Archives

Duplex Stainless Steels

The alloy is a mixture of austenite and ferrite in their structure. They show characteristics of both phases with higher strength and ductility. Nitrogen is added to the second-generation duplex alloys and provides increased strength and weldability. AK Steel’s 19d NITRONIC® cyclic oxidation is good, high strength and excellent stress corrosion resistance, and the 2205 alloy provides very good pitting and uniform corrosion resistance, high strength and high resistance to stress corrosion cracking. Quality stainless steel manufacturing, from heat to heat and year to year claims, precise control of raw material ingredients and melting practices.

Exact quantities of scrap and alloying elements to deliver presorted the melting furnaces so that the heats or lots to be within the ranges specified composition. Among the composition usually ranges from a group of chemical elements for each grade stainless steel. Besides the visual appeal of polished stainless, some of functionsserved at stainlesssurfaces properly prepared. And sanitary applications, polished stainless steel not only looks clean, but also easy to clean and keep clean.

There are also economic considerations in specifying Nish. For example, bright annealed cold rolled nish may be speci ed in the No. 8 polished nish more expensive or some might proprietary nishes rolled serve the same purpose as the No. 4 polished nish. Information on? Nishes sometimes resulting in signi Cant savings.

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Precipitation-Hardening Stainless Steels

There are two general areas PH grade stainless steels; martensitic and semi-austenitic. The group includes martensitic 17-4 and 15-5 chromiumnickel PH® PH® with columbium and copper additions. They develop a high strength and hardness by heat treatment, which precipitates the copper. The PH martensitic steels used in aerospace, chemical and petrochemical, and food processing applications. The semi-austenitic grade PH® 17-7 and 15-7 PH Mo®.

They are in the state annealed austenitic, martensitic condition but hardened. 17-7 PH stainless high strength and excellent fatigue properties, and used in aerospace components. PH 15-7 Mo stainless used in applications requiring high strength and hardness, such as keeping rings, springs and aircraft bulkheads. Surface? An important component in any application or buy a specified order?

Stainless steel regardless of the intended end use nish. And, for those applications where appearance is important ,? Nish is a design element and must be speci? Ed. In architecture or other visible applications, the appearance of stainless steel and specified critical design element? Request the wrong? Can change the e nish needed? Ect. In consumer products, the gleam of a polished stainless steel strong sales appeal. In institutional kitchen, restaurant, and hospital applications, properly helps? Stainless given to emphasize the feeling of cleanliness.

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General Properties of Martensitic Stainless Steels

Allegheny Ludlum Types 410, 420, 425 Modified, and440A (see composition on Page 2) are hardenable,straight-chromium stainless steels which combine superior wear resistance of high carbon alloys with theexcellent corrosion resistance of chromium stainlesssteels. Oil quenching these alloys from temperaturesbetween 1800°F to 1950°F (982-1066°C) producesthe highest strength and/or wear resistance as well ascorrosion resistance. A range of as-quenched hardnessis achieved in these alloys by varying the carbon levelfrom 0.15% maximum in Type 410 to 0.60-0.75% inType 440A.

A major use for these grades of heat treatable stain-less steels is in cutlery. Depending on the customer’send-use requirements, cutlery alloys are usuallyselected with respect to heat treating response, mechanical properties and fabricating characteristics.When sufficient amounts of carbon are added to straight- chromium stainless steels, the alloy then hasthe capability to transform its microstructure through proper heat treatment (hardening) into one that willpossess optimum strength, hardness, edge retention,and wear resistance. The presence of sufficientchromium will impart the necessary corrosion resis-tance and form chromium carbide particles thatenhance the wear resistance of the given alloy. The higher the carbon content, the greater the amount of chromium carbide particles, and the greater thestrength and hardness for heat treatable straight-chromium stainless steels.

When blanking cutlery parts from annealed raw mate-rial stock, Types 410, 420, and their higher carbonversions (Types 410HC and 420HC) will usually exhibithardness, yield strength, and tensile strength that arelow enough for fine blanking purposes. However, Type440A is not readily amenable to fine blanking due to itshigher strength and hardness in the annealed condition;and therefore, could require more powerful presses toblank parts. In addition, the presence of large primarycarbides in Type 440A would tend to reduce die life.

When buffing blanked parts, the higher hardness of Type 440A in the heat treated condition (hardened)would mean less residual buffing lines on the surfacesof parts but the large primary carbides could be dis-lodged during buffing which would produce scratchescalled “comet-tails”. Stainless steels lower in carboncontent are essentially free of “comet-tails”. Other applications for these grades include dental andsurgical instruments, nozzles, valve parts, hardenedsteel balls and seats for oil well pumps, separatingscreens and strainers, springs, shears, and wearsurfaces.

These alloys are used where strength, hardness, and/or wear resistance must be combined with corrosionresistance.

These alloys are available as plate, sheet, strip and flat bars.

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