JP2010053391A - Hot-forged part for connecting rod excellent in fracture-partition property, and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hot-forged part for connecting rod excellent in fracture-partition property. <P>SOLUTION: The hot-forged part for connecting rod excellent in the fracture-partition property, is composed, by mass, of 0.1-0.6% C, ≤1.0% Si (not contain 0%), 0.5-2.0% Mn, 0.01-0.08% P, 0.01-0.20% S, ≤0.4% V (not contain O%), ≤1.0% Cr (not contain 0%), ≤0.05% Al (not contain 0%), 0.01-0.1% Nb and the balance Fe with inevitable impurities, and is characterized in that in the micro-structure, a grain size number of the prior austenite grain is No.7 or less, and also the prior austenite grain is not applicable to duplex grain regulated in JIS G 0551. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a steel suitably used for the manufacture of a connecting rod (hereinafter may be abbreviated as “connecting rod”) used as a part of an automobile engine or the like.

  An internal combustion engine such as a gasoline engine or a diesel engine uses a connecting rod as a component that connects a piston and a crankshaft and transmits the reciprocating motion of the piston to the crankshaft to convert it into a rotational motion. This connecting rod is a part with a substantially circular through-hole for assembling to the crankshaft, and the through-hole part is separated (divided) into two substantially semicircles in order to facilitate removal during assembly and maintenance. Is configured to do. Of the separated connecting rods, the side directly connected to the piston is called a connecting rod body, and the rest is called a connecting rod cap.

  Such a connecting rod can be manufactured, for example, by subjecting the connecting rod body and the connecting rod cap to hot forging separately and then processing the mating surfaces by cutting. In this case, knock pin processing may be performed as necessary to prevent displacement. However, when such processing is performed, there is a problem that the yield of the material is reduced and the cost is increased due to a large number of steps.

  Therefore, after the connecting rod is integrally hot forged and subjected to machining (through hole formation processing (drilling processing), bolt hole processing, etc. for assembling to the crankshaft), the through hole portion becomes two substantially semicircles. As described above, a method is used in which breakage is divided in the cold (splitting processing), and finally the fractured surface is fitted with the crankshaft interposed therebetween and fastened with bolts for assembly. According to this method, it is not necessary to process the mating surface by cutting the fracture surface.

For example, Patent Documents 1 to 3 are known as steels for connecting rods having excellent fracture splitting properties. In Patent Documents 1 and 2, the fracture splitting property is enhanced by positively adding P. In Patent Document 3, Ti is contained, and austenite grains at the time of hot forging are partially pinned with TiC to be in a mixed grain state to ensure break splitting.
JP 2002-256394 A JP 2003-113419 A Japanese Patent Laying-Open No. 2005-2367

  Even with the methods described in Patent Documents 1 to 3, although the fracture splitting property shows a certain improvement, it cannot be said to be sufficient yet. An object of the present invention is to provide a hot forged part for a connecting rod excellent in fracture splitting property and a manufacturing method thereof.

  In the above Patent Documents 1 and 2, it is recommended that P be positively added in order to ensure break splitting property. P is effective for improving the break splitting property, but if added excessively, the hot workability is lowered.

  Therefore, the present inventor has intensively studied to realize a hot forged part for a connecting rod having excellent fracture splitting property without impairing hot workability. As a result, if Nb is contained as an essential component, the prior austenite grains are coarse and do not correspond to the mixed grains defined in JIS G 0551, it is possible to ensure good fracture splitting property, and further P It was found that the occurrence of cracks during hot working can be reduced because it can be suppressed, and the present invention has been completed.

  That is, the hot forged parts for connecting rods having excellent fracture splitting properties according to the present invention are C: 0.1 to 0.6% (meaning mass%, hereinafter the same), Si: 1.0% or less. (Excluding 0%), Mn: 0.5 to 2.0%, P: 0.01 to 0.08%, S: 0.01 to 0.20%, V: 0.4% or less (0 %), Cr: 1.0% or less (not including 0%), Al: 0.05% or less (not including 0%), Nb: 0.01 to 0.1%, The balance is iron and unavoidable impurities. In the microstructure, the grain size number of the prior austenite grains is 7 or less, and the summary is that the prior austenite grains do not correspond to the mixed grains defined in JIS G 0551.

