UDC 621.746.27.047 : 669.14-194.3 Continuous Casting of High Alloy Steels* By Fumio HOSHl** and Yoshimasa AOYAMA*** Synopsis (3) The number of machines excluding tes t plants The /JalJer is a technical note for the continuous castillg of higlt alloy are totall y twelve strands; nine for slab, two for b ille t steels, esllecially of tlte stainless steel. Charactpristics of steels, facilities, or bloom, and one for slab a nd billet. Of these operatiolls, defects alld their remedies, propertips ~f tlle /Jroducts, yield twelve stra nds, ten are exclusively onl y for stainless and cost of tlte products com/Jared with ingot making process are rlescribed steel and the remaining two are both for stainless and respectively based on mallY research and invesiigatioll papers. Tlte outline plain carbon steel. The sectional dimension of the of j alHUlese casters is surveyed through answers to tlte questionnaire sellt strands and the capacity of these facilities installed are to domestic stainless steel makers. smaller than those for the plain carbon steel. The I. Introduction capacity of the plants, exclusive o nl y for stainless steels, is estimated at 130000 t/month. It is evident that the continuous casting of high (4) As for machine type, the vertical tvpe ac­ alloy steels is also grounded on the same technical counts for eight a nd bending one for four, but the basis as that of plain carbon steels. About twenty m achines constructed recently a re a ll of bending type. years have passed since conLinu ous casting of steel had been industrialized. W e might say that continuous casting of steels began with high alloy steels, and it III. Characteristics of Steel would also be true to say that it has been developed through effol-Ls a nd achievements of many pioneers]) J. Characteristics of Molten Steel with some different backgrounds. W e can consider many importa nt characteristics A few years ago, we reported a technical note on o f steels in rela tion wi th continuous casting; such as the continuous casting of high alloy steels. 2 ) In the chemical co mpositions, Q, tL the extent of deoxida­ presen t pa per, adding recent resul ts, we describe tion a nd of oxidizing, casting temperature, liquid us briefly but as completely as possible the outline of a nd soli dus temperature, the degree of super-heat, j a panese casters, characteristics of steel, faci li ties a nd viscosity, fluidity, surface tension, specific heat o f the operations, defects observed on strand and final pro­ molten steel, and so on. These fac tors influence each ducts, their remedies, properties of products, yield a nd other in complicated manner, so we cannot isolate its influence on cost, based specificall y on continuous each influence clearly. However, some concrete casting of stainless steel. examples are given below. It is well known that Cr is a n element to decrease II. Outline of Japanese Casters the activity of oxygen greatl y. For example, activity W e hope that japan would be one of the most coefficient of oxygen fo in SUS 430 is nearly equal to 4 advanced countries in the fie ld of continuous casting 1/8 of that in plain carbon steel. ) Normall y, stainless of high alloy steels in terms of the number of plants, steels contain a substantial amount of Mn and Si a nd the amount of products and the technique on opera­ sometimes we use Al a nd Ti as a d eoxidizer, so the tion. Now, in j apan the ratio of continuously cast melt does not necessari ly contain eight times of stainless steels to the total stainless steels has risen to oxygen compared with tha I of plain carbon steel under over 60% ,3) a nd the continuous casting process has the same carbon a nd temperature conditions. Thus, become a main casting method in the steelmaking of the residual prima ry a nd secondary deoxidation pro­ stainless steel. An outline of the continuous casting ducts through rapid solid ification in the continuous of high a ll oy steels in j apan is shown in Table 1 ( p. p. casting tend to affect the quality of cast products more 430 - 3), based on the a nswers to ques tionnaires sent markedly than in the case of ingot making or of plain to domes tic mills. The main features may be sum­ carbon steels. The chemical composition of steel and m ari zed as follows. the method of deoxidation affect the shape and the (1) The continuous casting is operated in almost a mount of nonmetallic inclusions. Examples are a ll the main stainless steel makers in j apan . shown in Figs . 