The method of thermo-mechanical processing of metal

 

(57) Abstract:

The invention relates to ferrous metallurgy, in particular to the manufacture of heat-treated rod reinforcing steel in large profiles using the heat rolling heating during thermal hardening steel in the flow medium section mills. Object of the invention is the possibility of obtaining high strength and plastic characteristics of the steels that do not contain costly and scarce alloying elements such as Mn, Ni and others, as well as the ability to manufacture high-strength reinforcing steel in large profiles on medium section mills. The technology of thermo-mechanical processing of metal, mostly bar reinforcement of large profiles, using the heat rolling heating includes hot rolling, pre-cooling of the roll to temperatures not lower than Ar3, the final rolling in this temperature range, the cyclic cooling surface with a number of cycles equal to two, interim and final tagrename surface, with the first cycle cooling surface of the roll is carried out to a temperature below the 50oC or equal to the minimum temperature stability deformed Austen is thus deformed austenite, and the second cycle cooling of the surface is carried out to a temperature below 100-200 MnoC with final annealing the surface to a temperature below the AC1 point and final cooling. table 1.

The invention relates to ferrous metallurgy, in particular to the manufacture of heat-treated rod reinforcing steel in large profiles using the heat rolling heat, and can be used in thermal hardening steel in the flow medium section mills.

Known methods of heat treatment of steel. For example, a known method of thermal processing of metal using heat rolling heat, including hot rolling, circular surface cooling with a number of cycles equal to two, interim and final tagrename surface temperature below the Ac1 point and final cooling, with the first cycle of hypothermia is carried out in the course of time (0,04-0,10)D with intermediate heating is carried out in a period of 1.0 to 1.8, and the second cycle cooling is performed in the alignment mode during the time of 0.015 to 0.05)D, where D is the diameter of the roll in mm [1].

Closest to the claimed method according to technical essence and the achieved positive the store hot rolling, pre-cooling of roll up to temperatures of Ar3 + (20-50)oC with exposure (0,025-0,115)D, cyclic cooling surface over time (0,015-0,035)D with up to temperatures of Mn + (20-100)oC in each cycle when the number of cycles of at least two interim and final tagrename surface to temperatures Ac1 - (20-100)oC and the final cooling, where D is the diameter of the roll in mm [2].

The disadvantage of this method is the low level of strength, especially plastic characteristics when used to obtain heat-treated rolled in a large profiles. For example, testing of valves large profile, manufactured by known methods, for cold bend showed a negative result. In addition, the known methods do not allow to receive high consumer properties of the reinforcement profiles with a diameter more than 25 mm on plain carbon steels, for example, article PS.

The task of the invention is the possibility of obtaining high strength characteristics of the steels that do not contain costly and scarce alloying elements such as Mn, Ni and others, as well as the ability to manufacture high-strength heat-treated armaturniy fact, in a known method of processing steel hot rolling heating, including hot rolling, pre-cooling of the roll to temperatures not lower than the Ar3 cyclic cooling surface with a number of cycles equal to two, interim and final tagrename surface temperature below Ac1 and final cooling, according to the invention pre-cooling of the roll to temperatures not lower than Ar3 is carried out in the course of time (0,25-0,35)D (where D is the diameter of the Bicycle in mm) before the end of the rolling process, and then spend the final rolling in this temperature range, and the first cycle cooling surface of the roll is carried out to a temperature below the 50oC or equal to the minimum temperature stability of deformed austenite with intermediate annealing the surface to temperatures above 50-150oC minimum temperature stability of deformed austenite, and the second cycle cooling of the surface is carried out to a temperature below 100-200 MnoC.

It was established experimentally that in order to obtain uniform fine-grained structure in the cross section of roll in the finished profile is necessary in the hot rolling process, namely before the finishing car is grewe (1050 20oC) to temperatures lower boundary of the austenitic region, but not lower than the Ar3 to ensure deformation hardening of austenite and delay recrystallization processes. When pre-cooling in the course of time more than 0,35 D c flow recrystallization processes and decreases the effect of strain hardening of austenite. When cooled in the first cycle to temperatures above the temperature minimum resistance of the deformed austenite, followed by annealing the surface to temperatures above the minimum resistance of more than 150oC the finished steel is not provided the desired level of strength characteristics. To obtain high strength characteristics in combination with high ductility cooling in the first cycle should be to temperatures not lower than 50oC minimum resistance of the deformed austenite to ensure thawing of the surface of roll due to internal heat to temperatures not less than 50oC higher than the minimum stability. This will allow you to get a fine bainite structure at greater depth on the diameter of the roll, providing a high plastic properties of metal. The second cycle of hypothermia on top of the article to pass the high holiday of the metal at the temperature equalization between the center and the surface during the final annealing of the surface and therefore will allow while maintaining the high plasticity of finished steel to achieve high strength.

