Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper

Definitions

• a steel having excellent rust resistance comprising 0.001 to 0.15% of carbon, 0.01 to 1.0% of silicon, 0.01 to 1.0% of manganese, 0.01 to 0.5% of copper, 0.003 to 0.3% of sulfur and titanium in an amount enough to attain a Ti/S ratio of 2 or more, with the balance being iron and unavoidable impurities.
• the present invention relates to steel sheet having excellent rust resistance, useful as materials for automobile and can-making.
• the present inventors have made extensive studies for clarifying the causes of rust formation, and have discovered that the rust formation is attributed directly to the fact that u(Mn-Fe)S contained in the steel is dissolved into dews formed on the steel surface. Namely it has been found that this m(Mn-Fe)S changes its conditions under both of an oxidizing atmosphere and a reducing atmosphere and causes the rust formation. Therefore, it is necessary to make the sulfur content in the steel as low as possible so as to lower the a(MI1'F6)S content in the steel in order to prevent or suppress the rust formation. However, it requires high cost to reduce the sulfur content in the steel, and yet it is impossible to completely remove the sulfur content. Therefore, other methods must be relied upon to reduce or prevent the formation of the Based on the above discoveries, the present inventors have developed steel sheets having excellent rust resistance by fixing the sulfur content as sulfide unsolubles into the dews.
• One of the objects of the present invention is to provide a steel comprising 0.001 to 0.15%, preferably 0.005 to 0.05% of carbon, 0.01 to 1.0%, preferably 0.01 to 0.1% of silicon, 0.01 to 1.0%, preferably 0.1 to 0.3% of manganese, 0.01 to 0.5%, preferably 0.02 to 0.25% of copper, 0.003 to 0.03%, preferably 0.003 to 0.02% of sulfur, titanium in an amount enough to obtain a Ti/S ratio of more than 2, thus preferably 0.01 to 1.0% of titanium, optionally 0.1 to 1.0% of chromium and/or 0.001 to 0.05% of boron, with the balance being iron and unavoidable impurities.
• the present invention has, as its object, to provide a steel sheet having excellent rust resistance under an indoor condition such as high moisture as in the summer season in Japan.
• the basic elements composing the steel of the present invention are silicon, manganese copper, titanium and sulfur other than iron and carbon, and these elements are classified as the first group elements.
• the second group elements are chromium and/ or boron.
• titanium in combination with copper contributes to improvements in the rust resistance, and remarkable rust resistance improvement is given when the ratio of T i/ S is 2 or more.
• the second group elements primarily tend to improve the rust resistance, and the rust resistance may be further improved by the presence of the first and second group elements.
• the basic steel composition of the present invention comprises 0.001 to 0.15% of carbon, 0.01 to 1.0% of silicon, 0.01 to 1.0% of manganese, 0.01 to 0.5 copper, 0.003 to 0.03% of sulfur and titanium in an amount enough to have a Ti/S ratio of 2 or more, and a modified steel composition of the present invention comprises one or more of the second group elements in an amount of 0.1 to 1.0% for chromium and 0.001 to 0.05% for boron.
• the carbon content is necessary to give the desired strength, but more than 0.15 of carbon lowers the elongation of the steel and deteriorates the rust resistance. While less than 0.001% of carbon lowers the strength and requires a longer refining time, thus causing adverse effects on economics and productivity.
• Silicon and manganese are necessary as deoxidizing elements in the steel making in an amount of not less than 0.01%, but excessive addition of these elements causes embrittlement of the steel and excessive strength. Thus the upper limits of these elements are limited to 1.0%.
• Copper when present with other elements, is effective to improve the rust resistance, but its effect is recognized when contained less than 0.01%, While more than 0.50% of copper causes embrittlement of the steel and deteriorates the workability.
• the sulfur content is limited to a range of 0.005- 003%.
• the titanium content is defined so that the ratio of Ti/S is not less than 2.
• titanium is as follows: if the other sulfide former elements than titanium are not contained in the steel, the amount of titanium necessary for fixing all the sulfur in the steel is stoichiometrically 48/32 times more than the amount of sulfur. Since the commercial steel contains, however, manganese which is a typical sulfide former element. The above-mentioned amount of titanium are not enough for fixing all the sulfur in the steel as titanium sulfide and a part of the sulfide in the steel remains as manganese sulfide which causes rust formation.
• chromium as an optional element is that when it is contained in an amount of 0.1% or more its effect on promoting the rust resistance is remarkable, but more than 1.0% of chromium brings only 'high production cost.
• Boron is limited to 0.001 to 0.05% for the reason that less than 0.001% of boron show no substantial effect and more than 0.05% of boron causes embrittlement of the steel.
• the above steel compositions may be produced by TABLE 1 Indoor Moisture testing exposure Hot Gold Gold Chemleal composition (percent) rolled, rolled, rolled, annealed annealed annealed C Si Mn T1 S Cu Cr B sheet sheet sheet Conventional steels What is claimed is: 1. A steel having excellent rust resistance consisting melting in an ordinary steel making furnace, such as an electric furnace and a converter in combination use of vacuum degassing, if necessary, then making slabs by continuous casting or ordinary ingot making method, hot rolling, cold rolling and annealing. In some cases, the steel sheet as hot rolled, or as hot rolled and normarized or annealed, or steel sheet as cold rolled may be used for the final product.
• Table 1 shows results of rust formation tests made on the present invention steels and convention steels both obtained by melting in a converter, ingot-making, hot rolling and annealing, and on the inventive steels and conventional steels both obtained by hot rolling, and then cold rolling and annealing.
• (A) in Table 1 means that test pieces of 3 mm. thickness, 30 mm. width and 50 mm. length and butf polished essentially of 0.001 to 0.15% of carbon, 0.01 to 1.0% of silicon, 0.01 to 1.0% of manganese, 0.01 to 0.5% of copper, 0.003% of sulfur and titanium in an amount enough to attain a Ti/S ratio of 2 or more, with the balance benig iron and unavoidable impurities.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Sheet Steel (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=14195936

Family Applications (1)

Country Status (2)

Cited By (1)

• 1971
  • 1971-12-04 JP JP46097572A patent/JPS4861316A/ja active Pending
• 1972
  • 1972-11-30 US US00310846A patent/US3832166A/en not_active Expired - Lifetime

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