JP2004307930A - Non-heat treated steel to be hot-forged for connecting rod - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide a non-heat treated steel to be hot-forged for a connecting rod, which reliably acquires high yield strength and fatigue strength even if thermal refining treatment is omitted after hot forging, and is constituted only by inexpensive elements without containing expensive V. <P>SOLUTION: The non-heat treated steel to be hot-forged for the connecting rod has a composition comprising, by wt.%, less than 0.15-0.35% C, more than 1.2% but 2% or less Si, 0.5-1.5% Mn, more than 0.05% but 0.2% or less P, 0.01-0.5% Cu, 0.01-0.5% Ni, 0.01-1% Cr, 0.001-0.01% s-Al, 0.005-0.035% N and the balance Fe with unavoidable impurities, while satisfying the expression 1: 0.6≤Ceq≤0.85 (wherein Ceq=C+0.07×Si+0.16×Mn+0.61×P+0.19×Cu+0.17×Ni+0.2×Cr), the expression 2: α>0.25 (wherein α=1/10×Si+3/5×P+6×N), and the expression 3: β<0.7 (wherein β=C+0.18×Si+0.52×P). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３８】
【表２】

【００３９】
表１，表２において、比較鋼Ａは、Ｃの含有量が本発明の下限値である０．１５％よりも低い０．１３％であり、これに伴ってＣｅｑが本発明の下限値である０．６よりも低い０．４７９となっており、その結果として鋼の硬さが低く十分な強度が得られていない。
【００４０】
比較鋼Ｂは逆にＣの含有量が本発明の上限値である０．３５％よりも多い０．３８％であり、これに伴って熱間加工性を表す指数であるβの値が本発明の範囲よりも高い０．７０となっており、このため鍛造時に部分的に割れが発生している。
【００４１】
次に比較鋼Ｃは、Ｓｉの含有量が本発明の下限値である１．２％よりも低い１．０１％であり、このためフェライトの強化度を表す指数としてのαの値が本発明の下限値である０．２５よりも低い０．２１となっており、耐久比が低くなっている。
【００４２】
比較鋼Ｄは、逆にＳｉの含有量が本発明の上限値である２％よりも多い２．５０％となっており、このためβの値が本発明の上限である０．７よりも大きい０．８１となっており、結果として鍛造時に部分的な割れを発生させている。
【００４３】
比較鋼Ｅは、Ｍｎの含有量が本発明の上限値である１．５％よりも多い１．８０％であり、このため鍛造後の冷却でベイナイトが発生している。
【００４４】
比較鋼Ｆは、Ｐの含有量が本発明の下限値である０．０５％よりも低い０．０４０％であり、このためα値が０．２５と低く耐久比が低くなっている。
【００４５】
次に比較鋼Ｇは、Ｐの含有量が逆に本発明の上限値である０．２％よりも多い０．２１０％であり、これに伴ってβ値が０．７０と高く、鍛造時に部分的に割れが発生している。
【００４６】
比較鋼Ｈは、Ｃｒの含有量が本発明の上限値である１％よりも多い１．０１％であり、鍛造後の冷却でベイナイトが発生している。
【００４７】
比較鋼Ｉは、Ａｌの含有量が本発明の下限値である０．００１％よりも低い０．０００５％であり、そのため鍛造後結晶粒が粗大化し耐久比が低くなっている。
【００４８】
比較鋼Ｊは、Ｎの含有量が本発明の下限値である０．００５％よりも低い０．００１％であり、このためα値が０．２２と低く、耐久比が低くなっている。
【００４９】
比較鋼Ｋは、Ｃ〜Ｎの各合金成分のそれぞれの含有量は本発明の範囲内になっているものの、β値について見るとその値が本発明の上限値である０．７よりも大きい０．７４となっており、そのため鍛造時に部分的に割れを発生している。
【００５０】
比較鋼Ｌも同じく各合金成分の含有量はそれぞれ単独で規定している本発明の含有範囲内にあるものの、α値が本発明の下限値である０．２５よりも小さい０．２２であり、耐久比が低くなっている。
【００５１】
尚表１，表２中Ｓ４５Ｃの欄は一般的な機械構造用炭素鋼であるＳ４５Ｃを調質処理（焼入れ・焼戻し処理）をせずに、発明鋼１〜発明鋼９及び比較鋼Ａ〜比較鋼Ｌと同様に鍛造ままで使用したもので、この場合α値が０．０９と大幅に低く、耐久比の値も低いものとなっている。
【００５２】
これに対し本発明例の発明鋼１〜発明鋼９は硬さ，引張強さ，疲れ限度，耐久比等の諸特性が、Ｖ添加鋼であるＳ３５ＶＣと比較しても同等以上のものとなっている。
このことからも本発明によれば高性能なコンロッド用の熱間鍛造用非調質鋼を安価に提供できることが理解できる。
【００５３】
以上本発明の実施例を詳述したがこれはあくまで一例示であり、本発明はその趣旨を逸脱しない範囲において種々変更を加えた形態で構成可能である。
【図面の簡単な説明】
【図１】各合金元素の含有量変化と耐久比変化の関係を表す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a non-heat treated steel for hot forging used as a material for a connecting rod (connecting rod), specifically, without adding an expensive element V, and omitting a tempering treatment (quenching / tempering treatment). Also, the present invention relates to a non-heat treated steel for hot forging for a V-free connecting rod, which can provide a high strength and fatigue strength and can obtain a high-strength connecting rod at low cost.