The proposed method of thermomechanical processing of reinforcing steel with specified set of, sequence of operations and the selection of intervals of the characteristic values in the specified range of their changes ensures the achievement of the technical result consists in providing strength and plastic characteristics of finished steel from ordinary carbon steels in a large cross-section through the creation of technology and thermomechanical processing of reinforcing steel large profiles.

This technical result is achieved by solving the problem on inventive step, for example, selection of hot rolling conditions with pre-cooling, and the temperature within the cooling cycles and intermediate annealing the surface of the roll that does not follow from the prior art.

The implementation of the method of thermomechanical processing of reinforcing steel in large profiles was carried out as follows.

Example. In the medium section mill of JSC "ZSMK" in mill 450 conducted pilot testing of the proposed method thermomechanical processing bar reinforcement steel PS N 32 industrial melting.

ortom mill 450, before the last two stands (finishing) conducted preliminary cooling of the roll to a temperature of 940 20oC for a time of 0.3 D (9,6). Then there was the final rolling at this temperature cyclical cooling of the two cycles. The first cycle of hypothermia was performed to a temperature of 530oC, followed by intermediate annealing the surface to a temperature of 650oC, the second cycle of the cooling surface of the roll was carried out before the temperature of 300 30oC, final annealing the surface to a temperature of 530 30oC. Final cooling was carried out on the air.

The proposed method has been tested several modes, reducing the temperature of the roll before the finishing rolling to 940 20oC, subcooling the surface of the roll in the second cycle to a temperature of 300 30oC, the final heating the surface to a temperature of 530 30oC and the time taken for pre-cooling, the temperature of the first cycle of hypothermia and intermediate annealing the surface of the roll in the claimed range of their changes beyond the boundary values. After the implementation of these modes were determined by tensile strength, ultimate techenie the results of industrial tests are shown in table. The table shows that the optimal method of thermo-mechanical processing of metal are modes in examples 1-3.

The proposed method of thermo-mechanical processing of metal provides the achievement of the technical result consists in providing strength and plastic characteristics of the rebar large profile from low-carbon steel is not due to the alloying elements, and through the creation of technology thermomechanical processing of steel. For example, from the data table shows that in the manufacture of heat-treated reinforcing steel large profile of the proposed method obtained the high strength characteristics of the metal (tensile strength 71,5-76,0 kgf/mm2the yield of 55.5-58,0 kgf/mm2while maintaining a high plasticity at the level of 19%). Metal reinforced for modes that deviate from the proposed limits of the parameter values, on the one hand, having a sufficiently high tensile strength, has a high fragility, on the other hand, having a normal plasticity, does not reach the required strength class. These data are confirmed by an act of industrial tests.

The proposed method is industrially applicable in metallurgical preddie. For example, the use of this method in the manufacture of heat-treated bar reinforcement in medium section mill 450 JSC "ZSMK" showed high efficiency technologies.

Sources of information

1. RF patent N 2081189, MKI C 21 D 1/02, 1997.

2. RF patent N 2081182, MKI 21 D 1/02, 1997.

The method of thermo-mechanical processing of metal, mostly bar reinforcement of large profiles, using the heat of the rolling heat, including hot rolling, pre-cooling of the roll to temperatures not lower than the Ar3 cyclic cooling surface with a number of cycles equal to two, interim and final tagrename surface temperature below AC1 and final cooling, characterized in that the preliminary cooling of the roll to temperatures not lower than the Ar3 over time (0,25-0,35)D spend before the end of the rolling process, and then spend the final rolling in this temperature range, and the first cycle cooling surface of the roll is carried out to a temperature below 50C or equal to the minimum temperature stability of deformed austenite with intermediate annealing the surface to temperatures above 50-150C minimum temperature stability is With, where D is the diameter of the rent in mm.

 

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