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Hot-rolled steel and steel part

A component and steel technology, applied in the direction of anti-centrifugal rotating parts, mechanical equipment, shafts and bearings, etc., can solve the problem of increased shape deformation of the sliding part of the connecting rod, inability to apply high-strength connecting rods, low yield specific tensile strength, etc. Improve economic efficiency, reduce plastic deformation, and improve machinability

Inactive Publication Date: 2019-05-24
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, since the structure of C70S6 is coarser than the ferrite-pearlite structure of medium-carbon non-quenched and tempered steel, which is a common steel for connecting rods, there is a problem that the yield ratio (yield strength / tensile strength) is low , cannot be applied to high-strength connecting rods that require high bending strength
However, when the ferrite fraction of the steel is increased, the ductility of the steel increases, and the amount of plastic deformation near the fracture surface increases when the fracture is separated. The shape deformation of the connecting rod sliding part of the pin part of the crankshaft increases, and the roundness decreases
As explained above, there is a contradictory relationship between the improvement of fitting properties due to the enlargement of fracture unevenness and the prevention of chipping and cracks, and the achievement of both cannot be solved by existing processes

Method used

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Examples

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Embodiment 1

[0112] Converter smelted steel having the composition shown in Table 1 and Table 2 was cast by ingot casting process, and then made into a 162 mm square billet through a billet rolling process, and further hot rolled to make a 56 mm diameter billet. steel bar shape. When the billet is hot-rolled into a round bar shape, the total reduction of area is set to 90%, and the reduction of area in the temperature range of 1000° C. or lower is set to 80%. In addition, the sign of "-" in a table|surface shows that the content of the element related to the place where a sign is described is below a detection limit (impurity level). The heating temperature and heating time of the steel ingot before billet rolling were 1270°C and 140 minutes, respectively, and the heating temperature and heating time of the steel billet before hot rolling were 1240°C and 90 minutes, respectively. The underlined values ​​in Table 2 are within the range of the present invention.

[0113] Mn contained in th...

Embodiment 2

[0153] Steel No.H-2 and Steel No.H-3 having the same chemical composition as Steel No.H recorded in Table 1 were produced under the conditions described in Table 5, and the steels that satisfied the present invention contained in these steels were measured. The average number density of Mn sulfides specified by the equivalent circle diameter and the specified aspect ratio (Mn sulfide number density). The "total reduction of area" in Table 5 is the total reduction of area (%) during hot rolling, and the "reduction of area below 1000°C" is the total reduction of area during the period when the temperature of the steel during hot rolling is 1000°C or lower. Ratio (%), "Mn sulfide number density" is the number density (number / mm 2 ). The production conditions not described in Table 5 were set to be the same as those of Production Nos. 1 to 33.

[0154] [table 5]

[0155]

[0156] As shown in Table 1, the Mn sulfide number density of Steel No. H was within the range of the pr...

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Abstract

The hot-rolled steel according to an embodiment of the present invention has a prescribed chemical component that comprises 0.0001-0.0050 mass% of Bi. At least 90 area% of the metal structure is madeof ferrite and pearlite. The average number density of Mn sulfides, which are elongated in the rolling direction and have an aspect ratio of greater than 10 to 30, measured in cross-sections parallelto the rolling direction is 50-200 per mm<2>.

Description

technical field [0001] The present invention relates to hot-rolled steel products. [0002] this application claims priority based on Japanese Patent Application No. 2016-191456 for which it applied to Japan on September 29, 2016, and uses the content here. Background technique [0003] Engine parts and running part parts of automobiles are obtained by forming steel by hot forging, and optionally performing heat treatment such as quenching and tempering (hereinafter referred to as quenching and tempering). A tempered part is called a tempered part, and a non-tempered part is called a non-tempered part. In any case, the required mechanical properties of the component for the application are ensured. [0004] As an example of a component for an automobile engine, a connecting rod can be cited. This component is a component that transmits power when converting the reciprocating motion of the piston into the rotational motion performed by the crankshaft in the engine. The co...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/00C22C38/60C21D8/06
CPCC22C38/60C22C38/24C22C38/26C22C38/28C22C38/32C22C38/34C22C38/001C22C38/002C22C38/02C22C38/04C21D2211/005C21D2211/009C21D8/065F16C9/045C21D2211/004F16C2220/44F16C2204/62F16C2204/64C21D8/06
Inventor 吉田卓寺本真也志贺聪久保田学长谷川一水上英夫
Owner NIPPON STEEL CORP
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