  The hot forged parts for connecting rods further include (a) Cu: 1.0% or less (not including 0%), Ni: 1.0% or less (not including 0%), and Mo as other elements. : At least one selected from the group consisting of 1.0% or less (not including 0%), (b) Bi: 0.1% or less (not including 0%), Zr: 0.2% or less (0 %), Ca: 0.005% or less (not including 0%), Mg: 0.005% or less (not including 0%), Te: 0.1% or less (not including 0%) And REM: at least one selected from the group consisting of 0.3% or less (not including 0%) may be included.

  The connecting rod of the present invention is manufactured from the hot forged part for a connecting rod.

  The method for producing a hot forged part for a connecting rod according to the present invention comprises hot forging a steel material satisfying the above component composition at a pre-forging heating temperature of 1150 ° C. or higher and a forging end temperature of 950 ° C. or higher. It cools to 500 degreeC with the average cooling rate of 1.5 degrees C / s or less.

  According to the present invention, by containing Nb as an essential component, the prior austenite grains are coarse (grain size number is 7 or less) and do not correspond to the mixed grains defined in JIS G 0551, thereby breaking breakability. It is possible to realize a hot forged part for a connecting rod that is excellent in the quality.

  The hot forged parts for connecting rods and connecting rods of the present invention will be described first from the chemical composition.

C: 0.1 to 0.6%
C is necessary to ensure the strength of the hot forged parts for connecting rods. Furthermore, it is an element that is also effective for improving the break splitting property. Therefore, the C amount is set to 0.1% or more. The amount of C is preferably 0.2% or more, more preferably 0.3% or more. However, if the amount of C is excessive, machinability is reduced. Therefore, the C amount is set to 0.6% or less. The amount of C is preferably 0.55% or less, more preferably 0.5% or less.

Si: 1.0% or less (excluding 0%)
Si is useful as a deoxidizing element when melting steel. Furthermore, it is an effective element for improving the strength of hot forged parts for connecting rods. In order to sufficiently exhibit this effect, the Si amount is preferably 0.05% or more, more preferably 0.1% or more. However, if the amount of Si is excessive, machinability and hot workability deteriorate. Therefore, the Si amount is set to 1.0% or less. The amount of Si is preferably 0.7% or less, more preferably 0.5% or less.

Mn: 0.5 to 2.0%
Mn is useful as an element that can prevent cracking during casting by forming MnS. Furthermore, it is an effective element for improving the strength of hot forged parts for connecting rods. In order to fully exhibit this effect, the amount of Mn was determined to be 0.5% or more. The amount of Mn is preferably 0.7% or more, more preferably 0.9% or more. However, if the amount of Mn is excessive, bainite is generated and machinability is lowered. Therefore, the amount of Mn is set to 2.0% or less. The amount of Mn is preferably 1.8% or less, more preferably 1.5% or less.

P: 0.01 to 0.08%
P is an element necessary for improving the fracture splitting property of the hot forged part for connecting rods. Therefore, the P content is set to 0.01% or more. The amount of P is preferably 0.015% or more, more preferably 0.02% or more (particularly 0.03% or more). However, when the amount of P is excessive, hot workability is reduced. Therefore, the P content is set to 0.08% or less. The amount of P is preferably 0.07% or less, more preferably 0.06% or less.

S: 0.01 to 0.20%
S is an element useful for securing the strength of hot forged parts for connecting rods and improving break splitting property. Therefore, the S amount is set to 0.01% or more. The amount of S is preferably 0.02% or more, more preferably 0.03% or more. However, when the amount of S is excessive, hot workability is reduced. Therefore, the S amount is set to 0.20% or less. The amount of S is preferably 0.1% or less, and more preferably 0.07% or less.

V: 0.4% or less (excluding 0%)
V is an element useful for securing the strength of hot forged parts for connecting rods and improving break splitting. In order to sufficiently exhibit this effect, the V amount is preferably 0.02% or more, more preferably 0.05% or more. However, if the amount of V is too large, the effect is saturated and the cost is increased. Therefore, the V amount is set to 0.4% or less. The amount of V is preferably 0.3% or less, more preferably 0.2% or less.

