STEEL FABRICATION - SSINA

1 STAINLESS STEELFABRICATIONHANDBOOKDESIGNERS tainlessSteelTheValueOption 3819 FABRICATION 6/22/01 2:57 PM Page 3 TABLE OF of Stainless STEEL ..2 FABRICATION Properties ..2 Drilling ..4 Blanking, Punching, and Nibbling ..5 Abrasive Cutting ..6 Arc Cutting ..7 Plasma Arc ..8 Types ..9 Press Brakes ..9 Roll ..10 Removal of Oxide Solutions .. of Weld Discoloration ..10 Passivation ..10 Finishing ..11 Grinding, Polishing & in the .. Specialty STEEL Industry of NorthAmerica ( SSINA ) and the individual companies it represents have madeevery effort to ensure that the informationpresented in this handbook is technicallycorrect.

2 However, neither the SSINA norits member companies warrants theaccuracy of the information contained in this handbook or its suitability for anygeneral and specific use. The SSINA assumes no liability or responsibility ofany kind in connection with the use ofthis information. The reader is advisedthat the material contained herein shouldnot be used or relied on for any specificor general applications without firstsecuring competent 1 GENERALS tainless STEEL is not a single alloy, but rather the name applies to a group of ironbased alloys containing a minimum of chromium. Other elements are added andthe chromium content increased to improve the corrosion resistance, improve heat resist-ing properties, enhance mechanical properties, and/or to improve fabricating characteris-tics.

3 There are over 50 stainless STEEL grades that were originally recognized by theAmerican Iron and STEEL Institute (AISI) and are detailed in a designer handbook, DesignGuidelines for the Selection and Use of Stainless STEEL , available from the Specialty SteelIndustry of North America ( SSINA ).This booklet on the FABRICATION of stainless STEEL will only deal with 30 of the more com-mon grades in three metallurgical groups: austenitic, ferritic, and GROUPThis group contains chromium and nickel and is identified by the Type 300 containing chromium, nickel, and manganese are Type 200. These two typeshave different compositions and properties, but many common characteristics.

4 Theycan be hardened by cold working, but not by heat treatment. In the annealed condition,all are essentially nonmagnetic. They have excellent corrosion resistance and unusuallygood formability. Type 304 (18% chromium - 8% nickel) and Type 316 (16% chromium -10% nickel - 2% molybdenum) are the most widely used grades in this GROUPThe ferritic stainless steels are identified by the Type 400 series. They cannot behardened by heat treatment. They are straight chromium alloys and only moderatelyhardened by cold working. This group is magnetic and has good ductility and resist-ance to corrosion. Type 430 (16% chromium) is the general purpose stainless STEEL ofthe ferritic GROUP This group is also identified by the Type 400 series and are hardenable by heattreatment.

5 They are magnetic and resist corrosion in mild environments. The ductility ofthis group is fair to good. Type 410 ( chromium) is the most widely used alloy ofthis Specialty STEEL Industry of North America wishes to acknowledge informationobtained from the International Nickel Company, the Southern Africa Stainless SteelDevelopment Association, the STEEL Service Center Institute and the Nickel DevelopmentInstitute (NiDI) as having contributed to this FABRICATION 6/22/01 2:57 PM Page 52 Exhibit 1 RELATIVE FABRICATION CHARACTERISTICS OF STAINLESS STEELSG roupAusteniticFerriticMartensitic201, 202,316301, 302,316L405304, 304L309S317321430442403440 AType Number305303*310S317 LMN347439446410420440 CAir HardeningNoNoNoNoNoNoNoYesYesYesBlanking FFFFFEEEEGB razing, SilverG GGGGGGGGB uffingG GGGGGGGGD rawing, DeepE GEGEFENRNRF orming, HotGFGGGGGGGGF orming, ColdGFGGGGFGFNRG rinding, Ease ofFGFFFFFGEEG rinding (magnetic)NoNoNoNoNoYesYesYesYesYesHarde nable by Heat TreatmentNoNoNoNoNoNoNoYesYesYesPunching (perforating)

6 F FFFGGGGGP olishingGGGGFGGGGGR iveting, HotGFGGGGGGNRNRR iveting, ColdGFGGGGGGNRNRS hearing, ColdFFFFFGGGGFS oldering G G GGGGGGGGB razingGGGGGGGGGGS pinningG GGGGFFNRNRW eldingENREEEFFFFFM achiningFEFFFGFGFNRCode:E = ExcellentG = GoodF = FairNR = Not generally recommended (Poor)CHARACTERISTICS OFSTAINLESS STEELS tainless steels can be fabricated bymethods similar to those used for carbonsteels and other common metals. How-ever, changes may be necessary to theextent that they differ in yield strengthand rate of work hardening. All havework hardening rates higher than com-mon carbon steels, but the austeniticsare characterized by large increases instrength and hardness with cold the exception of the resulfurized free-machining grades (Type 303 is thecommon type, but many others can betreated to be more easily machined), allstainless steels are suitable for crimpingor flattening operations.

7 The free machin-ing grades will withstand mild longitudi-nal deformation, but may exhibit sometendency to splitting. In spite of theirhigher hardness, most martensitic andall of the ferritic types can be success-fully fabricated. Exhibit 1 shows the rela-tive FABRICATION characteristics of threegroups of stainless STEEL .*Chemistry designed for improved machining (as are other grades, , 416, 420F, 430F, 440F) FABRICATION PROPERTIES OFSTAINLESS STEELE xhibit 2 lists the 30 grades and theirUNS number (the Unified NumberingSystem was developed by the AmericanSociety for Testing Materials and theSociety of Automotive Engineers for allcommercial metals and alloys).

8 Somestainless types are not suitable for certainapplications and others are designed tobe better adapted. Exhibit 2 shows thesuitability of these 30 types in variousfabrication Note: In all cutting opera-tions on stainless steels the followingguidelines are helpful in maintaining corrosion resistance: No contamination by ferrous (iron orsteel) material or particles shouldtake place. Mechanically cut edges will naturallyform the corrosion resistant passivefilm. The formation of such a passivefilm on cut edges will be enhancedby a chemical (acid) passivationtreatment with nitric acid. Thermally cut edges may be affectedin terms of chemical compositionand metallurgical structure.

9 Removalof affected surface layers by dress-ing is necessary so that impairedareas of mechanical and corrosionresistant properties are operations are usually neces-sary to obtain the desired blank shape orsize prior to forming operations and alsoto trim a part to final size. Mechanicalcutting and thermal cutting are the twomost frequently used cutting operationsand the specific methods available arediscussed in the individual sections methods are useable with stain-less STEEL , but because of the differencesin strength, toughness and rate of workhardening, certain details in the opera-tions may need to be modified relative tocarbon stainless steels have work (orstrain) hardening characteristics.

10 It is particularly notable in the 300 the drill bits contact the surface ofthe stainless STEEL and as they penetrate,the material will harden and it will bemore and more difficult to continuedrilling with the same pressure andspeed. Drilling bits are generally madefrom high speed steels and monolithiccarbide. It is important to lubricate thedrill under pressure. Soluble oils or cutting oils are often used (it is advisableto seek professional recommendationson specific oils that are available for usewith stainless STEEL ).For long products and thick sheetsand plates, the point angle should be120 to 135 degrees.