JPH07228947A - Alloy with high strength and low thermal expansion - Google Patents

Abstract

PURPOSE:To produce an alloy having high strength and reduced in thermal expansion by preparing an alloy having a specific composition in which respective contents of C, Ni, V, and Cr are specified. CONSTITUTION:An alloy, which has a composition consisting of, by weight, 0.1-0.4% C, 0.2-1.5% Si, 0.1-1.5% Mn, 33-42% Ni, <=5.0% Co, 0.75-3.0% Cr, 0.2-3.0% V, <=0.003% B, <=0.003% O, <=0.1% Al, <=0.1% Mg, <=0.1% Ti, <=0.1% Ca, and the balance Fe with inevitable impurities and satisfying 1.0%<=V+Cr<=5.0%, is prepared. By this method, the alloy combining high strength with low thermal expansion, in which average thermal expansion coefficient at a temp. between room temp. and 300 deg.C and average thermal expansion coefficient at a temp. between room temp. and 100 deg.C are regulated to <=about 5.0X10<-6>/ deg.C and <=about 1.5X10<-6>/ deg.C, respectively, and which has >=about 1200N/mm<2> tensile strength at an ordinary temp., can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength and low-thermal expansion alloy used for precision machine parts which may increase in temperature during use, low sag heat resistant transmission lines, and the like.

[0002]

2. Description of the Related Art Invar alloy (36Ni-Fe) is often used as a material required to have heat resistance and low thermal expansion characteristics. This alloy has a relatively low magnetic transformation point of about 165 ° C. At temperatures above this temperature, the coefficient of thermal expansion tends to increase rapidly, the usable temperature range is narrow, and the tensile strength at room temperature is at most 600N. / mm ^2, which is unsatisfactory depending on the application.

There are alloys to which Nb, Ti, W, etc. are added in order to increase the tensile strength at room temperature. However, in these alloys, giant carbides are likely to precipitate and precipitate, in which case the toughness and the twist value after cold working are increased. Bring about a decline.

Alloys containing Mo have been developed for the purpose of strengthening the matrix (for example, Japanese Patent Publication No. 56-459).
However, although this alloy has a high tensile strength at room temperature, it also has a high coefficient of thermal expansion. For this reason, development of alloys with high strength and low thermal expansion is further desired.

[0005]

In order to increase the transmission capacity of overhead power transmission lines, various studies have been conventionally made to improve heat resistance to withstand use at high temperatures and reduce sag. In recent years, for example, an overhead power transmission line has been put into practical use for the purpose of reducing the sag, by applying tension to the steel core only, and then allowing only the steel core to undergo thermal expansion when the temperature rises due to energization after the overhead wire. Has been done. For this application, alloys with low expansion and high strength are desirable.

The present invention is intended to provide an optimum material for applications such as the above-mentioned core wire for power transmission lines and precision machine parts that may be heated during use, and the average temperature from room temperature to 300 ° C. Coefficient of thermal expansion is 5.0 × 10 ^-6 / ℃ or less, and room temperature to 100
Provided is a low thermal expansion alloy having an average thermal expansion coefficient of 1.5 × 10 ⁻⁶ / ° C. or less and room temperature tensile strength of 1200 N / mm ² or more.

[0007]

The high-strength low-thermal expansion alloy of the present invention which achieves the above-mentioned object is C: 0.1 in terms of weight ratio.
~ 0.4%, Si: 0.2-1.5%, Mn: 0.1-1.5%, Ni:
33 to 42%, Co: 5.0% or less, Cr: 0.75 to 3.0%, V: 0.2
~ 3.0%, B: 0.003% or less, O: 0.003% or less, Al:
0.1% or less, Mg: 0.1% or less, Ti: 0.1% or less, Ca: 0.
It is characterized by containing 1% or less, the balance being Fe and inevitable impurities, and having a relationship of 1.0% ≤V + Cr≤5.0%.

[0008]

The reason for defining the composition of the alloy of the present invention as described above is as follows. C is an element that greatly contributes to strengthening the material by solid solution hardening, and has a normal temperature tensile strength of 1000 N / mm ²
In order to secure the above, it is necessary to contain an amount of 0.1% or more. However, if it is contained in a large amount, carbides are easily formed and the original thermal expansion characteristics of the Fe-Ni alloy become unstable, so the content is limited to 0.4% or less. Therefore C: 0.1% to 0.4%
And

Si is a desirable element for lowering the coefficient of thermal expansion at low temperatures and hardening the matrix. However, excessive addition increases the coefficient of thermal expansion on the high temperature side, so 1.5
% Or less, preferably 1.0% or less, while less than 0.2% has no effect of hardening the matrix. Therefore, Si: 0.2% to 1.5%.

Mn is an element effective as a deoxidizing agent and, for this reason, 0.1% or more is necessary. However, if added in excess of 1.5% or more, the coefficient of thermal expansion increases, so it is desirable to keep it below 1.5%. Therefore, Mn: 0.1% to 1.5%.