15 ) and 26 ) (see p.432). All elements, (2) Almos t all the cast steels a re stainless steels. such as Cr, Mn, Si, AI a nd Ti, are oxidized mort' Also almost all the steel grades corres ponding to easily than Fe, so that preventing the ox id a tion o f " SUS" of j a pan Industrial Sta ndards have been molten steel during casting is of most importance. covered. The fluidity of molten steels also appears to be one * Pa rtl y published in T elsu-/o-Hagane, 60 ( 1974), 82 1, in J a panese. Presented a t the 40th and 4 1st Nishi yama M emori al Technical Lectures, ISIJ, September, 1976, in Tokyo and October, 1976, in Kitakyushu. M anuscri pt received J uly 4, 1977. ** Steelmaking and Hot R olling Department, Shunan ''''orks, Nisshin Steel Co., Ltd., Shin-Nanyo, Yamaguchi 746. *** Nisshin Steel Co., Ltd., M arunouchi, Chiyoda-ku, Tokyo 100. Technical Features ( 429 ) ( 430 ) Tran sactions ISH, Vol. 18, 197 8 Table I. Continuous casting of high alloy steels in Japan Nippon Steel Corp. Pacific Metals Nippon Yakin Hikari I Murora n· Hachinohe Kawasaki ' EF-AOD Process EF-AOD LD-RH·OB EF-AOD.VD ELO-VAC 1------------ ------------------------ ----------- EF x 2 Steelmaking EF x 2 LD x2 AOD x l EF x 3 I Furnace & numbe r process & unit I VD x l AOD x l RH x l (ASEA-SKF) VOD x l Capacity; F'ce/ Ladle (t) 50, fIl /- fIl/50 30/ 30 fIl / 65, 30 '40 Start·up date Dec. 19f1l Oct. 1968 J uly 1965 Feb. 1964 Ma r. 1965 Dec. 1970 Number of machine 2 (Billet) or Number of strand 1 (Slab) I (Billet) 1 (Slab) 1 (Slab) I (Slab) 1 (Slab) Machine type Ver tica l Vertica l Height or R/ Le ngth (m) 11. 4/ 23. 4 16.0/ 27. 0 1--v-ll-e~-5~'-~C-I~-~-+--~-:-~~-'/-:a-2 1--II--~-:-ro-t ~_:0_a. _15__ I---~-:-.~-~-i:-:-15--1 Designe'l" Concast Concast Hitachi DEMAG Concast Concast Outline of --______1------------'------ 1 continu ous Manufacturer Sumitomo S. M. t' Hi tachi DEMAG Sumitomo S. M. casting unit I Straight Straight-- -----s;r" ~I- St rai ~ 1 Straight Stra ight Mold type - Block or tube Width adjustable 125 115 x 1l5 Thickness I 130, 140 210 x 210 150,220 150 130 x 130 145 145 Dimension of ,------I cast product 1 Width 1 700~1,350 210 x 250 730-1.300 ~~~ 1 : ~~ ~ :~~ 950~1,300 1 (mm) :-------1------- 1-------------1 1--s-e-c-o-n d-a-r-y-.-L-e-~-1 :-lt-' I:-t-~,-ll-) -1-4-,-5_00_:_. -: '-0-o-0-1-2-, -80-0-~-:-' 0_0_0_, ~oo~:' 400 II M a~~.: 800 I 4, OOO~:' 500 I 4'000~:' 500 cooli ng zone Me thod - - - \-V ater s pray Water s pray \V ater spray Cutting method I Powder cutling Powder cu tting Powder cu tting Powder cutting Powder cutting I Powder cutting (Propane) ___!. ~~~)P~ _ ( P r opa~ 1. _ (Propane) I (- ) (- ) Specification withdrawa l speed . 5 1--0 2~0 . O. 2~2. 0 0 ,__ _ O. 2~ 1.4 (m/ mln) O~I ~5. --- -'---1-- - I Standard cas ting spee d (m/ min) 0.8 ~ 1.1 o. 5~0. 9 ~W I~t ~: 8:::J ~ Capacity of --- Slab continuous Capacity (t I (hr/ stra nd)) 25~30 1 1_0 ~_30__ ! ___ 4_ 5 _~_72_ _ _ B_i l_I e_t_I _2~_15____ _ casting I Planed or sta nda rd ca pa ~ 0-;- 1---10 4, 500 1 15,000 I 7,500 33,000 (t month) , _--, I---M- a-x-. -ac-t-u-a l capac ity 1--- -, 9~ (t 'month) 12 ~ , 900 15, fIlO 3,725 21,000 ---------1 ----------------------1 Ratio of continuous casting stee l (°0) 70 20 40 I Stainl~s steel I Stainless steel 95 I f s-te-e-I Staini'li>s steel I----S-ta- i-n-Ie-s-s- s-t-ee- I- IO-O--- Ratio of high alloy steel (fa) Sta inl ess stee l Stainless steel Stai nl 2~s I 10_0__ 1 100 __ SUS 20 1, 202 ,SUS ~02, 304 IS US 304 SUS ~~~: ~~~ SUS 301, 302 30 I, 302 305, 308 410, 430 308, 309 304, 304 L Authori ze d standard g rade 304, 305 316 310, 316 309, 316L (SUS, AISl, etc.) 316, 32 1 410, 430 m' 32 1 32 1, 347 410, 430 410, 420 430 - YUS 120 1 Nothing NAS 45M (I6Cr, 9Mn, 2Ni) (24Cr, 5Ni, 1.5Mo) 1- I YUS 27 A NAS 126 (I7C,', 6N i. 2Cu) (l8Cr, 12N i, 3.5Si) Casting grade of h igh a ll oy steels Other standard grade Te chnical Features Transactions ISIJ, Vol. 18, 1978 ( 431 ) (This table is a summa ry of a nswers to questionna ires se nt for stainless steel makers in J apan) Sumitomo Nippon Metal Industry Kawasaki Steel Corp.