30 results about "Free machining steel" patented technology

Free machining steel for use in machine structures capable of stably and reliably providing excellent machinability (chip disposability and tool life) and mechanical characteristics (transverse direction toughness) comparable, in a Pb free state, with existent Pb-added steels the machining steel being manufactured so as to contain 0.0005 to 0.02 mass % of Mg and provide a distribution index F1 for the sulfide particles defined by the following equation (1) of 0.4 to 0.65 or a distribution index for the sulfide particles defined by the following equation (2) of 1 to 2.5:as described in the specification.

The present invention provides a low-carbon resulfurized free machining steel product excellent in machinability typified by finished surface roughness even though toxic Pb or special elements such as Bi or Te are not added, and a suitable production method thereof. A steel product has a specific composition, has contents of Mn and S satisfying the following conditions: 0.40≦Mn*S≦1.2 and Mn / S≧3.0, and contains a ferrite-pearlite structure as the metallographic structure, in which the average width (μm) of sulfide inclusions in the steel product is 2.8*(log d) or more, wherein d (mm) is the diameter of the steel product, and pro-eutectoid ferrite in the metallographic structure has a hardness HV of 133 to 150 or a difference in deformation resistance at a strain of 0.3 between 200° C. and 25° C. is 110 MPa or more and 200 MPa or less, the deformation resistances being determined in a compression test at a deformation rate of 0.3 mm / min.

Disclosed is a free machining steel for machine structural use, which can realize very good chip disposability without incorporation of any harmful material such as lead (Pb). This free machining steel is a hot rolled or hot forged free machining steel having improved chip disposability. The free machining steel comprises, by mass, carbon (C): 0.01 to 0.70%, silicon (Si): 0.05 to 2.00%, manganese (Mn): 0.20 to 3.50%, calcium (Ca): 0.0003 to 0.01%, sulfur (S): 0.020 to 0.300%, aluminum (Al): 0.002 to 0.300%, nitrogen (N): 0.003 to 0.035%, and oxygen (O): 0.0010 to 0.0080% with the balance consisting of iron (Fe) and unavoidable impurities. The steel comprises sulfides having the major axis of from 0.5 mum to 20 mum, exclusive, and comprising MnS as the main component, in a number of not less than 30% of the total number of sulfides. The steel also comprises oxide inclusions having the major axis of from 0.5 mum to 50 mum, exclusive, and being present either together with sulfides or singly, in a number of not less than 10 per mm<2>of the inspection area.

The invention belongs to the field of metallurgy and relates to rolling process of lead-containing free-machining steel. A rolling mill is used for rolling, in the rough rolling process, the rolling temperature is controlled at 1030-1060 DEG C, the former three-pass material form is reduced 1-3mm based on the standard material form; in the intermediate rolling process, the roll material form is the standard material form, and the rolling temperature is controlled at 980-1030 DEG C; in the pre-finish rolling process, the roll material form is the standard material form, the rolling temperatureis controlled at 1060-1030 DEG C, and the temperature of the rolled piece reaches 1005-1040 DEG C after the pre-finish rolling process; in the finish rolling process, the temperature of the rolled piece in a finishing mill is less than 980 DEG C, the roll material form is the standard material form, and the rolling temperature is controlled at 1020-1050 DEG C. The rolling process can prevent steel heaping caused by the cleavage crack of the cold, hot and frailty susceptible head of the rolled piece, prevent sliding accident caused by the high temperature of the steel, steadily increase the yield of the lead-containing free-machining steel, obviously reduce the waste, and greatly reduce the 100t steel fault time.

The present invention provides a low-carbon resulfurized free machining steel product excellent in machinability typified by finished surface roughness even though toxic Pb or special elements such as Bi or Te are not added, and a suitable production method thereof. A steel product has a specific composition, has contents of Mn and S satisfying the following conditions: 0.40 Mn*S 1.2 and Mn / S 3.0, and contains a ferrite-pearlite structure as the metallographic structure, in which the average width ( m) of sulfide inclusions in the steel product is 2.8* (log d) or more, wherein d (mm) is the diameter of the steel product, and pro-eutectoid ferrite in the metallographic structure has a hardness HV of 133 to 150 or a difference in deformation resistance at a strain of 0.3 between 200 DEG C and 25 DEG C is 110 MPa or more and 200 MPa or less, the deformation resistances being determined in a compression test at a deformation rate of 0.3 mm / min.

The invention discloses a bismuth-titanium alloy, and belongs to the technical field of the preparation of free-machining alloy steel. The bismuth-titanium alloy comprises the following components in percentage by weight: 15 to 75 weight percent of bismuth, less than or equal to 0.8 weight percent of inevitable impurities, and the balance of titanium. The invention has the characteristics that the alloying treatment is feasible, the yield of the bismuth is high and the like; and the bismuth-titanium alloy is applicable to additives of alloying treatment of free-machining steel.

Provided is a lead-containing free-machining steel having excellent machinability. This lead-containing free-machining steel contains, in terms of mass%, 0.005-0.2% C, 0.3-2.0% Mn, 0.005-0.2% P, 0.01-0.7% S, 0.03-0.5% Pb, 0.004-0.02% N, and 0.003-0.03% O, with the remainder comprising Fe and impurities. The steel contains Pb inclusions (40) having a diameter of 0.01-0.5 μm in terms of equivalent-circle diameter, the number of the inclusions being 10,000 per mm2 or larger.

