KR880001121B1 - Method for manufacture wire rod of used arc welding - Google Patents

Abstract

Processing method of wire rod for CO2 gas sheilded arc welding comprises (i) heating step of a billet to 1200-1250 deg.C, (ii) rolling step of the billet at high speed of 60m/sec or more, (iii) rapid cooling step of the rolled wire rod to 800-850 deg.C, and (iv) coiling step of the wire rod with cooling slowly to 400 deg.C at the cooling rate of 2-3 deg.C/sec. The composition of the billet is 0.10-0.13 wt.% C, 0.70-1.0 wt.% Si, 1.2-1.5 wt.% Mn, up to 0.012 wt.% P, up to 0.025 wt.% S, up to 0.04 wt.% Cr, up to 0.02 wt.% Ni, up to 0.02 wt.% Cu, 0.01-0.02 wt.% Ti and the balance Fe.

Description

Method for manufacturing wire rod for carbon dioxide arc welding by controlled cooling

1 is a schematic plan view of a control cooling system used in the present invention.

The present invention relates to a method for producing a carbon dioxide arc welding wire rod excellent in cold workability.

Carbon dioxide arc welding wire has been used in the welding of iron or steel, high strength steel with high strength by adding a small amount of mild steel or alloying elements, and the surface hardening welding material that grows the surface of wear parts with hard metal. Since the welding wire used is characterized by 0.9-1.6 mm ψ, the carbon dioxide arc welding wire which is its material has been required to have excellent cold workability. However, carbon dioxide arc welding wire is a low carbon steel, which is high in manganese (Mn) and silicon (Si), and has a high amount of low carbon martensite even though it regulates impurities and controls rolling conditions and cold temperatures. In the case of embedded ferrite structure, these structures act as different phases during cold working and become stress concentration points around low-carbon martensite, causing disconnection. After the finalization, the final freshness is used for characterization. For this reason, not only increases the manufacturing cost but also deteriorates the toughness by coarsening of the weld metal after welding. Therefore, the present invention burnt by adding a small amount of titanium (Ti) to the carbon dioxide arc welding steel to solve this problem. Carbon dioxide arc welding wire rod method for carbon dioxide arc arc welding, which is performed by controlled cooling to precipitate nitride at austenite grain boundary to suppress grain growth and increase ferrite formation position by grain refinement. It is used for arc welding of carbon dioxide gas of MG / mm2 fixed steel.

The configuration of the present invention in more detail as follows. In the present invention, carbon: 0.10-0.13%, silicon: 0.70-1.0%, manganese: 1.2-1.5%, phosphorus: 0.012% or less, sulfur: 0.025 or less, chromium: 0.04% or less, nickel: 0.02% or less, copper: 0.02 % Or less, Titanium: Billet containing 0.10-0.02% is heated to 1200-1250 ℃, high-speed rolling over 60m / sec, and then the rolled product is rapidly sprayed by water spray within the range of 800-850 ℃. Cooling and winding up to 400 ℃ characterized in that the slow cooling at 2-3 ℃ / sec cooling rate.

Hereinafter, the present invention will be described in detail. First, the component range of the present invention will be described. Carbon increased the strength but lowered the ductility and toughness, and in particular the weldability, so the upper limit was made 0.13%. Silicon is needed to increase strength and in many cases ductility is reduced, but the upper limit is 1.0% to prevent bubble generation by carbon monoxide decomposed in high-temperature arc of carbon dioxide gas, which is a protective gas during welding, and to perform proper deoxidation reaction. Manganese not only secures strength and toughness, but also improves hardenability, but the upper limit is 1.5% to ensure the strength of the weld metal after intermetallic welding, which regulates the amount of carbon that loses weldability. Phosphorus is regulated below 0.012% because it lowers toughness and affects cold working. On the other hand, Cu reduces the weldability, so it is regulated to 0.02% or less, and Cr is added to a small amount of Cr less than 0.04% to improve the mechanical properties of the weld metal, and Ni is added to 0.02% or less. hardening). Titanium suppresses grain growth by titanium nitride (TiN) precipitated at the austenite grain boundary during high temperature heating, and promotes the formation of fine ferrite structure during cooling after rolling to improve strength and toughness. In particular, during welding, the toughness of grains as well as heat affected zones are improved by carbonitrides such as TiC and TiN, and the affinity with carbon, oxygen, sulfur, and nitrogen is large. Is getting rid of. For this purpose, the additive component range was less than 0.02%. Next, a rolling and cooling method of the present invention will be described. In general, when rolling at a high temperature, recrystallization occurs depending on conditions such as rolling temperature and speed deformation.

The present invention accelerates such recrystallization and performs high-speed rolling of the billet of the above composition heated to 1200-1250 ° C. at a rolling speed of 60 m / sec or more. On the other hand, when the rolling temperature is increased during rolling to increase the amount of deformation, it is easy to recrystallize, so that the present invention utilizes the heat of rolling generated during rolling, so that the final finishing stand by high-speed rolling at a rolling speed of 60 m / sec or more. The temperature of the rolled material can be maintained at 1100-1150 ° C which is a high temperature austenite single phase zone.

The rolled material thus rolled suppresses grain growth of austenite and is rapidly cooled to 800-850 ° C. by low water spray. This temperature range is the austenite single phase zone, which allows the most austenitic grains to be retained. On the other hand, the cold-cooled rolled material is wound in a coil form, and then 400 ° C. at 2-3 ° C./sec, which is a cooling rate capable of suppressing formation of bareite or martensite, which is a supercooled structure, on a continuously moving conveyor. Cool slowly to the vicinity.

1 is a schematic plan view of a device suitable for carrying out the present invention, where 1 is a heating furnace, 2 is a horizontal ball rolling stand (25 stands), 3 is a water cooling zone, 4 is a winder, and 5 is a conveyor. to be.

In the carbon dioxide arc wire produced by the method of the present invention as described above, the ferrite is mainly composed of pearlite (Pearlite) and low-carbon martensite as the main structure, but the cold line was possible to less than 0.9㎜ψ.

Table 1 shows the composition of the carbon dioxide arc welding wire produced by the method of the present invention and the characteristics of the product of each composition are shown in Table 2.

TABLE 1

TABLE 2

Claims (1)

Carbon: 0.10-0.13%, Silicon: 0.70-1.0%, Manganese: 1.2-1.5%, Phosphorus: 0.012% or less, Sulfur: 0.025 or less, Chromium: 0.04% or less, Nickel: 0.02% or less, Copper: 0.02% or less, Titanium: Bilvet containing 0.10-0.02% is heated to 1200-1250 ℃, high-speed rolling at 60m / sec or more, and then the rolled product is rapidly cooled in the range of 800-850 ℃ and wound up to 400 ℃. A method for producing a carbon dioxide arc welding wire rod, characterized by slow cooling at a cooling rate of 3 ° C / sec.

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