Cr: 1.0% or less (excluding 0%)
Cr is an element useful for securing the strength of hot forged parts for connecting rods and improving the fracture splitting property. In order to sufficiently exhibit this effect, the Cr content is preferably 0.05% or more, more preferably 0.1% or more. However, if the amount of Cr becomes excessive, the machinability decreases. Therefore, the Cr content is set to 1.0% or less. The amount of Cr is preferably 0.9% or less, more preferably 0.7% or less.

Al: 0.05% or less (excluding 0%)
Al is an element useful as a deoxidizing element. In order to sufficiently exhibit this effect, the Al amount is preferably 0.002% or more, more preferably 0.004% or more. However, if the amount of Al is too large, the effect is saturated and the cost is increased. Therefore, the Al content is set to 0.05% or less. The amount of Al is preferably 0.04% or less, more preferably 0.035% or less.

Nb: 0.01 to 0.1%
Nb is an important element for enhancing the fracture splitting property of the hot forged part for connecting rods in the present invention. Therefore, the Nb amount is set to 0.01% or more. The Nb amount is preferably 0.015% or more, more preferably 0.02% or more. However, if the amount of Nb is too large, the effect is saturated and the cost is increased. Therefore, the Nb amount is set to 0.1% or less. The Nb amount is preferably 0.08% or less, more preferably 0.07% or less.

  The basic component composition of the hot forged part for connecting rods of the present invention is as described above, with the balance being iron and inevitable impurities. As an inevitable impurity, it is naturally allowed that elements brought into the steel (for example, O, N, As, Sb, Sn, Ti, B, etc.) are contained in steel depending on the situation of raw materials, materials, manufacturing equipment, and the like. The Furthermore, the hot forged part for a connecting rod of the present invention may contain the following optional elements as necessary.

Cu: 1.0% or less (excluding 0%),
Ni: 1.0% or less (excluding 0%),
Mo: at least one selected from the group consisting of 1.0% or less (excluding 0%) Cu, Ni, and Mo are all useful elements for securing the strength of hot forged parts for connecting rods, You may make it contain as needed. In order to sufficiently exhibit this effect, the amount of Cu is preferably 0.01% or more, and more preferably 0.05% or more. The amount of Ni is preferably 0.01% or more, and more preferably 0.05% or more. The amount of Mo is preferably 0.01% or more, and more preferably 0.1% or more. However, when the amount of Cu is excessive, hot workability is lowered and the cost is increased. Therefore, the amount of Cu is preferably 1.0% or less, more preferably 0.5% or less. If the amount of Ni is too large, the effect is saturated and the cost increases. Therefore, the Ni content is preferably 1.0% or less, more preferably 0.5% or less. Furthermore, if the amount of Mo becomes excessive, the machinability decreases and the cost also increases. Therefore, the Mo amount is preferably 1.0% or less, more preferably 0.7% or less (particularly 0.5% or less).

Bi: 0.1% or less (excluding 0%),
Zr: 0.2% or less (excluding 0%),
Ca: 0.005% or less (excluding 0%),
Mg: 0.005% or less (excluding 0%),
Te: 0.1% or less (excluding 0%),
REM: At least one selected from the group consisting of 0.3% or less (excluding 0%) Bi, Zr, Ca, Mg, Te, and REM are all useful elements for improving machinability. . In particular, Zr, Ca, Mg, Te, and REM have an effect of improving machinability by spheroidizing MnS. In order to sufficiently exhibit this effect, the Bi amount is preferably 0.001% or more, more preferably 0.01% or more, the Zr amount is preferably 0.01% or more, more preferably 0.05% or more, Ca amount is preferably 0.0001% or more, more preferably 0.001% or more, Mg amount is preferably 0.0001% or more, more preferably 0.001% or more, and Te amount is preferably 0.0001% or more. More preferably, it is 0.001% or more, and the amount of REM is preferably 0.0001% or more, more preferably 0.001% or more. However, even if these elements are excessive, the effect is saturated and the cost is increased. Therefore, the Bi amount is preferably 0.1% or less, more preferably 0.08% or less, and the Zr amount is preferably 0.15% or less, more preferably 0.13% or less (particularly 0.12% or less). The amount of Ca is preferably 0.005% or less, more preferably 0.004% or less (particularly 0.003% or less), and the amount of Mg is preferably 0.005% or less, more preferably 0.004% or less (particularly 0.003% or less), Te amount is preferably 0.1% or less, more preferably 0.05% or less (particularly 0.03% or less), and REM amount is preferably 0.3% or less, more preferably 0. .1% or less (particularly 0.05% or less).