[0002]
[Prior art]
Conventionally, connecting rods used as engine parts of automobiles have been manufactured by subjecting carbon steel for machine structure to hot forging and then tempering (quenching / tempering) to adjust the strength.
However, when the connecting rod is made of such a tempered steel, there is a problem that the required processing cost is increased due to the quenching / tempering process and the lead time is lengthened.
[0003]
Therefore, in recent years, for the purpose of cost reduction and shortening of the lead time, non-heat treated steel for hot forging, which can omit the tempering treatment, has been used as connecting rod steel.
That is, it is becoming common to form a connecting rod by using non-heat treated steel while hot forging.
[0004]
Conventionally, as such a non-heat treated steel for hot forging, V-added steel containing about 0.1% of V in carbon steel for machine structure or manganese steel for machine structure has been used as a typical one. I have.
This V-added non-heat treated steel for hot forging causes V carbonitride to be finely precipitated during cooling after hot forging, and develops the desired strength by precipitation hardening.
The main purpose of the V-added non-heat treated steel is to save cost by omitting the tempering treatment. However, V to be added is an expensive element, and the addition of such V increases the material cost. There was a problem that the cost merit due to the omission of the tempering treatment could not be fully utilized.
[0005]
On the other hand, when a connecting rod is formed by simply using carbon steel for machine structure or manganese steel for machine structure as hot forged, the strength, particularly the fatigue strength, is lower than that of the non-heat treated steel to which V is added.
[0006]
A non-heat treated steel for hot forging for solving this problem is disclosed in Patent Document 1 below.
The non-heat treated steel for hot forging disclosed in Patent Literature 1 is such that inexpensive P or Si is added instead of V to increase the fatigue strength.
[0007]
[Patent Document 1]
JP-A-9-310152 [0008]
[Problems to be solved by the invention]
However, the non-heat treated steel for hot forging disclosed in Patent Document 1 is applicable to a wide range of machine structural parts including not only engine parts of automobiles but also undercarriage parts, that is, for a wide range of purposes. One of the main objectives of the present invention is to minimize the toughness as much as possible.
Therefore, in the non-heat treated steel for hot forging disclosed in Patent Document 1, the P content is reduced in order to prevent a decrease in toughness (impact value) and a decrease in hot workability as shown in the examples. Is suppressed to 0.05% or less, and the Si content is suppressed to 1.2% or less.
[0009]
On the other hand, a connecting rod as an engine component to which the present invention is applied is not particularly required to have high toughness (impact value) required for a suspension component, and is a component requiring higher proof stress and fatigue strength. In addition, the non-heat-treated steel for hot forging disclosed in Patent Document 1 cannot sufficiently satisfy the demand.
[0010]
Here, the present invention provides a hot-forged hot-forged non-heat treated steel for connecting rods that can obtain a fatigue strength equivalent to that of a high-strength non-heat treated steel to which V is added without hot forging without adding V, which is an expensive element. The purpose of this is to provide at low cost.
