Stainless steel grade numbers identify the quality, durability, and the temperature resistance. The numbers associated with stainless steel grades and types also refer to the amount of Chromium, Nickel, Iron, Manganese, Titanium, etc, that make up the grade. For example, the number 316 contains 16%-18% Chromium and 11%-14% Nickel. The number 18/10 identifies the composition ratio of the stainless steel. These numbers refer to the amount of Chromium and Nickel percentages 18% and 10%. Stainless steel is used when corrosion and or oxidation is possible. A minimum of 12% Chromium lowers oxidation and corrosion resistance to the steel. Steel and the ferrous alloys within it will have a minimum of 12% Chromium for the resistance of corrosion, therefore is considered “Stainless Steel”. NOTE: Stainless Steel 304 is the most common. The main component of stainless steel is Iron, Chromium, and Nickel.
Highly ductile for formed products and hardens rapidly during mechanical process.
-Has better wear resistance and fatigue strength than type 304.
Free machining version of type 304.
-Has the addition of sulfur and phosphorus.
The most common of austenitic grades which contain 8% nickel and 18% chromium.
-Used for chemical processing equipment, food industries, and beverage industries.
Contains 11% to 14% nickel and 16% to 18% chromium.
-Also has molybdenum added to the nickel and chrome of the 304 and the molybdenum is used to control “pit type attack”.
-Used in chemical processing, the pulp and paper industry, for food and beverage processing.
Contains higher percentage of molybdenum than 316 for high corrosive environments.
-Must have a minimum of 3% molybdenum.
-It is mostly used in stacks that contain scrubbers.
Developed for corrosive resistance to repeated exposure to temps above 800 degrees fahrenheit.
-321 is made by the addition of titanium.
-347 is made by the addition of tantalum and columbium.
-321 and 347 types are used primarily in the aviation industry.
Lower chromium amount and added aluminum.
-Prevents hardening when cooled from high temps.
Lowest chromium content of all stainless steels.
-Originally designed for muffler stock.
-Used for exterior parts in non critical corrosive environments.
Has the basic martensitic grade and contains the lowest alloy content.
-General purpose and heat treatable stainless steel.
-Used when corrosion is not severe.
-Applications include stressed parts needing strength and corrosion resistance.
Contains a lower carbon amount than Type 410.
-Improved weldability but lower harden ability.
-A general purpose corrosion and heat resisting chromium steel.
Has 2% nickel added for improved corrosion resistance.
-Applications include various springs and kitchen cutlery.
Has added phosphorus and sulphur to improve machinability.
-Applications include screws and machine parts.
Has more carbon to improve mechanical properties.
-Applications include medical and surgical instruments.
A basic ferritic grade with less corrosion resistance than 304.
-430 has high resistance to corrosives.
Has increased chromium for better corrosion resistance.
-Applications used in high strength parts (valves & pumps).
Has molybdenum added for improved corrosion resist.
-Applications include automotive industry trims and metal fasteners.
Type 436 has columbium added in for better corrosion and heat resist.
-Applications include deep drawn parts.
More chromium and carbon added to improve toughness and corrosion resist.
Has more chromium to improve scaling resistance.
-Applications included are “heat” parts for furnaces and heaters.
Has more chromium introduced to improve corrosion at high temps.
-Best for oxidation resistance in a sulfuric atmosphere.
-17% chromium and 4% nickel.
Austenitic steels strengthened by hot and cold work.
Austenitic superalloys = All grades but alloy 661 are strengthened by second phase precipitation.
Carbon steels and alloy steels are designated a four digit number.
-The first digit indicates the main alloying element.
-The second digit indicates the secondary alloying element.
-The last two digits indicate the amount of carbon, in hundredths of a percent by weight.
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