  The component composition of the hot forged part for a connecting rod of the present invention has been described above.

  Next, the microstructure of the hot forged part for connecting rods of the present invention will be described.

[Grade number of former austenite grains: 7 or less]
The relationship between the particle size number of the prior austenite grains and the fracture splitting property will be described with reference to FIG. As shown in Table 1, FIG. 1 shows the grain size number of prior austenite grains for the test pieces after hot forging with Nb content changed to 0.000, 0.006, 0.015, 0.050%. This is a summary of the relationship with the dimensional change during break splitting.

  According to FIG. 1, it can be seen that when the prior austenite grain size is No. 7 or less, the dimensional change is sufficiently reduced, that is, the fracture splitting property is improved. Further, this effect becomes more prominent as the amount of Nb added increases. Therefore, the particle size number of the prior austenite grains was set to 7 or less. The grain size number of the prior austenite grains is more preferably 6 or less (particularly 5 or less). The lower limit of the grain size number of the prior austenite grains is not particularly limited, but may be approximately 3 or more.

[Old austenite grains do not fall under the mixed grains defined in JIS G 0551]
In the present invention, if the prior austenite grains do not correspond to the mixed grains defined in JIS G 0551, within one field of view (1 mm ² ), there are grains having a grain number number that differs by 3 or more from the grain number having the highest frequency. In that case, it means that the area of these grains is less than 20%. By making the prior austenite grains not applicable to mixed grains, it is possible to suppress variation in fracture splitting (evaluated by variation in dimensional change when multiple fracture split tests are performed as shown in the examples described later). can do.

  The hot forged part for a connecting rod of the present invention having the above-described structure can be produced by hot forging and cooling a steel material satisfying the above component composition under the following conditions.

[Heating temperature before forging: 1150 ° C or higher, forging end temperature: 950 ° C or higher]
The hot forged part for a connecting rod according to the present invention contains Nb as an essential element as described above. Usually, steel added with Nb has finer crystal grains due to the pinning effect of Nb carbonitride and the like, and has high toughness. When it is high toughness, the amount of deformation of the hot forged part becomes large at the time of fracture division, and the fracture division property is inferior.

  On the other hand, when Nb is sufficiently dissolved and the pinning effect of Nb carbonitride is not exhibited, the prior austenite grains can be made coarse and do not fall under the mixed grains defined in JIS G 0551. In addition, it is possible to realize an excellent break splitting property with little variation. Therefore, in order to sufficiently dissolve Nb and prevent Nb carbonitride from precipitating, the heating temperature before forging was set to 1150 ° C. or more and the forging end temperature was set to 950 ° C. or more. In the present invention, the heating temperature before forging means the heating temperature of the furnace, and the forging end temperature means the surface temperature of the hot forged part at the end of forging.

  The heating temperature before forging is preferably 1200 ° C. or higher, and the forging end temperature is preferably 1000 ° C. or higher. The upper limit of the heating temperature before forging and the forging end temperature is not particularly limited, but the heating temperature before forging may be 1300 ° C. or less, and the forging end temperature may be 1200 ° C. or less.

  In order to sufficiently dissolve Nb, the holding time at the pre-forging heating temperature is preferably 200 s or longer.

[Average cooling rate from 800 ° C to 500 ° C: 1.5 ° C / s or less]
The hot forged part of the present invention has a substantially ferrite-pearlite structure. When the average cooling rate from 800 ° C. to 500 ° C. becomes too fast, a bainite structure is generated, and the fracture splitting property is inferior. Therefore, the average cooling rate from 800 ° C. to 500 ° C. is set to 1.5 ° C./s or less (more preferably 1.3 ° C./s or less). In order to realize such a cooling rate, it is preferable to perform cooling or air cooling, and when the cooling rate becomes too fast, a step of holding the desired cooling rate may be provided. The lower limit of the cooling rate is not particularly limited, but the cooling rate from 800 ° C. to 500 ° C. may be 0.2 ° C./s or more.