[0011]
[Means for Solving the Problems]
The non-heat treated steel for hot forging according to claim 1 is, by weight%, C: 0.15 to less than 0.35%, Si: more than 1.2 to 2%, Mn: 0.5 to 1%. 0.5%, P: more than 0.05 to 0.2%, Cu: 0.01 to 0.5%, Ni: 0.01 to 0.5%, Cr: 0.01 to 1%, s-Al : 0.001 to 0.01%, N: 0.005 to 0.035% The balance consists of Fe and inevitable impurities and satisfies the following formulas 1, 2 and 3.
Formula 1 ... 0.6 ≦ Ceq ≦ 0.85
However, Ceq = C + 0.07 × Si + 0.16 × Mn + 0.61 × P + 0.19 × Cu + 0.17 × Ni + 0.2 × Cr
Expression 2 ... α> 0.25
Where α = 1/10 × Si + 3/5 × P + 6 × N
Equation 3 ... β <0.7
Where β = C + 0.18 × Si + 0.52 × P
[0012]
According to claim 2, in claim 1, S: ≤ 0.15%, Pb: ≤ 0.3%, Bi: ≤ 0.3%, Ti: ≤ 0.02%, Zr: ≤ 0.02. %, Ca: 0.0001 to 0.01%, and O: 0.001 to 0.01%.
[0013]
[Action and effect of the invention]
The non-heat-treated steel for hot forging according to the present invention is designed for connecting rods, and contains a large amount of Si, P, and N as elements for solid solution strengthening of ferrite, so that the starting point of fatigue fracture and In order to increase the strength of ferrites and to secure desired hot workability in spite of their addition, the upper limits of the contents of Si, P, and N were found and determined, and the required hardness was also adjusted. The main point is that the addition amounts of the respective alloy components including C are set within the appropriate addition amount ranges in order to ensure the above.
[0014]
Generally, when P is contained in a large amount, toughness (impact value) is reduced. Therefore, it is difficult to contain a large amount of P in a non-heat treated steel for hot forging, particularly for undercarriage parts requiring toughness.
However, the connecting rod as an engine component does not require such high toughness as described above, and can contain a large amount of P.
[0015]
FIG. 1 shows the relationship between the change in the alloy element content and the change in the durability ratio (fatigue limit / tensile strength).
This durability ratio is a value obtained by dividing the fatigue limit by the tensile strength, and a higher value means a higher fatigue strength at the same static strength.
As is clear from this figure, P and Si are elements that improve the durability ratio like V.
On the other hand, Pb and C lower the durability ratio.
The present invention is intended to reduce the C content and to obtain a high fatigue strength by containing a large amount of P and Si by focusing on this point.
[0016]
P and Si are elements that greatly lower the melting point together with C. If a large amount of P or Si is contained, these components are segregated during solidification during hot forging, resulting in a partially concentrated portion. .
Since the concentrated portion has a low melting point, the portion is melted during slab rolling or the like and causes cracking.
[0017]
Therefore, in the present invention, while increasing the content of Si and P, the content of C is adjusted, and more specifically, the content of C is regulated to a certain level or less to prevent a decrease in hot workability, and on the other hand, to reduce the C content. The required hardness is realized by adding other components and balancing the components while controlling the content to a certain level or less.
Further, a decrease in the content of C is also effective in improving the durability ratio.
The non-heat treated steel for hot forging according to the present invention makes it possible to manufacture a connecting rod as an engine component at a low cost without performing a tempering treatment. In addition, the connecting rod can be provided with necessary proof stress and fatigue strength. It becomes possible.
[0018]
In the present invention, one or two or more free-cutting components such as S, Pb, Bi, Ti, Zr, Ca, and O can be contained at a predetermined content as needed. 2).
[0019]
Next, the reason for adding and limiting each chemical component in the present invention will be described in detail below.
C: 0.15 to less than 0.35% C is an element necessary for securing the strength, and it is necessary to add 0.15% or more.
On the other hand, C lowers the durability ratio and the melting point of steel. In ordinary steel for machine structural use, even if C is added in an amount of 0.35% or more, the melting point of the steel is not lowered and the hot workability is not impaired. Is concentrated at the site where solidification and segregation occur during ingot formation, and a region having a very low melting point is partially generated.
Further, since C that lowers the melting point is also concentrated at this portion, such a solidified segregated portion is melted at the time of slab rolling to cause cracking.
