JPS6021318A - Production of tempered high tensile steel - Google Patents

Abstract

PURPOSE:To obtain a high tensile steel material which is hot dipped in a simple installation with a steel material having a low strength as a raw material in the stage of hardening and tempering a structural steel by controlling the cooling rate for hardening and performing the tempering by dipping the steel in a molten metal. CONSTITUTION:For example, an angle steel 1 which is a raw material is put into a high frequency heater 2 by a roller conveyor 5 and is hardened continuously with a cooler 6. The hardening is accomplished by changing the cooling rate for hardening according to the amt. of the hardenability increasing element such as C, Mn or the like contained in the steel material. More specifically, the hardening with this hardening device is accomplished by inputting preliminarily the measured value of the above-described hardenability increasing agent in the steel material to a setter 10, ejecting the cooling water of the amt. and pressure matched with the steel from water feed nozzles 7 and controlling automatically the cooling rate. The hardened steel 1 is subjected to necessary working such as cutting and is dipped in a galvanizing bath, by which the steel is simultaneously tempered and galvanized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing tempered high-strength steel, and more particularly, to a method for manufacturing hot-dip metal-plated high-strength steel for use in steel structures such as steel towers and buildings.

Conventionally, heat-treated (quenched and tempered) high-strength steel for membrane structures has been produced in steel plates with a strength of 80 to 100 KP/-, but steel pipes and sections are generally non-tempered. Only those that are produced. Therefore, except for special uses, steel pipes are 60 to 65 9/ma + shaped steel is 55
Only K9/11 (j) products are commercially available.

This is because the unit price of heat-treated steel is high, and the production of cheap heat-treated steel, especially cheap 70-90Ky/
There was a demand for the development of tempered steel pipes and sections with a strength of -.

This invention was made in view of the above circumstances, and its purpose is to provide a heat-treated high-strength steel that can be made from low-strength steel and coated with hot-dip metal at a low cost using simple equipment. The aim is to propose a manufacturing method. The gist is to heat the steel material using high frequency or other known methods, and then harden the steel material by controlling the cooling rate depending on the amount of elements that increase hardenability, such as carbon and manganese, contained in the steel material, and then melt the steel material. Tempering characterized by immersing the metal in a tempering process, simultaneously applying metal plating and leaving it to cool, or cooling with water or other cooling medium as necessary to prevent tempering brittleness. This is a method of manufacturing high-strength steel.

In this manufacturing method, - Rolled steel materials for shell structure 8841 to 885
5. Alternatively, the raw material may be 5M50 rolled steel for welded structures. Conventionally, general steel manufacturers have carried out quenching and tempering of structural steel by keeping the quenching and cooling conditions constant and changing the tempering conditions depending on the purpose of use. In this manufacturing method, the cooling rate of hardening and hardening is changed depending on the amount of hardenability-enhancing elements in the raw steel material, and tempering is performed by immersing it in molten metal such as molten zinc (temperature 455-470°C). Further, if necessary, the material is cooled with a cooling medium such as hot water to prevent temper brittleness. According to this manufacturing method, 80Kp/- galvanized high tensile strength steel can be obtained at low cost using 5M50 as a raw material. The conventional commercial price for 5M50 is approximately 110,000 to 120,000 yen/ton, 80K.
The price of p/- high tensile strength steel is about 190,000 to 250,000 yen/ton.

This will be explained below using the drawings. FIG. 1 shows this manufacturing method in the order of steps. For example, as shown in FIG. 1A, an angle iron 1 is used as a raw material and heated to about 00° C. by a high-frequency heating device 2. (b) As shown in the figure, the heated section steel 1 is rapidly cooled and hardened by controlling the cooling rate depending on the content of carbon, manganese, etc., by jetting cooling water or using another cooling medium. The angle iron 1 that has been hardened is subjected to material processing such as cutting, drilling, bending, etc., as shown in Figure (C), depending on the purpose of use. Next, in figure (d), hot-dip galvanizing bath 3 (455-4
At the same time, the angle steel 1 is immersed in a hot water bath 4 of 60 to 70°C as shown in Fig. 70°C (e) to cool it and prevent tempering brittleness. The result is heat-treated high-strength steel that is hot-dip galvanized.

In Fig. 1, the material processing step (Fig. (C)) may be performed before the high-frequency heating step (Fig. (a)) or after the tempering step (Fig. (e)). It's okay.

FIG. 2 shows an example of an induction hardening apparatus used in the present invention. The angle iron 1, which is a raw material, is placed on a roller conveyor 5, heated by a high-frequency heating device 2, and then continuously fed into a cooling device 6. The cooling device 6 has a water supply nozzle 7 at the upper part of the inner side and a drainage chute 8 at the lower part, and cools and hardens the section steel 1 running inside by injecting cooling water sent from the water supply pipe 9 from the water supply nozzle 7. . The cooling device 6 includes a setting device 10. Water supply controller 11. A driving device 12 is attached and connected to the water supply pipe 9 at a regulating valve 13 provided in the water supply pipe 9. 4 This hardening device measures the content of hardenability increasing elements such as carbon and manganese in the raw material angle steel in advance, inputs this value into the setting device 10, and matches the raw material angle steel 1. Quenching can be performed by injecting cooling water at a certain amount and pressure from the water supply nozzle 7 and automatically controlling the cooling rate.

The present invention has the above configuration, and in this manufacturing method, a raw steel material is heated and hardened by high frequency or other known methods, and then immersed in a molten metal bath to be metal plated for tempering. Therefore, the two steps of tempering and hot-dip metal plating can be reduced to one step. In addition, since the cooling rate for quenching is controlled according to the amount of hardenability-enhancing elements contained in the raw material, even though the tempering treatment conditions are limited in the molten metal bath, it can be adjusted to fit the raw material. Can be hardened and tempered.

As described above, this manufacturing method uses low-strength steel as raw material,
It is possible to obtain high tensile strength steel materials coated with hot-dip metal at low cost using simple equipment.

[Brief explanation of drawings]

Figure 1 (a), (b), (C), (d), and (e) are schematic diagrams showing this manufacturing method in the order of steps. (C) is a material processing step, (d) and (e) are tempering steps consisting of immersion in a molten zinc bath and hot water bath, and FIG. 2 is a schematic diagram showing a partial cross section of an induction hardening device. Tonne shaped steel, 2. High frequency heating device, 3. Hot dip galvanizing bath, 4. Hot water bath, 5. Roller conveyor, 6. Cooling device, 7. Water supply nozzle, 8.
・Drainage chute, 9.. Water supply pipe, 10.. Setting device, 11.. Water supply controller, 12.. Drive device. 13...Adjustment valve.

Claims (2)

[Claims] (1) A steel material is heated by high frequency or other known methods, and the cooling rate is controlled depending on the amount of hardenability-increasing elements such as carbon and manganese contained in the steel material, and the steel material is quenched. A method for producing heat-treated high-strength steel, which is characterized by immersing it in a liquid, tempering it, and simultaneously applying metal plating. (2) The method for producing tempered high-strength steel according to claim 1, characterized in that, following the tempering treatment, cooling is performed with water or other cooling medium to prevent temper brittleness.