JPH0873982A - High toughness ausforging steel - Google Patents

Abstract

PURPOSE: To produce a high toughness ausforging steel minimal in the dispersion of toughness. CONSTITUTION: This steel has a composition consisting of, by weight, 0.02-0.15% C, 0.1-1.0% Si, 0.5-3.0% Mn, 0.1-0.5% Cr, 0.0005-0.0050% B, 0.01-0.05% Ti, 0.01-0.05% Al, <=0.020% N, <=0.0050% O, and the balance Fe with impurities and containing, if necessary, one or >=2 kinds selected from <=0.50% Mo, <=1.00% Ni, =0.05% Nb, and =0.30% V and also containing, if necessary, one or >=2 kinds selected from >=0.20% S, <=0.25% Pb, <=0.30% Te, <=0.01% Ca, and <=0.30% Bi.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to parts manufactured by forging, such as knuckle arms, knuckle spindles,
The present invention relates to a high toughness forging and quenching steel that is used as a material for connecting rods and has excellent machinability.

[0002]

2. Description of the Related Art Conventionally, when the above-exemplified components are manufactured by forging, a heat treatment such as quenching and tempering is often performed after forging. Heating for austenitization, 2. Cooling from austenite,
3. It is usual to take steps such as tempering after quenching.

However, when performing such heat treatment (tempering treatment), a heat treatment furnace for reheating the forged product, a quenching tank for cooling and a tempering furnace for tempering are required. Therefore, the man-hours and equipment cost increase, and the work time also increases.

Therefore, in order to save energy and shorten the working time, V (vanadium) is also added to the material so that high toughness can be obtained without performing the above-mentioned tempering treatment, and air cooling is performed after hot forging. In some cases, VC was precipitated by cooling with blast cooling to obtain high strength in a non-heat treated state.

[0005]

However, the V-added non-heat treated steel containing V can obtain high strength in a non-heat treated state after hot forging, but it cannot obtain high toughness. There was a problem that it was difficult to obtain a forged product with stable quality because the toughness was likely to vary.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional problems, and is forged and fired by using a steel in which C, Mn, Cr, etc. are adjusted so that a required hardness can be obtained as quenched. It is possible to drastically improve the toughness as compared with the conventional V-added non-heat treated steel by introducing a martensite or bainite structure, and a high toughness forging with comparatively little variation in toughness. The purpose is to provide the required steel.

[0007]

Configuration of the Invention

The high toughness forging and quenching steel according to the present invention has a weight ratio of C: 0.02 to 0.15.
%, Si: 0.1 to 1.0%, Mn: 0.5 to 3.0
%, Cr: 0.1 to 0.5%, B: 0.0005 to 0.
0050%, Ti: 0.01 to 0.05%, Al: 0.
01-0.05%, N: 0.020% or less, O: 0.0
Including 050% or less, Mo: 0.50% or less, Ni: 1.00% or less, Nb: 0.05% or less, as required.
V: Includes one or more selected from 0.30% or less, and, if necessary, S: 0.20% or less,
Pb: 0.25% or less, Te: 0.30% or less, Ca:
0.01% or less, Bi: 0.30% or less, one or two or more selected, and the balance Fe and impurities, characterized in that the structure of the present invention described above. It is a means to solve it.

Next, the reasons for limiting the component range (weight basis) of the high toughness forging and quenching steel according to the present invention will be explained. C: 0.02 to 0.15% C is an element effective in securing the strength and toughness of the forged product, and it is necessary to contain 0.02% or more to obtain such an effect. ． However, if it is too large, the toughness decreases, so 0.15% or less is necessary. Also, considering the balance between strength and toughness, 0.06% or less is desirable.

Si: 0.1 to 1.0% Si has a deoxidizing action and a desulfurizing action during steel melting, and controls the form of inclusions to improve the forge hardenability and forging. It is an effective element for enhancing and adjusting the strength and toughness of the product, and it is necessary to contain 0.1% or more to obtain such effects. However,
If the content is too large, the workability deteriorates and the ductility decreases, so it is necessary to set it to 1.0% or less.

Cr: 0.1 to 0.5% Cr is an effective element for improving the hardenability and enhancing or adjusting the strength and toughness of the forged product, and in order to obtain such an effect. Must contain 0.1% or more. However, if the amount is too large, the strength becomes too large and the toughness and workability deteriorate, so it is necessary to set it to 0.5% or less.