Solidification segregation occurs even in ordinary steel, but the above-mentioned phenomenon does not occur unless P and Si are added in large amounts.
In addition, the durability ratio can be improved by reducing the C content.
In the present invention, the upper limit of the C content is set to 0.35% in order to suppress such a decrease in hot workability peculiar to steel having a high P and Si content and to prevent a decrease in the durability ratio due to the absence of V. I do.
[0020]
Si: more than 1.2 to 2%
Si has a deoxidizing effect at the time of smelting steel, and forms a solid solution in ferrite as an alternative element to V, and improves the strength of ferrite which is a soft phase by solid solution strengthening, thereby improving fatigue strength.
For this reason, it is preferable to add as much Si as possible in V-free steel. However, if too much Si is added, machinability and hot workability are reduced, so the range is set to more than 1.2% to 2%.
[0021]
Mn: 0.5-1.5%, Cr: 0.01-1%
Mn and Cr are elements that increase the strength of the forged material and also refine the pearlite lamella to improve proof stress and fatigue strength.
However, when a large amount is added, bainite is formed after forging, and the hardness is remarkably increased to reduce the machinability. Therefore, the respective ranges are Mn: 0.5 to 1.5% and Cr: 0.01 to 1%. And
[0022]
P: more than 0.05 to 0.2%
P is a component unavoidably contained, and generally can be suppressed as low as possible as an impurity element which lowers toughness due to segregation at grain boundaries.
However, P is an effective element that, like Si, strengthens ferrite by solid solution and greatly improves fatigue strength.
For parts that require high toughness, such as undercarriage parts for automobiles, it is difficult to increase the strength by adding a large amount of P, but not so high toughness like connecting rods, and higher fatigue strength. There is no problem even if it is positively added to parts that require.
[0023]
However, P is an element that significantly lowers the melting point of steel and degrades hot workability. When added in a large amount, P causes local melting at a solidification segregation portion during slab rolling to cause cracking.
Therefore, the range of the P content needs to be more than 0.05 to 0.2%.
[0024]
Cu: 0.01 to 0.5%, Ni: 0.01 to 0.5%
Cu and Ni are elements that increase the strength after forging, as well as Mn and Cr, refine the pearlite lamella, and improve proof stress and fatigue strength.
However, since Cu and Ni are more expensive elements than Mn and Cr, it is disadvantageous in cost to positively add a large amount.
Therefore, the added amount is set to Cu: 0.01 to 0.5% and Ni: 0.01 to 0.5%.
[0025]
s-Al: 0.001 to 0.01%
s-Al has a deoxidizing action when melting steel, generates fine nitrides, and improves strength by suppressing crystal grain coarsening during hot forging.
However, even if it is added in a large amount, its effect is saturated.
[0026]
N: 0.005 to 0.035%
N, like Si and P, is an element for solid solution strengthening of ferrite, and is effective in improving fatigue strength.
Further, a part of N contained therein forms fine nitrides with Al and is dispersed in the steel, thereby suppressing coarsening of crystal grains during hot forging.
However, if the N content is less than 0.005%, it is economically disadvantageous, and if a large amount is added, it causes casting defects. Therefore, the range is made 0.005 to 0.035%.
[0027]
Pb: ≦ 0.3%, Bi ≦ 0.3%
Since both Pb and Bi are effective elements for improving the machinability, when it is required that the machinability is further improved in the forged product, select from these as necessary. It is also possible to add an appropriate amount of one or two of these.
However, if the addition amount is too large, the strength and the hot workability are reduced. Therefore, even if they are added, Pb: ≦ 0.3% and Bi: ≦ 0.3%, respectively.
[0028]
S: ≦ 0.15%
S is an element effective for forming MnS and improving machinability. When improvement in machinability is required, S may be added in an appropriate amount as necessary.
However, if added in a large amount, the fatigue strength and hot workability are reduced, so the content is made 0.15% or less.
[0029]
Ca: 0.0001 to 0.01%
Ca partially substitutes for Mn in MnS to form MnS containing Ca.
Such MnS in which Ca is dissolved as a solid solution adheres to the tool during cutting, and suppresses tool wear and improves machinability.
To obtain such an effect, Ca must be added in an amount of 0.0001% or more.
