Hollow member and method for manufacturing same
A manufacturing method, hollow technology, applied in the direction of manufacturing tools, furnace types, furnaces, etc., can solve the problems of decreased fatigue durability and inability to obtain surface hardness, and achieve the effect of suppressing the decrease of quenching hardness
Inactive Publication Date: 2012-06-20
JFE STEEL CORP
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Problems solved by technology
When decarburization occurs, the predetermined surface hardness cannot be obtained, resulting in a decrease in fatigue durability
Method used
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Embodiment
[0100] A hot rolled steel sheet having a composition shown in Table 1 was used as a raw material. These raw materials are subjected to continuous cold forming at a low temperature to form a substantially cylindrical open pipe, and then the ends of the open pipe are butted and welded by high-frequency resistance. welding) for resistance welding to form a resistance welded steel pipe (outer diameter 30mm × wall thickness 6mm). In addition, for a part, hot-rolled steel sheet was used as the raw material, and an open pipe was formed by cold forming in the same manner, and then resistance welding was performed to manufacture an outer diameter of 89mm. ×The main pipe with a wall thickness of 6.2mm is further heated to 950°C, and the final rolling temperature is 800°C for reducing rolling to form an outer diameter of 30mm ×Steel pipe with a wall thickness of 6mm. Among them, during resistance welding, various changes were made to the welding conditions, and as shown in Table 2 ...
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Abstract
A method for manufacturing a hollow member excellent in durability is provided. Specifically, a seam-welded steel pipe made of a steel sheet and having a low-carbon layer width 2h is subjected to quenching in a way that the pipe is heated to a heating temperature T(K) over the Ac3 transformation point at a heating rate Vh(K / s), in no time cooled to a quenching start temperature Tq(K) at a primarycooling rate Vc(K / s), and secondarily cooled (quenched). The heating rate Vh, the highest heating temperature T, and the primary cooling rate Vc are regulated so that formula (1) below may be satisfied (in the formula, Co (mass%): the content (mass%) of C in the steel sheet), t: the diffusion time (s), t=50 / Vh+50 / Vc+k, Vh: heating rate (K / s), Vc: the primary cooling rate (K / s), k: the soaking time (s), D: the diffusion coefficient (m2 / s), D=Doexp(-Q / RT), Do: 4.7OE0-5 (m2 / s), Q=155 (kJ / mol K), R=8.31 (J / mol K), T: the highest heating temperature (K)). The quenching start temperature Tq is overthe Ar3 transformation point. The lowering of the quenching hardness of the seam-welded portion is reduced, and the durability of the member after the heat treatment is significantly improved.
Description
technical field [0001] The present invention relates to an electric resistance welded steel pipe for hollow article suitable for uses such as a stabilizer and a method for manufacturing the same, and particularly relates to rapid heating for a short time The strength of the resistance welded portion after the heat treatment is improved. Background technique [0002] In recent years, from the viewpoint of global environmental protection, the emission gas standards of automobiles have been gradually strengthened, and the weight reduction of automobile bodies is being promoted to improve fuel consumption. As one method of reducing the weight of a vehicle body, a method of changing solid-core parts to hollow parts has recently been tended to be adopted. This tendency is no exception to the stabilizer (stabilizer) that suppresses the rolling of the car body (automobile body) when cornering or improves the running stability at high speed. The weight of the vehicle body has been ...
Claims
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IPC IPC(8): C21D9/08C21D9/50C22C38/00C22C38/14C22C38/58
CPCC22C38/14C22C38/02C21D2211/008C22C38/06C21D1/25C21D9/50C21D9/08C22C38/04C22C1/002C22C38/001C22C1/11C22C38/002
Inventor 河端良和坂口雅之坂田敬
Owner JFE STEEL CORP