B: 0.0005 to 0.0050% B is an element effective in improving the hardenability during forging and quenching and ensuring the core strength of the forged product. In order to obtain it, it is necessary to contain 0.0005% or more. However, even if B is added excessively, the improvement in hardenability is saturated, so the content was made 0.0050% or less.

Ti: 0.01-0.05% Ti is an element effective for fixing N in order to make the effect of adding B sufficient, and 0.01 to obtain such an effect. It is necessary to make it more than%. But T
Even if i is added excessively, the effect will be saturated, so 0.05
% Or less.

Al: 0.01 to 0.05% Al is an element having a strong deoxidizing action during the melting of steel, and is an element effective for refining crystal grains to improve strength and toughness. Therefore, in order to obtain such an effect, it is set to 0.01% or more. However, even if added excessively, the effect of grain refinement is saturated, so the content was made 0.05% or less.

N: 0.020% or less If a large amount of N is present in the steel, it reacts with B to form BN, and B
The effect of improving the hardenability cannot be sufficiently obtained by the addition. Therefore, it should be 0.020% or less.

O: 0.0050% or less 0 is generally present as an unavoidable impurity in steel, and if it is present in a large amount, it decreases toughness, so it must be 0.0050% or less.

Mo: 0.50% or less, Ni: 1.00%
Hereinafter, one or more selected from Nb: 0.05% or less and V: 0.30% or less Mo, Ni, Nb, and V are all effective for improving the strength and toughness of the forged product. Since it is a simple element, one or more of these elements may be added as necessary.

Mo is an element useful for adjusting the strength and toughness of the forged product, but if it is too much, the workability deteriorates, so even if it is contained, it should be 0.5% or less.

Ni is an element useful for improving toughness,
If it is contained too much, the workability will be deteriorated, so even if it is contained, it should be 1.00% or less.

Nb is an element useful for refining the crystal grains and improving the toughness, but even if added in a large amount, the effect is saturated, so even if it is contained, it must be 0.05% or less. is there.

V is an element useful for adjusting the strength of the forged product, but if it is too much, it deteriorates the workability, so if it is contained, it must be 0.3% or less.

S: 0.20% or less, Pb: 0.25% or less, Te: 0.30% or less, Ca: 0.01% or less, B
i: One or two or more selected from 0.30% or less S, Pb, Te, Ca, Bi are all effective elements for improving machinability, so that they are machined in a forged product. When it is required that the properties be further improved, it is advisable to add an appropriate amount of one or more selected from these, if necessary.

However, if the addition amount is too large, the hot workability is deteriorated or the toughness is deteriorated. Therefore, even if added, S is 0.20% or less and Pb is 0.25%.
Below, Te is 0.30% or less, Ca is 0.01% or less,
Bi must be 0.30% or less.

[0023]

The high strength forging and quenching steel according to the present invention comprises:
Since the forging and quenching steel is hot forged into a desired shape because it has the above-mentioned structure, the residual heat from the hot forging is used, and the temperature is appropriately lowered as necessary. The Ar3 transformation point or higher (eg, Ar3 + 50 ° C)
By quenching from the temperature of
Forged products with excellent toughness can be obtained, and forged products with excellent toughness can be obtained without tempering without necessarily performing tempering thereafter.

[0024]

EXAMPLES Steels of the present invention shown in Table 1 (Nos. 1-5, 7-
9, 11, 15 to 25) and comparative steel (No. 6, 1)
0, 12 to 14) were melted and then ingot, hot forged to a forging material with a diameter of 90 mm, and 12 for each forging material.
After heating and holding at 00 ° C for 30 minutes, hot forging was performed to obtain a round bar material having a diameter of 40 mm, which was rapidly cooled by water cooling from a temperature of 900 ° C or higher, which is baked after hot forging. Next, the hardness and impact value tool life of each forged product were measured.

Among these, the hardness indicates the result of measuring the hardness of the center of each forged product with a Rockwell hardness tester, and the impact value was 2 after cutting out a JIS No. 3 Charpy impact test piece.
The results of Charpy impact test performed at 5 ° C are shown. The tool life is the result of drill test under the conditions shown in Table 2. These results are also the first
Shown in the table.

In addition, a conventional steel (No. 26), which is also composed of ordinary non-heat treated steel components shown in Table 1, is melted, ingoted and hot forged to a diameter of 90 mm, and then 1200
After heating and holding at ℃, hot forging to a diameter of 40 mm and then allowed to cool, the hardness, impact value and tool life of each forged product were measured in the same manner as above. The results are also shown in Table 1.

