CS232179B1 - A method of heat treating sheet metal from a structural weldable low carbon steel - Google Patents

Abstract

The invention relates to the method of heat treatment of sheets i: structural weldable low-carbon microalloyed steel or products thereof. It solves the problem of increasing the strength properties of sheets and their products after hot rolling on the basis of low-temperature annealing while maintaining the same level of toughness. The essence of the invention consists in the fact that sheet metal or products thereof in the thickness range of 3 to 25 mm are annealed at a temperature of 650 to 750 °C for a period corresponding to 1.0 to 1.5 minutes per one millimeter of sheet metal thickness. Annealing is preferably done in a continuous annealing furnace

Description

The invention relates to a method of heat treatment of sheets and products made of structural weldable low-carbon microalloyed steel in the hot-rolled state, or products made thereof with a chemical mass composition of up to 0.14% carbon, up to 0.9% silicon, 0.002 to 0.035% sulfur, 0.005 to 0.04% phosphorus, 0.05 to 0.2 zirconium, 0.8 to 4.0% manganese and optionally up to 0.30% aluminum, up to 0.6% copper, 0.05 to 0.9% molybdenum, up to 1.0% chromium and up to 4.0% nickel individually, or in their mutual combination up to 6.0% by mass, respectively. It contains 0.005 to 0.45% by weight of niobium, titanium, vanadium, boron, cerium and lanthanum and solves the problem of increasing their strength properties,

It is currently known that heat treatment of ferritic-pearlitic steels with a carbon content of over 0.14% increases their strength properties and evens out their structure if they are heat treated at temperatures of 880 to 950°C. However, in the case of sheets made of microalloyed steel with a reduced proportion of pearlite and a carbon content of up to a maximum of 0.14%, the above-mentioned heat treatment reduces their strength values, which means their deterioration, because structures made of them would require more weight. Therefore, they are used in the as-rolled or after subsequent refinement state.

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The above-mentioned shortcomings are eliminated and the problem is solved by the method of heat treatment of structural weldable low-carbon microalloyed sheets or products thereof, of the above-mentioned composition according to the invention. The essence of the invention lies in the fact that sheets or products of sheets after hot rolling, in the range of thicknesses from 3 to 25 mm, are annealed at a temperature of 650 to 750° C for a period corresponding to 1.0 to 1.5 minutes per millimeter of sheet thickness.

The advantages of the heat treatment method according to the invention are mainly that in sheets made of this steel with a min. limit

by min. 10%. This increase in the strength properties of the sheets allows them to be transferred to a higher strength level while maintaining the original level of notch toughness, which means a significant reduction in the weight of structures, etc. Further, for example, the production of sheets with a min. yield strength of 700 MPa does not require alloying of steel with elements such as Cr. Ni and the following additives. Tempering of sheets in quenching presses after hot rolling. The increase in the strength properties of these sheets after annealing/according to the invention reaches a level of a higher strength level, i.e. a min. yield strength of approximately 800 MPa.

The invention has been verified with sheets of thickness 3 to 25 mm.

The heat treatment method according to the invention is illustrated in the following examples.

Example 1

Steel, with a chemical composition of 0.08 to 0.12% carbon by weight,

0.20 to 0.40% silicon, 0.80 to 2.20% manganese, with manganese not exceeding 12 times that of zirconium and 0.005 to 0.025% phosphorus, 0.002 to 0.025% sulfur, 0.01 to 0.06% aluminum, 0.25 to 0.40% molybdenum, 0.05 to 0.10% niobium and 0.06 to 0.16% titanium, was hot rolled in a controlled mode with a thickness of 12 mm. After annealing in a continuous annealing furnace at a temperature of 700°C and a time of 1.3 minutes per mm of thickness.

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yield strength of the used plate in MPa: of 5 scrolls, were.achieved these while Scroll 1 2 3 4 5 Rolled condition 630 657 682 740 812 Annealed condition 760 745 770 838 918 Example 5. Steel,chemical massive composition 0» 05 to 0 .10% carbon

0.20 to 0.40% silicon, 1.60 to 1.80% manganese, with manganese not exceeding 12 times that of zirconium and Salej 0.005 to

0.030% phosphorus, 0.005 to 0.025% sulfur, 0.01 to 0.08% aluminum, 0.20 to 0.35% molybdenum and 0.05 to 0.10% niobium, was hot rolled in a controlled mode to a thickness of 10 mm.

After annealing in a continuous annealing furnace at a temperature of 700°C and a time of 1.2 minutes per 1 mm thickness of the used sheet metal from 5 coils,

the following yield strengths in MPa were achieved: Scroll 1 2 3 4 5 Rolled condition 492 525 556 570 596 Annealed condition 574 590,644 647 662 TRANSFER INVENTION

Claims (1)

No. 3,232,179 used sheet in MPa: from 5 coils, the following limits were obtained Coil 1 2 3 4 5 Rolled condition 630 657 682 740 812 Annealed condition 760 745 770 838 918 Example 2. Steel, chemical composition 0, 05 to 0.10% carbon, 0-20% to 0.40% silicon, 1.60-1.80% manganese, while manganese does not exceed 12 times zirconium, and 0.005-0.030% phosphorus, 0.005-0.025% sulfur, 0.01-0%. , 08% alumina, 0.20 to 0.35% molybdenum, and 0.05 to 0.10% niobium, a 10 mm thick hot-rolled bolavyvalc regime. After annealing in a continuous stitching furnace at 700 ° C and a time of 1.2 minutes for 1 mm ridge of the used sheet of 5 coils, the following yield strengths were achieved in MPa: Roll 1 2 3 4 5 Rolled condition 492 525 556 570 596 Annealed 574 590 DESCRIPTION OF THE INVENTION A method of heat treating a sheet of structurally weldable low carbon microalloyed steel in hot rolled or hot rolled products, with a chemical composition of up to 0.14% carbon, up to 0.9% silicon, 0.005 to 0.04% phosphorus, 0.002 to 0.035% sulfur, 0.06 to 0.2% zirconium, 0.8 to 4% 0% manganese, and to about 0.3% hliriika, to 0.6% medium. From 0.05 to 0.9% molybdenum, up to 1% chromium and up to 4.0% nickel, in a total combination of up to 6.0% or Saline 0.005 to 0.45% of the total combination of niobium, thiate, vanadium, bSA, cerium and lanthanum, characterized in that the cores or articles thereof in the thickness range of 3 to 25 mm are annealed at a temperature of 650 to 750 ° C for a period corresponding to 1.0 to 1.5 minutes per millimeter of sheet metal ridge.