P,S,Si... Etc Effect on Stainless Steel

7/27/2019 P,S,Si... Etc Effect on Stainless Steel

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STAINLESS STEEL INFO

What you need to know(Probably more then you ever wanted to know! )

The following is a discussion of the various types of stainless steel. For otherterms and their definitions you will encounter when dealing with stainless steel

click here.

18-8:300 series stainless steel having approximately (not exactly) 18% chromium and 8%nickel. The term "18-8" is used interchangeably to characterize fittings made of 302, 302HQ, 303,

304, 305, 384, XM7, and other variables of these grades with close chemical compositions. There

is little overall difference in corrosion resistance among the "18-8" types, but slight differences in

chemical composition do make certain grades more resistant than others do against particularchemicals or atmospheres. "18-8" has superior corrosion resistance to 400 series stainless, is

generally nonmagnetic, and is hardenable only by cold working.

304:The basic alloy. Type 304 (18-8) is an austenitic steel possessing a minimum of 18%chromium and 8% nickel, combined with a maximum of 0.08% carbon. It is a nonmagnetic steel

which cannot be hardened by heat treatment, but instead. must be cold worked to obtain higher

tensile strengths.The 18% minimum chromium content provides corrosion and oxidation resistance. The alloy's

metallurgical characteristics are established primarily by the nickel content (8% mm.), which also

extends resistance to corrosion caused by reducing chemicals.

Carbon, a necessity of mixed benefit, is held at a level (0.08% max.) that is satisfactory for mostservice applications.The stainless alloy resists most oxidizing acids and can withstand all ordinary rusting.

HOWEVER, IT WILL TARNISH. It is immune to foodstuffs, sterilizing solutions, most of the

organic chemicals and dyestuffs, and a wide variety of inorganic chemicals. Type 304, or one of

its modifications, is the material specified more than 50% of the time whenever a stainless steel is

used.Because of its ability to withstand the corrosive action of various acids found in fruits, meats,

milk, and vegetables, Type 304 is used for sinks, tabletops, coffee urns, stoves, refrigerators, milk

and cream dispensers, and steam tables. It is also used in numerous other utensils such as cooking

appliances, pots, pans, and flatware.Type 304 is especially suited for all types of dairy equipment - milking machines, containers,

homogenizers, sterilizers, and storage and hauling tanks, including piping, valves, milk trucks and

railroad cars. This 18-8 alloy is equally serviceable in the brewing industry where it is used in

pipelines, yeast pans, fermentation vats, storage and railway cars, etc. The citrus and fruit juiceindustry also uses Type 304 for all their handling, crushing, preparation, storage and hauling

equipment.In those food processing applications such as in mills, bakeries, and slaughter and packing houses,

all metal equipment exposed to animal and vegetable oils, fats, and acids is manufactured from

Type 304.Type 304 is also used for the dye tanks, pipelines buckets, dippers, etc. that come in contact with

the lormic, acetic, and other organic acids used in the dyeing industry.
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In the marine environment, because of it slightly higher strength and wear resistance than type

316 it is also used for nuts, bolts, screws, and other fasteners. It is also used for springs, cogs, and

other components where both wear and corrosion resistance is needed.

Type Analysis of Stainless Type 304Carbon 0.08% max. Silicon 1.00% max.

Manganese 2.00% max. Chromium 18.00-20.00%

Phosphorus 0.045% max. Nickel 8.00-10.50%

Sulfur 0.030% max.

316:

For severe environments. Of course, there are many industrial processes that require a higher level

of resistance to corrosion than Type 304 can offer. For these applications, Type 316 is the answer.

Type 316 is also austenitic, non-magnetic, and thermally nonhardenable stainless steel like Type304. The carbon content is held to 0.08% maximum, while the nickel content is increased slightly.

What distinguishes Type 316 from Type 304 is the addition of molybdenum up to a maximum of

3%.Molybdenum increases the corrosion resistance of this chromium-nickel alloy to withstand attack

by many industrial chemicals and solvents, and, in particular, inhibits pitting caused by chlorides.