Further, the conventional steel (No. 27), which is also composed of the usual non-heat treated steel components shown in Table 1, is melted, ingoted and hot forged to a diameter of 90 mm, and subsequently a diameter of 40 m.
After forging to m, it was held at 1000 ° C. for 1 hour for oil cooling, then tempered, and the hardness, impact value and tool life of each forged product were measured in the same manner as above. These results are also shown in Table 1.

Table 1

Table 2

As is clear from Table 1, the steel of the present invention (N
o. 1-5,7-9,11,15-25), compared with the comparative steel (No.6,10,12-14), the impact value of the central portion is large in the non-heat treated state. It has high toughness up to the center. In addition, forging and quenching

[0032] It was found that the impact value is significantly improved and the toughness can be improved by simply rubbing compared with the conventional V-added non-heat treated steel (No. 26) and the case of quenching and tempering (No. 27). ．

[0033]

As described above, the high toughness forging and quenching steel according to the present invention has a weight ratio of C: 0.02 to 0.02.
0.15%, Si: 0.1-1.0%, Mn: 0.5-
3.0%, Cr: 0.1 to 0.5%, B: 0.0005
To 0.0050%, Ti: 0.01 to 0.05%, A
1: 0.01 to 0.05%, N: 0.020% or less,
O: including 0.0050% or less,

If necessary, Mo: 0.50% or less, N
i: 1.00% or less, Nb: 0.05% or less, V: 0.
One or more selected from 30% or less, and if necessary, S: 0.20% or less, Pb:
0.25% or less, Te: 0.30% or less, Ca: 0.0
1% or less, Bi: 0.30% or less selected 1
Including species or two or more species,

Since the balance is composed of Fe and impurities, it is not necessary to perform heat treatment after forging.
Since the residual heat from forging can be used for heating during quenching, reheating to the quenching temperature can be omitted in a separate process after forging, and the tempering process after quenching can be omitted. Since the forged product has a good impact value and can be made to have excellent toughness even at the center of the forged product, it is possible to obtain the toughness variation as in the conventional V-added steel and It has a remarkably excellent effect in that it does not easily cause a decrease in toughness.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical indication C22C 38/60

Claims (4)

[Claims] 1. C: 0.02-0.15% Si: 0.1-1.0% Mn: 0.5-3.0% Cr: 0.1-0.5% B: by weight 0.0005 to 0.0050% Ti: 0.01 to 0.05% Al: 0.01 to 0.05% N: 0.020% or less 0: 0.0050% or less The balance is Fe and impurities. Characteristically high toughness forging steel. 2. C: 0.02-0.15% Si: 0.1-1.0% Mn: 0.5-3.0% Cr: 0.1-0.5% B: by weight 0.0005 to 0.0050% Ti: 0.01 to 0.05% Al: 0.01 to 0.05% N: 0.020% or less O: 0.0050% or less and Mo: 0.50% or less Ni: 1.00% or less, Nb: 0.05% or less, V: 0.30% or less, and one or more selected from the balance F
High toughness forging steel characterized by comprising e and impurities. 3. C: 0.02-0.15% Si: 0.1-1.0% Mn: 0.5-3.0% Cr: 0.1-0.5% B: by weight 0.0005 to 0.0050% Ti: 0.01 to 0.05% Al: 0.01 to 0.05% N: 0.020% or less O: 0.0050% or less and S: 0.20% or less Pb: not more than 0.25% Te: not more than 0.30% Ca: not more than 0.01% Bi: not more than 0.30%, including one or more selected from the rest F
High toughness forging steel with excellent machinability, which is characterized by comprising e and impurities. 4. C: 0.02-0.15% Si: 0.1-1.0% Mn: 0.5-3.0% Cr: 0.1-0.5% B: by weight 0.0005 to 0.0050% Ti: 0.01 to 0.05% Al: 0.01 to 0.05% N: 0.020% or less O: 0.0050% or less and Mo: 0.50% or less Ni: 1.00% or less Nb: 0.05% or less V: 0.30% or less One or two or more selected from S: 0.20% or less Pb: 0.25% or less Te: 0 30% or less Ca: 0.01% or less Bi: 0.30% or less One or more selected from, balance F
High toughness forging steel characterized by comprising e and impurities.