  The structure of the hot forged part of the present invention may be composed only of a ferrite / pearlite structure, or may include a structure such as bainite if the amount is small. It is preferable that ferrite and pearlite contain 90 area% or more (particularly 95 area% or more) in total with respect to the entire structure, and the other structures should be 10 area% or less in total with respect to the entire structure. preferable.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Experimental Example 1 Examination of Component Composition Steel having the chemical composition shown in Table 2 was melted according to a normal melting method, cast and divided, then rolled at a start temperature of 1050 ° C. and an end temperature of 900 ° C., and a steel bar of φ50 mm Got. After cutting the obtained steel bar to a suitable length, it was flattened to a thickness of 25 mm at a heating temperature before forging: 1200 ° C., a holding time at the heating temperature before forging: 1800 seconds, a forging end temperature: 971 ° C. Forging was performed, and cooling was performed so that the average cooling rate from 800 ° C. to 500 ° C. was 0.57 ° C./s. The characteristics of the obtained flat plate were examined as follows. In Table 2, REM used Misch metal containing Ce: 50%, La: 25%, and Nd: 15%.

(1) The grain size number of prior austenite grains and the presence or absence of mixed grains In the cross section at the t / 4 position (t is the plate thickness) of the flat plate, a field of view of 0.63 mm ² was observed with an optical microscope (100 times), The austenite grain size number and the presence or absence of mixed grains were measured according to JIS G 0551. As the crystal grain size number, an average value of those measured for two visual fields was calculated. The presence / absence of mixed grains was measured for two visual fields. The presence / absence of mixed grains is determined when there is a grain with a grain number different by 3 or more from the grain with the largest frequency in two fields of view, and when the area of these grains is less than 20% And the other cases were determined to be mixed.

(2) Breakability (dimensional change)
A flat plate obtained by hot forging was cut and processed into a test piece as shown in FIG. In FIG. 3, (a) is a top view of the test piece, (b) is a side view of the test piece, a is a notch, b is a bolt hole, and c is an arrow indicating the rolling direction. The test piece has a plate shape of 65 mm × 65 mm × thickness 22 mm, and a cylindrical hole of φ43 mm is extracted at the center. A notch a (R 0.2 mm, depth 0.5 mm) is provided at the end of the central hole. The test piece is provided with a bolt hole b (φ8.3 mm) along the rolling direction.

  As shown in FIG. 4, the test piece 6 was set in a press tester (1600 t press) through the holders 3 a and 3 b in the center hole of the test piece 6, and the test piece was broken and divided at a press speed of 270 mm / s. The breaking speed of the test piece is calculated to be about 150 mm / s because the wedge angles of the wedges 4 and 5 are 30 °. And as shown in FIG. 5, the hole diameter difference (L2-L1) before and after the fracture splitting was measured as a dimensional change, and those having a dimensional change of 0.14 mm or less were evaluated as having excellent split splitting ability. “Dimensional change of 0.14 mm or less” is a component composition equivalent to C70S6 of DIN standard used in Europe (0.71% C−0.24% Si−0.49% Mn−0.010% P -0.057% S-0.10% Cr-0.009% Al) steel material, heating temperature before forging 1200 ° C, holding time 1800s, forging end temperature 971 ° C, average cooling rate from 800 ° C to 500 ° C A test piece was prepared as described above at 0.57 ° C./s, and the value (dimensional change: 0.14 mm) obtained by evaluating the fracture splitting property was used as a reference.

  The results are shown in Table 3.

  A3, A4, and A6 to 17 are examples in which the component composition satisfied the requirements of the present invention, so there was no mixed grain and the fracture splitting property was good.

  A1 to A2, A18, A20, and A22 are examples in which Nb is not contained or the amount of Nb is small, so that the fracture splitting property is lowered.

  A19 and A21 are examples in which cracking occurred during forging because S or P was excessively contained.

  A5 is an example in which Nb is excessively contained, but even if it contains more than 0.1% of Nb, the effect of fracture splitting is equivalent to that of the other examples, leading to an increase in cost. .

Experimental Example 2 Examination of manufacturing conditions (1)
0.34% C-0.25% Si-1.06% Mn-0.048% P-0.055% S-0.093% V-0.35% Cr-0.020% Al-0. A flat plate was prepared under the conditions shown in Table 4 in the same manner as in Experimental Example 1 using 050% Nb. Measurement was performed in the same manner as in Experimental Example 1 with respect to the particle size number of the prior austenite grains, the presence or absence of mixed grains, and the dimensional change at the time of measurement fracture division. Regarding the dimensional change, each No. 5 samples were measured.