However, even if it is added in a large amount, its effect is saturated, so that the content is made 0.01% or less.
[0030]
Ti: ≦ 0.02%, Zr ≦ 0.02%
Ti and Zr have an effect of miniaturizing the distribution state of MnS. The miniaturized MnS improves chip crushability during machining.
However, even if it is added excessively, the effect is saturated and it is economically disadvantageous. Therefore, Ti: ≦ 0.02% and Zr ≦ 0.02%, respectively.
It is preferable to add 0.0005% or more of each.
[0031]
O: 0.001 to 0.01%
In order to obtain MnS in which Ca is dissolved, it is necessary that an oxide of Ca exists adjacent to the MnS.
To obtain such effects, 0.001 to 0.01% of O is required.
[0032]
0.6 ≦ Ceq ≦ 0.85
However, Ceq = C + 0.07 × Si + 0.16 × Mn + 0.61 × P + 0.19 × Cu + 0.17 × Ni + 0.2 × Cr
Ceq is a value representing the hardness after forging of the non-heat treated steel, and by adjusting this value, the hardness after forging can be managed.
Hardness is a factor that affects proof stress, fatigue strength, and machinability. If the hardness is too low, the desired fatigue strength cannot be obtained. Conversely, if the hardness is too high, the machinability deteriorates. Is not preferred.
In order to prevent this from occurring, it is necessary to adjust the hardness to an appropriate range.
Therefore, the range of Ceq is set to 0.6 to 0.85.
[0033]
α> 0.25
Where α = 1/10 × Si + 3/5 × P + 6 × N
α is an index indicating the degree of strengthening of the ferrite, and the larger this value is, the more the fatigue strength is improved.
To obtain the same proof stress and fatigue strength as the V-added high-strength non-heat treated steel, α needs to be larger than 0.25.
[0034]
β <0.7
Where β = C + 0.18 × Si + 0.52 × P
β is an index indicating hot workability.
As described above, C, Si, and P are enriched in the solidified segregated portion generated during the ingot formation, and the melting point of the solidified segregated portion is significantly reduced.
For this reason, the solidified segregation portion may be locally melted at the time of slab rolling, and the hot workability may be significantly reduced.
In order to suppress such a phenomenon, it is necessary that β calculated from the C, Si, and P contents is less than 0.7, thereby increasing the amount of C, Si, and P enriched in the solidification segregation portion. And the hot workability can be maintained favorably.
[0035]
【Example】
After ingoting the steels of the present invention and the comparative steels shown in Table 1, the ingots were ingot, hot forged to form a 50 mm square forged material, which was heated and held at 1200 ° C. for 60 minutes, and then turned into a round bar having a diameter of 22 mm. Hot forging was carried out, left on the floor at appropriate intervals so as not to overlap, and allowed to cool to room temperature.
An Ono-type rotary bending fatigue test piece having a parallel part diameter of 8 mm and a JIS No. 4 tensile test piece (parallel part diameter φ8 mm, reduced size) were cut out from the round bar and subjected to a test.
Here, the hardness was determined by measuring the hardness of a 1 / 2R part of a forged 22 mm diameter round bar with a Rockwell hardness tester.
[0036]
The fatigue test and the tensile test were performed at room temperature. The results are shown in Table 2.
Table 2 also shows the durability ratio.
For comparison, Tables 1 and 2 also show test results of carbon steel S45C for mechanical structures and non-heat treated steel S35VC for connecting rods, which are generally used in Japan as conventional steels.
[0037]
[Table 1]

[0038]
[Table 2]

[0039]
In Tables 1 and 2, Comparative Steel A has a C content of 0.13%, which is lower than the lower limit of 0.15% of the present invention, and Ceq is accordingly lower than the lower limit of the present invention. The value is 0.479, which is lower than a certain 0.6, and as a result, the hardness of the steel is low and sufficient strength is not obtained.
[0040]
Conversely, the comparative steel B has a C content of 0.38%, which is more than the upper limit of 0.35% of the present invention, and accordingly, the value of β, which is an index representing hot workability, is reduced by the value of β. It is 0.70, which is higher than the range of the invention, and therefore, cracks are partially generated during forging.
