CN-122029301-A - Cold-rolled steel sheet and method for producing same

Abstract

A cold-rolled steel sheet containing carbon in a high content of 0.80 to 1.25 mass% is provided with excellent machinability and punching workability. A cold-rolled steel sheet having a predetermined composition, wherein cementite particles having an area of 0.06 [ mu ] m 2 or more have an average particle diameter of 0.65 [ mu ] m or less, wherein the average particle diameter is 2.0 mass% or more, wherein the number density of pores having an area of 0.01 [ mu ] m 2 or more is 50000/mm 2 or more, and wherein the Vickers hardness is 200HV or more and 400HV or less.

Inventors

• YAMASAKI KAZUHIKO
• MATSUDA TAKASHI
• Kiko Akiya
• Itai Yasumasa
• TSUCHIYA KOJI
• MATSUMURA YUTA
• HIRUTA SHUHEI
• 11

Assignees

• 杰富意钢铁株式会社
• 株式会社特殊金属超越

Dates

Publication Date

20260512

Application Date

20241008

Priority Date

20231106

Claims (3)

1. 1. A cold-rolled steel sheet having a composition containing, in mass%: C:0.80~1.25%、 Si:0.10~1.0%、 Mn:0.20~3.0%、 P:0.001~0.05%、 s is less than 0.03%, Al:0.001~0.1%、 N:0.001~0.01%、 0.0100% Or less of O, 0.56-2.0% Of Cr At least 1 selected from the group consisting of Nb 0.029-0.24%, ti 0.01-0.21% and V0.01-0.21%, The balance of the composition of the components being Fe and unavoidable impurities, and The total content of Nb, ti and V is 0.24 mass% or less, Cementite particles having an area of 0.06 [ mu ] m 2 or more have an average particle diameter of 0.65 [ mu ] m or less, and an A value defined by the following formula (1) is 2.0 mass% or more, The number density of pores having an area of 0.01 μm 2 or more is 50000/mm 2 or more, The cold-rolled steel sheet has a Vickers hardness of 200HV or more and 400HV or less, A=(3/7)C Mn +C Cr ...(1) Wherein C Mn in the above formula (1) is the Mn content (mass%) in the cementite particles having an area of 0.06 μm 2 or more, and C Cr is the Cr content (mass%) in the cementite particles having an area of 0.06 μm 2 or more.
2. 2. The cold-rolled steel sheet according to claim 1, wherein the composition of the components further contains, in mass%, a component selected from the group consisting of: ta is 0.10% or less, W is less than 0.10%, B is less than 0.0100%, Mo is less than 1.00%, 1.00% Or less of Co, Ni less than 1.00%, Cu is less than 1.00%, 0.200% Or less of Sn, 0.200% Or less of Sb, Ca is less than 0.0100%, 0.0100% Or less of Mg, REM is less than 0.0100%, Zr of less than 0.100%, Te is less than 0.100%, Hf 0.10% or less Bi of 0.200% or less At least 1 of the group consisting of.
3. 3. A method for manufacturing a cold-rolled steel sheet, comprising: a steel slab having the composition according to claim 1 or 2 is heated at a slab heating temperature of 1100 ℃ or higher and a slab heating time of 60 minutes or higher, The heated steel slab is hot rolled at a finishing temperature of higher than Tc defined in the following (2) to produce a hot rolled steel sheet, Cooling the hot-rolled steel sheet at an average cooling rate of 20 ℃ or higher per second and a cooling stop temperature of Tc or lower, Coiling the cooled hot rolled steel sheet at a coiling temperature of 530 ℃ to Tc, The 1 st annealing is performed for the coiled hot rolled steel sheet for more than 1 time under the conditions that the annealing temperature is more than 600 ℃ and less than Tc and the annealing time is more than 3 hours, The hot-rolled steel sheet after annealing of the 1 st step is subjected to a2 nd annealing for a period of 3 hours or more in which the rolling reduction is 15% or more and the annealing temperature is 600 ℃ or more and Tc or less, and then subjected to a final cold rolling in which the rolling reduction is 20% or more and 80% or less, Tc(°C)=723-10.7×Mn-16.9×Ni+29.1×Si+16.9×Cr+6.38×W...(2) The symbol of the element in the above formula (2) represents the content (mass%) of each element, and is set to zero when the element is not contained.