  The results are shown in Table 4 and FIG.

  Since B1 is appropriately controlled forging conditions, the grain number satisfies the requirements of the present invention, and there is no mixed grain. Therefore, B1 is an example in which good fracture splitting with little variation can be realized.

  B2 and B3 are examples in which the pre-forging heating temperature and the forging end temperature were low, because the prior austenite grains were refined due to the pinning effect of Nb carbonitride, resulting in a decrease in fracture splitting properties and a mixed grain state. There was variation in the dimensional change.

  In B4, since the pre-forging heating temperature and the forging end temperature were low, precipitation of Nb carbonitride resulted in uniform refinement of the prior austenite grains and no mixed grains, so the variation in dimensional change was small. However, this is an example in which the value of the dimensional change amount itself is large, that is, the fracture splitting property is lowered.

Experimental Example 3 Examination of manufacturing conditions (2)
0.34% C-0.25% Si-1.06% Mn-0.048% P-0.055% S-0.093% V-0.35% Cr-0.020% Al-0. Measurement was performed in the same manner as in Experimental Example 1 except that 050% Nb was used and hot forging and cooling were performed under the conditions shown in Table 5.

  The results are shown in Table 5.

  C4 to C8 are examples in which there are no mixed grains and fracture splitting is good because the production conditions of the present invention are satisfied.

  C1 to C3 are examples in which the pre-forging heating temperature satisfies the requirements of the present invention, but the forging end temperature was low, so the particle size number was increased and the fracture splitting property was lowered.

  C9 is an example in which the average cooling rate from 800 ° C. to 500 ° C. was high, so that bainite was generated and the fracture splitting property was lowered.

FIG. 1 is a graph showing the relationship between the crystal size of the prior austenite grains and the dimensional change during fracture division. FIG. 2 is a graph showing the relationship between the pre-forging heating temperature, the dimensional change during fracture division, and the presence or absence of mixed grains. FIG. 3 (a) is a schematic top view of a test piece used in the fracture splitting test, and FIG. 3 (b) is a schematic side view of the test piece. FIG. 4 is a schematic view of the apparatus for explaining the method of the fracture split test. FIG. 5 is a schematic top view of the test piece before and after the fracture split test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Press 2 Support stand 3a, 3b Holder 4, 5 Wedge 6 Test piece

Claims (5)

C: 0.1 to 0.6% (meaning mass%, hereinafter the same),
Si: 1.0% or less (excluding 0%),
Mn: 0.5 to 2.0%
P: 0.01 to 0.08%,
S: 0.01 to 0.20%,
V: 0.4% or less (excluding 0%),
Cr: 1.0% or less (excluding 0%),
Al: 0.05% or less (excluding 0%),
Nb: 0.01 to 0.1% is contained,
The balance is iron and inevitable impurities,
Hot forging for connecting rods with excellent fracture splitting characteristics, characterized in that the grain size number of the prior austenite grains is 7 or less and the prior austenite grains do not correspond to the mixed grains defined in JIS G 0551 in the microstructure. parts. Furthermore,
Cu: 1.0% or less (excluding 0%),
Ni: 1.0% or less (excluding 0%),
Mo: 1.0% or less (excluding 0%)
The hot forged part for a connecting rod according to claim 1, comprising at least one selected from the group consisting of: Furthermore,
Bi: 0.1% or less (excluding 0%),
Zr: 0.2% or less (excluding 0%),
Ca: 0.005% or less (excluding 0%),
Mg: 0.005% or less (excluding 0%),
Te: 0.1% or less (excluding 0%),
REM: 0.3% or less (excluding 0%)
The hot forged part for a connecting rod according to claim 1, comprising at least one selected from the group consisting of:   The connecting rod manufactured from the hot forging components for connecting rods in any one of Claims 1-3. A steel material satisfying the component composition according to any one of claims 1 to 3,
Hot forging with a pre-forging heating temperature of 1150 ° C or higher and a forging end temperature of 950 ° C or higher,
A method for producing a hot forged part for a connecting rod, characterized by cooling from 800 ° C. to 500 ° C. at an average cooling rate of 1.5 ° C./s or less.

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