)

Ultimate tensile strength
psi (MPa)

Elongation (%)

321 30,000
(205)
75,000
(515)
40.0
347 30,000
(205)
75,000
(515)
40.0

ASTM A 240 and ASME SA-240

Minimum required mechanical properties at room temperature

类型 Hardness, maximum
321

217
Brinell

95Rb 95Rb
347 201
Brinell
92Rb 92Rb

Tensile properties at high temperatures

合金 321 (0.036 inches thick / 0.9 mm thick)
Test questions The yield strength
.2% Offset psi
(MPa)
Ultimate tensile strength
psi
(MPa)

% elongation

°F °C
68 20 31,400
(215)
85,000
(590)
55.0
400 204 23,500
(160)
66,600
(455)
38.0
800 427 19,380
(130)
66,300
(455)
32.0
1000 538 19,010
(130)
64,400
(440)
32.0
1200 649 19,000
(130)
55,800
(380)
28.0
1350 732 18,890
(130)
41,500
(285)
26.0
1500 816 17,200
(115)
26,000
(180)
45.0

Tensile properties at high temperature

合金 347 (0.060 inches thick / 1.54 mm thick)
Test temperature The yield strength
.2% Offset psi
(MPa)
Ultimate tensile strength
psi
(MPa)

% elongation

°F °C
68 20

36,500
(250)

93,250
(640)
45.0
400 204 36,600
(250)
73,570
(505)
36.0
800 427 29,680
(205)
69,500
(475)
30.0
1000 538 27,400
(190)
63,510
(435)
27.0
1200 649 24,475
(165)
52,300
(360)
26.0
1350 732 22,800
(155)
39,280
(270)
40.0
1500 816 18,600
(125)
26,400
(180)
50.0

The impact strength
The 321 and 347 have excellent impact toughness both indoors and in sub-zero conditions。The charpy V impact test of annealed alloy 347 after standing at the specified test temperature for one hour is shown in the figure below。Alloy 321 is similar to alloy 347。

Fatigue strength
In fact, the fatigue strength of each metal is affected by the corrosive environment, surface finish, product form, and average stress。For this reason, it is not possible to use an exact number to represent fatigue strength values under all operating conditions。The fatigue limit of alloys 321 and 347 is approximately 35% of their tensile strength

加工

Austenitic stainless steel is considered the easiest alloy steel to weld and can be welded with all fusions, as well as resistance welding。

Two factors are considered when producing welded contacts for austenitic stainless steel: 1) to maintain corrosion resistance and 2) to avoid cracking。

Care must be taken to maintain stable elements in alloys 321 and 347 during welding。Alloy 321 is more likely to lose titanium, whereas alloy 347 is more likely to lose columbium。Avoid carbon from oil and other sources of pollution and nitrogen from the air。Therefore, whether welding good stability of alloy or unstable alloy, should pay attention to keep clean and protect the inert gas。

When welding austenitic metal structure, it is easy to split during operation。For this reason, alloys 321 and 347 need to add a small amount of ferrite to minimize crack sensitivity during resolidification。Stainless steels containing columbium are more prone to hot cracking than those containing titanium。

The matching filler metal can be used for welding stable steels such as alloy 321 and 347。The matching filler metal of alloy 347 can sometimes also be used for welding of alloy 321。

These stable alloys can be added to other stainless or carbon steels。Alloy 309 (23% Cr-13.5% Ni) or nickel based filler metals can be used for this purpose。

热处理

Alloys 321 and 347 are annealed at temperatures ranging from 1800 to 2000°F (928 to 1093°C)..。Although the primary purpose of annealing is to enhance the softness and ductility of the alloy, stress can be relieved without intergranular corrosion in the carbides precipitation range of 800 -- 1500°F (427 to 816°C)。Although prolonged heating at this temperature may reduce the general corrosion resistance of the alloy to some extent,Alloys 321 and 347, however, relieved stress after several hours of annealing at temperatures ranging from 800 to 1,500 °F (427 to 816°C),And its general corrosion resistance is not significantly reduced。As emphasized, low temperature annealing in the range 800 ---- 1500°F (427 to 816°C) does not result in intergranular corrosion。

High annealing temperatures of 1800 to 2000°F (928 to 1093°C) are recommended for optimum ductility.。

When you put the nickel?When stainless steel is processed into equipment that requires maximum protection against chromium carbide precipitation, it is important to recognize that columbium is not as stable as titanium。For these reasons, the degree of stability and protection resulting from the application of alloy 321 is not so obvious。

When corrosion resistance is required to be maximized, 321 alloys must be treated with stable annealing。Heat at 1550 to 1650°F (843 to 899°C) for up to 5 hours, depending on thickness。This temperature range exceeds the temperature range at which chromium carbide is formed and is sufficient to decompose and dissolve previously formed chromium carbide。In addition, at this temperature, titanium can combine with carbon to form a harmless titanium carbon。As a result,?Reduced to a solid solution, the carbon is forced to combine with titanium to form harmless carbides。

The stable alloy 347 containing columbium does not require this additional treatment as often。

After heat treatment in an oxidizing environment, the annealed oxide is removed to a derusting solution, such as a mixture of nitric and hydrofluoric acid。After removing rust, the surface of stainless steel should be thoroughly washed to remove residual acidic solution。

These alloys cannot be hardened by heat treatment。

清洁
Regardless of corrosion, stainless steel surfaces should be kept clean during use and manufacture, even under normal working conditions。

During welding, inert gas processing is adopted. Rust and slag formed during welding are removed by stainless steel brush。A normal carbon steel brush will leave carbon steel particles on the surface of stainless steel, which will eventually cause the surface to rust。In the case of strict requirements, the welding area should be treated with a derusting solution (such as nitric acid and hydrofluoric acid mixed solution) to remove rust and slag. After derusting, the stainless steel surface should be thoroughly washed to wash away the residual acidic solution。

Inland, light industrial materials require less maintenance, with only sheltered areas sometimes needing to be cleaned with pressurized water。Heavy industry recommends frequent cleaning to remove accumulated dust, which can eventually cause corrosion and damage the surface appearance of stainless steel。

Proper design facilitates cleaning。With rounded Angle, inner rounded Angle, seamless equipment, is conducive to cleaning and surface polishing。

Reference data are typical analyses only and should not be used as a maximum or minimum for specifications or final products。Data for a specific piece of material may be inconsistent with the above reference data。