Description

Cold-rolled steel sheet and method for producing same Technical Field The present invention relates to a cold-rolled steel sheet, and more particularly, to a cold-rolled steel sheet excellent in machinability and punching workability and a method for manufacturing the same. Background Cold-rolled steel sheets are widely used as materials for manufacturing various steel parts. Among them, cold-rolled steel sheets formed from high-carbon steel have high hardness by quenching after being formed into steel parts, and are therefore used in applications requiring wear resistance, such as parts for textile machines, bearing parts, and machine and household tools. On the other hand, in the case of forming steel parts such as textile machine parts, bearing parts, machine and household tools before quenching, cutting processing by a metalworking saw, a face milling cutter, an end milling cutter and the like is performed. If the cold-rolled steel sheet as a material has poor machinability, the wear of the cutting tool rapidly occurs, and the frequency of replacement of the cutting tool increases, which is also disadvantageous in terms of productivity and cost. Therefore, the cold-rolled steel sheet is required to have excellent machinability. In addition, in steel members such as knitting needles, which are members for textile machines, prior to cutting, blanking die cutting is performed on the outer shape by punching. Therefore, the cold-rolled steel sheet is required to have excellent blanking workability, that is, to be less likely to cause burrs and sagging of the blanking end face. Accordingly, various techniques for improving machinability and punching workability have been proposed. For example, patent document 1 proposes a technique for improving machinability of steel by controlling the number and average particle diameter of carbide in a spheroidized structure in steel containing 0.70 to 1.10 mass% of C. Patent document 2 proposes a technique for improving machinability of steel by controlling an average value of C content in a region from an outer periphery to a depth of 200 μm to a specific range in a steel wire rod having 0.75 to 1.2 mass% of C. Patent documents 3 and 4 propose techniques for improving punching workability by controlling the ratio of the number of carbides at ferrite grain boundaries to the number of carbides in ferrite grains within a specific range in a steel sheet containing 0.30 to 1.30 mass%. Patent document 5 proposes a technique for improving punching workability by introducing 100 or more pores per 1mm 2 into a steel structure in a steel sheet containing 0.70 to 0.95 mass% of C. Prior art literature Patent literature Patent document 1 Japanese patent laid-open publication No. 2005-307320 Patent document 2 Japanese patent laid-open No. 2001-049388 Patent document 3 Japanese patent laid-open No. 2008-303415 Patent document 4 Japanese patent application laid-open No. 2009-215612 Patent document 5 Japanese patent application laid-open No. 2011-012316 Disclosure of Invention Problems to be solved by the invention However, these prior arts have the following problems. For example, in the technique proposed in patent document 1, the machinability of steel is improved by limiting the number of carbides. However, since the steel is soft, the steel is greatly subject to sagging during blanking. In addition, in the technique proposed in patent document 2, the machinability is improved by reducing the C content of 200 μm in the surface layer by decarburization. However, in applications such as knitting needles, a thin cold-rolled steel sheet having a thickness of about 0.4mm is used, and the technique of patent document 2 cannot be applied to such a thin cold-rolled steel sheet. This is because the technique of patent document 2 reduces the C content almost throughout the thickness and the strength is insufficient. Further, since the steel of patent document 2 is also soft, the steel is greatly subject to sagging during punching. In the techniques proposed in patent documents 3 and 4, punching workability is improved by making the number of carbides in ferrite grains larger than the number of carbides in ferrite grain boundaries. However, even in the steel sheet obtained by this method, the soft steel sheet is greatly subject to sagging during blanking. On the other hand, in the case of a hard steel sheet, the machinability is insufficient. In addition, in the technique proposed in patent document 5, burrs generated during blanking can be reduced by introducing a void into the steel structure. However, since the steel sheet is soft, the steel sheet is greatly subject to edge collapse during punching. In addition, the machinability is also insufficient. As described above, in practice, it is still impossible to achieve both machinability and punching workability at a high level. The present invention has been made in view of the above-described circumstances, and an object of the present inven