As such, molybdenum is one of the single most useful alloying additives in the fight against

corrosion.By virtue of the molybdenum addition, Type 316 can withstand corrosive attack by sodium and

calcium brines, hypochlorite solutions, phosphoric acid; and the sulfite liquors and sulfurous acids

used in the paper pulp industry. This alloy, therefore, is specified for industrial equipment that

handles the corrosive process chemicals used to produce inks, rayons, photographic chemicals,

paper, textiles, bleaches, and rubber. Type 316 is also used extensively for surgical implants

within the hostile environment of the body.Type 316 is the main stainless used in the marine environment, with the exception of fastenersand other items where strength and wear resistance are needed, then Type 304 (18-8) is typically

used.

Type Analysis of Stainless Type 316:

Carbon 0.08% max. Silicon 1.00% max.

Manganese 2.00% max. Chromium 16.00-18.00%

Phosphorus 0.045% max. Nickel 10.00-14.00%

Sulfur 0.030% max. Molybdenum 2.00-3.00%

We've added this more basic breakdown that includes just about every other grade of

stainless steel we've heard of:

Other Types of Stainless and grades:

Austenitic:Type 301 contains less chromium and nickel than 302 for more work hardening.


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Type 302 is the basic type of the 300 series, 18% chromium8% nickel group. It is the

renowned 188Stainless and is the most widely used of the chromium nickel stainless and heat resisting steels.

Type 303 contains added phosphorus and sulfur for better machining characteristics.Corrosionresistance is slightly less than 302/304.

Type 303Se contains Se and P added to improve machinability.

Type 305 has increased nickel to lower work hardening properties.

Type 309309Shave added chromium and nickel for more corrosion resistance and high

temperature scaling resistance. 309S contains less carbon to minimize carbide precipitation.

Type 310310Shave higher nickel content than 309309Sto further increase scaling

resistance.310S contains less carbon than 310 to minimize carbide precipitation.

Type 321 contains titanium to tie up the carbon and avoid chromium carbide precipitation inwelding.

Type 330 ultra high nickel content provides best corrosion resistance to most furnaceatmospheres. This grade has low coefficient of expansion, excellent ductility and high strength.

Type 347348 have columbium tantalum added to tie up the carbon and avoid chromium

carbide precipitation in welding. Use for temperatures from 800to 1650 degrees F.

Ferritic:

Type 405 contains 12% chromium with aluminum added to prevent hardening.

Type 430 is the basic type in the ferritic group, possessing good ductility and excellent resistanceto atmospheric corrosion. Its scaling resistance is higher than 302 in intermittent service,

somewhat lower in continuous use.

Type 430F430Sehave sulfur and selenium (respectively) added for increased machinability.

Type 442 has added chromium for improved resistance to scaling.

Type 446 has still higher chromium content (27%) for added scaling resistance and is highest ofthe standard straight chromium types. Alloys with over 30% chromium become too brittle to

process.

Martensitic:


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Type 410 is the basic Martensitic type. It is the general purpose corrosion and heat resisting

chromium stainless steel. It can be hardened by thermal treatment to a wide range of mechanicalproperties. It can be annealed soft for cold drawing and forming. This grade is always magnetic.

Type 403 is a special high quality steel made for blades and buckets for steam turbine andjetengine compressors. This grade is eminently suited for very highly stressed parts. Thismaterial is magnetic in all conditions.

Type 416416Seare modifications of Type 410, being the free machining, nonseizing, nongalling alloys. These

properties are obtained by the addition of sulfur or selenium to Type 410.This is a heat treatable

grade with corrosion resistance and other characteristics closely approaching those of Type 410.

Type 420 is a chromium stainless steel capable of heat treatment to a maximum hardness of

approximately 500 Brinell. It has a maximum corrosion resistance only in the fully hardened

condition. Type 420 is magnetic in all conditions.

Type 431 is a nickel bearing (1.252.00%)chromium stainless steel which may be heat treated to

high mechanical properties. It is magnetic in all conditions of use. It has superior corrosion

resistance to Types 410, 416, 420, 430 and 440 stainless steels.

Type 440C is the stainless steel that can be heat treated to the highest hardness of any of the

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P,S,Si... Etc Effect on Stainless Steel