The invention relates to a method for producing graphitized free-machining steel from intermediate-carbon manganese-silicon steel, intermediate-carbon manganese-silicon-aluminum steel and the like. The method comprises the following steps: heating casting blanks; maintaining the temperature; cooling to 1050-1150 DEG C; roughly rolling: controlling the reduction percentage of each gate to be 20-40%; cooling to 850-1000 DEG C; carrying out precision rolling according to 4-6 gates; cooling in air; quickly cooling in water to room temperature; heating the precision rolling plate and maintaining the temperature; and cooling in air or cooling in a furnace to room temperature. By controlling the state of C atoms in steel and C content of austenite before tempering based on a process route of low-temperature rolling, relaxation and phase change, quenching and graphitization tempering, the invention converts all C atoms in the steel into graphite in a short time (5h). In the graphitized free-machining steel produced by the method, graphite grains in the organization are small in size and are uniform in distribution.

The invention discloses a homogeneous easy-cutting steel and a method for producing the same. The homogeneous easy-cutting steel comprises the following compositions (in percentage by weight): less than or equal to 0.12 percent of C, less than or equal to 0.07 percent of Si, 0.803 to 1.31 percent of Mn, less than or equal to 0.07 percent of P, 0.23 to 0.37 percent of S, less than or equal to 0.001percent of Al and the balance being Fe and residual elements. The homogeneous easy-cutting steel has the advantages of heat processing, good cutting performance, etc. In the homogeneous easy-cuttingsteel produced by adopting the method, elements are uniformly distributed; sulfide impurities are uniformly distributed in a cambiform or an elongated cambiform, thereby removing adverse influence oftheheat processing of FeS impurities and obviously improving the heat processing and easy-cutting performances of the produced homogeneous easy-cutting steel; and the part surface after being cut hasbet ter smoothness.

A lead-free free-cutting steel includes, by wt%, about 0.03-0.13% of carbon (C), about 0.1% or less of silicon (Si), about 0.7-2.0% of manganese (Mn), about 0.05-0.15% of phosphorous (P), about 0.2-0.5% of sulfur (S) of, about 0.001-0.01% of boron (B), about 0.1-0.5% of chromium (Cr), about 0.003-0.2% of titanium (Ti), about 0.005-0.015% of nitrogen (N), about 0.03% or less of oxygen (O), residual iron (Fe), and other unavoidable impurities. In the lead-free free-cutting steel, the number of manganese sulfide (MnS) inclusions having a particle size of about 5 µm 2 or more may include in the range of about 300-1000 per mm 2 of a material in a section of a wire rod rolling direction. The present invention is also related to a method of manufacturing an eco-friendly lead-free free-cutting steel by properly controlling a total oxygen content by step in steelmaking steps.

The invention discloses a high-intensity non-quenching and tempering easy-cutting steel used for a vehicle connection rod and a technical method thereof. The invention starts from the principle of improving the intensity of the non-quenching and tempering easy-cutting steel and leads the anti-tension intensity of the non-quenching and tempering easy-cutting steel containing 0.30 to 0.40 percent of carbon to be 1000MPa and the yield strength to be 750MPa by adjusting the components. The technical scheme of the invention is: the high-intensity non-quenching and tempering easy-cutting steel used for a vehicle connection rod consists of the elements of C, Si, Mn, Al, P, S, Cr, V, N and Fe; the weight percentages of the component elements are: 0.30 to 0.4 percent of C, 0. 50 to 0.70 percent of Si, 0.80 to 1.20 percent of Mn, equal to or less than 0.040 percent of P, 0.030 to 0.060 percent of S, 0.010 to 0.040 percent of Al, 0.10 to 0.40 percent of Cr, 0.10 to 0.30 percent of V, 010 to 0.015 percent of N and the rest is Fe and unavoidable impurities. The heating temperature of a continuous casting blank is 1200 DEG C; the heating time is 160min; the start rolling temperature is 1100 DEGC; the final rolling temperature is 900 DEG C; the pressing volume is 16; the cooling speed after rolling is 40 DEG C / min; after bundling, the components are thrown in a pit and slowly cooled.

A low-carbon resulfurized free-machining steel is excellent in machinability and contains 0.02% to 0.15% by mass of C; 0.004% by mass or less (exclusive of 0%) of Si; 0.6% to 3% by mass of Mn; 0.02% to 0.2% by mass of P; 0.35% to 1% by mass of S; 0.005% by mass or less (exclusive of 0% by mass) of Al; 0.008% to 0.03% by mass of 0; and 0.007% to 0.03% by mass of N, with the remainder being iron and inevitable impurities, in which the ratio [Mn] / [S] of the manganese content [Mn] to the sulfur content [S] is within the range of 3 to 4, and the carbon content [C], the manganese content [Mn] and the nitrogen content [N] satisfy the following Expression (1): 10[C]×[Mn]−0.94+1226 [N]2≦1.2, wherein [C], [Mn] and [N] represent the contents on the percent by mass basis of carbon, manganese, and nitrogen, respectively.

The present invention relates to a tin-contained free machining steel. Said steel can be used for making important standard parts of high-strength Bolts, etc. of automobile and machinery, and is characterized by that in said steel 0.03-0.05% of Sn is contained. Said invention adopts the several measures of neutral covering slag molten steel, diffusing deoxygenation and solid electrolyte oxygen concentration difference cell to quickly define oxygen to develop out the leadless free machining steel (Y20Sn) with excellent mechanical propery and free-cutting machinability. The tests show that the tensile strength of its sample is up to 460MPa, percentage elongation is 25%-30% and reduction of cross-sectional area is 55%-60%.