[0041]
Next, in Comparative Steel C, the content of Si is 1.01%, which is lower than the lower limit of 1.2% of the present invention, that is, the value of α as an index indicating the degree of strengthening of ferrite is different from that of the present invention. Is 0.21 which is lower than the lower limit value of 0.25, that is, the durability ratio is low.
[0042]
On the contrary, the comparative steel D has a Si content of 2.50%, which is more than the upper limit of 2% of the present invention, and thus the value of β is larger than 0.7, which is the upper limit of the present invention. The value is as large as 0.81, and as a result, a partial crack is generated during forging.
[0043]
Comparative steel E has a Mn content of 1.80%, which is more than the upper limit of 1.5% of the present invention, and therefore, bainite is generated by cooling after forging.
[0044]
Comparative steel F has a P content of 0.040%, which is lower than the lower limit of 0.05% of the present invention, that is, 0.05%. Therefore, the α value is as low as 0.25, and the durability ratio is low.
[0045]
Next, the comparative steel G has a P content of 0.210%, which is higher than the upper limit of 0.2% of the present invention, and the β value is as high as 0.70. Cracks have occurred partially.
[0046]
The comparative steel H has a Cr content of 1.01%, which is more than the upper limit of 1% of the present invention, and bainite is generated by cooling after forging.
[0047]
In Comparative Steel I, the Al content was 0.0005%, which is lower than the lower limit of 0.001% of the present invention, and thus the crystal grains after forging became coarse and the durability ratio was low.
[0048]
Comparative steel J has an N content of 0.001%, which is lower than the lower limit of 0.005% of the present invention, and therefore has a low α value of 0.22 and a low durability ratio.
[0049]
In Comparative Steel K, although the content of each of the alloy components C to N is within the range of the present invention, the value of β is larger than the upper limit of 0.7 of the present invention in terms of β value. 0.74, so that cracks were partially generated during forging.
[0050]
In Comparative Steel L, the content of each alloy component is also within the content range of the present invention stipulated independently, but the α value is 0.22 which is smaller than the lower limit value of 0.25 of the present invention. , The durability ratio is low.
[0051]
In addition, the column of S45C in Tables 1 and 2 shows that invention steel 1 to invention steel 9 and comparison steel A to comparison steel S45C, which is a general carbon steel for machine structure, were not subjected to a tempering treatment (quenching / tempering treatment). It was used as forged, like steel L. In this case, the α value was significantly low at 0.09, and the value of the durability ratio was also low.
[0052]
On the other hand, invention steel 1 to invention steel 9 of the present invention have various properties such as hardness, tensile strength, fatigue limit, durability ratio and the like as compared with S35VC which is a V-added steel. ing.
From this, it can be understood that according to the present invention, a high-performance non-heat treated steel for hot forging for a connecting rod can be provided at low cost.
[0053]
Although the embodiment of the present invention has been described in detail, this is merely an example, and the present invention can be configured in variously modified forms without departing from the spirit thereof.
[Brief description of the drawings]
FIG. 1 is a diagram showing a relationship between a change in the content of each alloy element and a change in durability ratio.

Claims (2)

In weight percent,
C: 0.15 to less than 0.35% Si: more than 1.2 to 2%
Mn: 0.5-1.5%
P: more than 0.05 to 0.2%
Cu: 0.01-0.5%
Ni: 0.01 to 0.5%
Cr: 0.01-1%
s-Al: 0.001 to 0.01%
N: 0.005 to 0.035%
A non-heat treated steel for hot forging for connecting rods, the balance being Fe and the unavoidable impurities and satisfying the following formulas (1), (2) and (3).
Formula 1 ... 0.6 ≦ Ceq ≦ 0.85
However, Ceq = C + 0.07 × Si + 0.16 × Mn + 0.61 × P + 0.19 × Cu + 0.17 × Ni + 0.2 × Cr
Expression 2 ... α> 0.25
Where α = 1/10 × Si + 3/5 × P + 6 × N
Equation 3 ... β <0.7
Where β = C + 0.18 × Si + 0.52 × P In claim 1,
S: ≦ 0.15%
Pb: ≦ 0.3%
Bi: ≦ 0.3%
Ti: ≦ 0.02%
Zr: ≦ 0.02%
Ca: 0.0001 to 0.01%
O: 0.001 to 0.01%
Non-heat treated steel for hot forging for connecting rods, further comprising one or more of the following.

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