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Each of the stainless steel ‘families’ or types, (ferritic, martensitic, austenitic, duplex and precipitation hardenable, (PH)), are described in more detail than SSAS 1.1. The atomic, (crystallographic), structures body centred cubic, (bcc), and face centred cubic, (fcc), cover ferritic and austenitic types, respectively. The chromium ranges, mechanical strength, and magnetic properties are compared and examples of grades for each type of stainless steel given. These include 1.4003, (3Cr12), 1.4016, (430), ferritic, 1.4028, (420S45), 1.4057, (431), 1.4418, (248SV), martensitics, 1.4301, (304/304S31), 1.4307, (304L/304S11), 1.4401, (316/316S31), 1.4404, (316L/316S31), austenitics, 1.4460, (2205 / 318S13), 1.4501, duplex and 1.4542, (17/4PH 17/4 17-4) and 1.4594, (520B) precipitation hardenable grades.
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The compositions, (chemical analysis), of cutlery and holloware steel types 18/8, (18.8 or 18-8), 18/10, (18.10 or 18-10) and 18/0 are described. The use of these austenitic and ferritic stainless steels for cutlery is briefly outlined and compared to the martensitic stainless steels. LAST UPDATED 1st February 2001
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A summary of the EN standards for stainless steel products showing which grades appear in which standards.
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Ferritic stainless steels are magnetic, have a low carbon content and contain chromium as the main alloying element, typically between 13% and 17%. Examples of ferritic grades are 3Cr12, (1.4003) and 430, (1.4016).
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Sulphur, selenium and calcium treated improved machinability stainless steels are compared. European steel numbers for these grades are listed and include 1.4005, 1.4006, 1.4021, 1.4028, 1.4029, 1.4031, 1.4057, 1.4112, 1.4125, 1.4542, 1.4305, 1.4307, 1.4541, 1.4401 and 1.4404. The former BS grades covered by this article include 416S21, 416S29, 416S37, 416S41, 441S29, 441S49, 303S21, 303S41, 325S21 and 326S36 Grade types 440B, 440C and 17/4PH, 17/4, 17-4 are also mentioned. The short-comings of these types of steels, compared to the un-treated types is outlined.
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The main factor in the selection process for stainless steels is corrosion resistance. Careful consideration of the application should be done to enable a choice of grade with suitable corrosion resistance whilst keeping costs to an economic minimum. Other considerations such as mechanical properties, (strength and toughness), physical properties, (magnetic permeability), and forming, fabrication and joining methods available should be secondary. (91)
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This article has a listing of terms often specifically associated with stainless steels, their processing and use. Terms listed include, active, annealing, austenite, austenitising, bright annealing, cathodic protection, chlorides, (halides), cold and hot working, corrosion, creep, deep drawing, duplex, fatigue, (endurance), ferrite, martensite, normalising, passive, passivation, permeability, pH, pickling, pinch pass, pitting, precipitation hardening, scaling temperature, sensitisation, stabilisation, stress relieving, stretch forming and tempering
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Martensitic stainless steels are magnetic. Their main alloying elements are chromium, (typically 18%), and carbon, They are used for strength and moderate corrosion resistance. Examples of martensitic grades are 410, 410S21, (1.4006), 420, 420S29, (1.4021), 431, 431S29, (1.4057) and 440C, (1.4125).
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Guidance on methods for sorting stainless steels from low alloy and carbon steels is shown. These include physical, (colour, density, magnetic), and mechanical, (hardness), properties and chemical tests, (copper sulphate, copper chloride, nitric acid and sulphur tests). A suggested approach to a step-by-step procedure for differentiating stainless steels from carbon steels is tabulated. These methods have not been verified by the BSSA, who take no responsibility for their accuracy of the conclusions reached on steel types.
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A summary of datasheets for tubular products
