Abstract: Method for manufacturing a tapered rod for a coil spring from a metallic material of mainly steel in a linear state, by imparting heating to the same with a predetermined temperature gradient pattern in the axial direction thereof while or before pulling by tensile force the metallic material chucked at two axially distant points in either direction in a gradually decreasing or stepwise decreasing speed, until a desired tapered portion is formed.

Abstract: Mechanical anisotropy of a free cutting steel having excellent machinability can be effectively decreased by controlling inclusions so that the steel may contain inclusion A which softens at a temperature below 1000.degree. C. and inclusion B which has a melting point above 1300.degree. C. but exhibits plasticity at a temperature between 900.degree. and 1300.degree. C., that the inclusion A and the inclusion B may exist in a mutually adhered form, and that the areal percentage of the inclusion A may be at least 1% of areal percentage of the inclusion B.Typical compositions of the inclusion A are: Pb, Bi, MnS--MnTe, SiO.sub.2 --K.sub.2 O, SiO.sub.2 --Na.sub.2 O, SiO.sub.2 --K.sub.2 O--Al.sub.2 O.sub.3, SiO.sub.2 --Na.sub.2 O--Al.sub.2 O.sub.3 and SiO.sub.2 --Na.sub.2 O--CaO--MnO; and typical compositions of the inclusion B are: MnS, MnSe and Mn(S,Se).

Abstract: A steel for cold forging containing C up to 0.6%, Si up to 0.5%, Mn up to 2.0%, S 0.003 to 0.04% and Te up to 0.03%, wherein ratio %Te/%S being at least 0.04, and further, Al up to 0.04%, N up to 0.02% and O up to 0.0030%, and the balance being substantially Fe exhibits both good formability in cold forging and good machinability.The steel may further contain one or more of additional alloying elements selected from the group of Ni, Cr and Mo, the group of V, Nb, Ti, B and Zr, and the group of Pb, Se, Bi and Ca.The steel for cold forging having good machinability is made preferably by agitating molten steel containing adjusted amounts of the alloying elements other than Te, and, if used, members of the Pb group, by introducing non-oxidizing gas thereinto so as to float up and separate large sized particles of non-metallic inclusions, and subsequently adding predetermined amount of Te and other elements.

Abstract: A free cutting steel for machine structural use containing C up to 0.6%, Si up to 2.0%, Mn up to 2.0%, S 0.04 to 0.4%, Te 0.002 to 0.5% and O 0.0010 0.0300%, the balance being substantially Fe exhibits excellent machinability when the MnS-based inclusion is in the form of particles of 5 to 100.mu. long, 1 to 10.mu. wide, wherein the aspect ratio length/width is not larger than 10, and at the density of 20 to 200 particles per 1 mm.sup.2 of the matrix cross section.A free cutting steel for machine structural use containing C up to 0.6%, Si up to 2.0%, Mn up to 2.0%, S 0.04 to 0.4% and Te up to 0.1%, wherein %Te/%S is at least 0.04, O up to 0.003% and N up to 0.0200%, the balance being substantially Fe exhibits improved rolling-contact fatique strength when at least 80% of sulfide-based inclusion particles of 10.mu. long or more have the aspect ratio length/width of 5 or less, and when areal percentage of alumina cluster in the matrix cross section is not higher than 0.5%.

Abstract: Machinable ferrite stainless steels having an excellent corrosion resistance, consisting of not more than 0.030% of C, not more than 0.050% of N, not more than 0.012% of O, not more than 0.8% of Si, not more than 1.6% of Mn, 0.05-0.40% of S, 16-22% of Cr, and 1-3% of Mo, or at least one of 0.03-0.25% of Pb, 0.03-0.20% of Se and 0.01-0.15% of Te, the remainder being Fe, provided that the sum of C and N is not more than 0.060% and Mn/S is 2-5, characterized by that Cr content based on 100 parts by weight of sulfide inclusions formed in the said steels is 10-50 parts by weight.This is a divisional application of application Ser. No. 942,138, filed Sept. 13, 1978.

Abstract: Machinable ferrite stainless steels having an excellent corrosion resistance, consisting of not more than 0.030% of C, not more than 0.050% of N, not more than 0.012% of O, not more than 0.8% of Si, not more than 1.6% of Mn, 0.05-0.40% of S, 16-22% of Cr, and 1-3% of Mo, or at least one of 0.03-0.25% of Pb, 0.03-0.20% of Se and 0.01-0.15% of Te, the remainder being Fe, provided that the sum of C and N is not more than 0.060% and Mn/S is 2-5, characterized by that Cr content based on 100 parts by weight of sulfide inclusions formed in the said steels is 10-50 parts by weight.