Types 304 and 304L
Sheets, Plates, Bars, angles
UNS S30400, 30403
Type 304 Bars, Angles — Pink and White
Type 304L Bars — Pink with Brown Stripe
Type 304 is the basic “18 — 8” chromium-nickel stainless steel. It combines excellent mechanical properties with remarkable resistance to many corrosive agents encountered in domestic and industrial use. It is non-magnetic in the annealedcondition and not hardenable by heat treatment. Both hardness and tensile strength can be increased by cold working. This is an electric-furnace product manufactured to meet the exacting standards of the aircraft industry.
The analysis of Type 304 is similar to that of Type 304L except that Type 304L ismodified by lowered carbon content. This provides good resistance to corrosion in welded construction where subsequent heat treatment is not practicable. Bars and Plates are available not only in the regular Type 304 analysis, but also in an extra low carbon analysis Type 304L. The advantage of this analysis is that it precludes any harmful precipitation in the 800º — 1500ºF range, such as might otherwise occur in welding heavier sections.
SpecificatIons — The following specifications are generally applicable:Sheets & Plates: AMS 5513, ASTM A 167, ASTM A 240Bars: AMS 5639, ASTM A 276, ASTM A 479
Applications — Used where corrosion resistance and good mechanical properties are primary requirements. These grades are widely accepted in such industries as dairy, beverage, and other food products where the highest degree of sanitation and cleanliness is of prime importance. Parts for handling acetic, nitric, and citric acids, organic and inorganic chemicals, dyestuffs, crude and refined oils, etc., are fabricated from this material. Because of its lack of magnetism it is highly desirable for instruments. It is also widely used for architectural trim. Type 304 sheets are used in aircraft applications where corrosion resistance is required, but where gas or arc welding and elevated temperatures are not involved. Type 304L, as noted above, finds particular use in applications requiring welding.
Corrosion Resistance — Types 304 and 304L show good resistance to corrosion. They are highly resistant to strong oxidizing acids, such as nitric acid, and resist attack by a wide variety of organic and inorganic chemicals. Maximum corrosion resistance is obtained in the annealed condition. Intergranular corrosion may occur when material is heated within or cooled through the range of 800º to 1500ºF.
Resistance to ScalIng — Excellent scale resistance at temperatures up to 1600ºF in continuous service. Chromium-nickel grades have a high coefficient of expansion, which should be considered in designing.
Machinability — Types 304 and 304L have a machinability rating of approximately 45% with 1212 rated as 100%. Surface cutting speed on automatic screw machines is approximately 75 feet per minute.
Weldability — Easily welded by all the commercial processes except forging or hammer welding. The resulting weld had good toughness and ductility. Annealing is recommended after welding to maintain maximum corrosion resistance.
ForminG — These grades have very good drawing and stamping properties.
ForginG — Forge between 2100º and 2350ºF. Do not forge below 1700ºF.
Annealing — Annealing range is between 1850º and 2050ºF. Cool rapidly.Water should be used for heavier sections; air for lighter sections. The stress relieving range is between 400º and 750ºF
Types 303S and 303Se — Free Machining
UNS S30300, S30323
Type 303S — Annealed Bars and Pump Shafting: Ends painted Red
High Tensile Bars (Condition B): Ends painted Gray & Orange
Type 303Se — Annealed Bars: Ends painted Purple
High Tensile Bars (Condition B): Ends painted Brown
Type 303 is “18-8” chromium-nickel stainless steel modified by the addition of selenium or sulfur, as well as phosphorus, to improve machinability and non-seizing properties. It is the most readily machinable of all the chromium-nickel grades and has good corrosion resistance. It is non-magnetic in the annealed condition and not hardenable by heat treatment. Tensile strength and hardness can be increased by cold working. It is manufactured by the electric-furnace process and meets the exactingrequirements of the aircraft industry.
SpecfifcatIons — The following specifications are generally applicable: AMS 5640, ASTM A 314, ASTM A 320, ASTM A 582
Applications — Used almost exclusively for parts requiring machining, grinding, or polishing where good corrosion resistance is also required, Its non-seizing and non-galling properties make it ideal for moving parts. Being an austenitic steel, it is useful where low magnetic permeability is desired.
Corrosion Resistance — Because of the elements which are added to improve machinability, Type 303 has slightly less general corrosion resistance than the regular chromium-nickel grades such as Type 304. Maximum corrosion resistance is obtained in the annealed condition.
Resistance to ScalInG — This grade has excellent scale resistance at temperatures up to 1600ºF in continuous service. Like other chromium-nickel grades, it has a high coefficient of expansion which should be considered in designing.
Machinability — Type 303 has considerably better machining characteristics than the other chromium-nickel grades. It has machinability rating of approximately78% with 1212 rated 100%. Surface cutting speed on automatic screw machines is approximately 130 feet per minute.
Weldability — This grade has only fair welding properties.
FormIng — This grade has fairly good forming properties.FoRGInG — Forge between 2100º and 2350ºF. Do not forge below 1700ºF.
AnnealIng — Annealing range is between 1850º and 2050ºF. Cool rapidly. Water should be used for heavier sections; air for lighter sections. The stress relieving range is between 400º and 750º