Ni is an element indispensable for realizing low thermal expansion characteristics and has an average coefficient of thermal expansion of 5.0 × 10 ⁻⁶ at room temperature to 300 ° C.
/ ° C or less, and the average coefficient of thermal expansion from room temperature to 100 ° C
In order to secure 1.5 × 10 ^-6 / ° C or less, it is necessary to contain 33% or more. However, if its content exceeds 42%, the average coefficient of thermal expansion at room temperature to 300 ° C will be 5.0 × 10 ^-6.
It is difficult to secure the average thermal expansion coefficient of 1.5 × 10 ⁻⁶ / ° C. or less at room temperature to 100 ° C.
Therefore, Ni: 33% to 42%.

Co is often contained in ferro-nickel or Ni ingots as an unavoidable impurity in an amount of 0.1% or more, but the effect is the same as that of Ni, and the inclusion of Co is acceptable to some extent. However, it is more expensive than Ni, and if it exceeds 5.0%, it will raise the cost, so it should be 5.0% or less.

[0013] Cr has a large effect of strengthening the Fe-Ni alloy, and if it is less than 0.75%, it has no strengthening effect, and if it exceeds 3.0%, it cannot satisfy the thermal expansion characteristics, and it forms a strong oxide by heat treatment. Reduce the pretreatment of plating and lubricity during wire drawing. Therefore, Cr: 0.75% to 3.0%.

V has a large effect of strengthening the Fe-Ni alloy and an effect of refining carbides, and the effect is larger than that of Mo. In the present invention, V is added as a strengthening element in place of conventional Mo. V is also very effective in reducing the coefficient of thermal expansion. If it is less than 0.2%, there is no strengthening effect, and if it exceeds 3.0%, the effect is saturated and the cost is raised.
Therefore, V: 0.2% to 3.0%.

Here, the total amount of V and Cr is optimally 1.0 to 5.0%. If it is less than 1.0%, the desired mechanical strength cannot be obtained, and if it exceeds 5.0%, the thermal expansion characteristics are not satisfied. Therefore
1.0% ≤ V + Cr ≤ 5.0%.

B is an important element for improving hot workability, and exerts an effect regardless of hot working temperature conditions. If it exceeds 0.003%, Fe ₂ B is generated to cause red heat embrittlement. Therefore, B: 0.003% or less.

The value of O is 0.003% or less in order to reduce the oxide inclusions as much as possible, since the twist value after cold working is greatly reduced by the presence of the oxide inclusions.

Each element of Al, Mg, Ti and Ca may be added as a deoxidizing element together with Mn. In that case, 0.1% is added.
If it is contained in excess of, the characteristics will be adversely affected. Therefore Al,
Each element of Mg, Ti and Ca: 0.1% or less.

[0019]

[Examples] Next, the characteristics of the steel of the present invention will be clarified by examples compared with the conventional steel and the comparative steel. The alloy of the present invention consisting of the elements shown in Table 1 and ordinary impurities was melted and the diameter was 30 mm.
After forging, cold drawing was performed at 50% and annealing was performed at 700 ° C. Comparative steel was also manufactured by the same method. Tensile test pieces and thermal expansion test pieces were sampled from this material and subjected to the test. The tensile test is performed at room temperature, and the coefficient of thermal expansion is from room temperature to 100.
The measurement was performed between ℃ and normal temperature to 300 ℃. The results of these tests are also shown in Table 1.

[0020]

[Table 1]

In Table 1, the comparative steels No. 7, No. 8 and No. 9
C content is outside the specified value of the present invention, No. 10, No. 11, No. 1
2 is Ni, No. 13 is Cr and V, No. 14 and No. 15 is V + Cr,
No. 16 is Al, No. 17 is Mg, No. 18 is Ti, No. 19 is Ca outside the specified value, No. 20 does not contain B at all, No. 20 is
O is outside the specified value.

Table 1 shows the influence of the content of each element.

Regarding the effect of C: As the amount of C increases, both the tensile strength and the coefficient of thermal expansion increase. In order to secure a tensile strength of 1200 N / mm ² , 0.1% or more of C is necessary.
That is, Comparative Steel No. 7 has a carbon content of 0.08%, which is lower than the specified value, and therefore the tensile strength is low, 831 N / mm ² . On the other hand, when a large amount of C is contained, the coefficient of thermal expansion becomes high, and it becomes difficult to secure 1.5 × 10 ⁻⁶ / ° C. as seen in Comparative Steel Nos. 8 and 9. Therefore, it can be seen that 0.40% or less is desirable.

Regarding the effect of Ni: When Ni is 36%,
It has the lowest coefficient of thermal expansion. In order to secure the average coefficient of thermal expansion at room temperature to 100 ℃ below 1.5 × 10 ^-6 / ℃,
The Ni content must be 33% ≤ Ni ≤ 42%.

Regarding the effect of V + Cr: As V + Cr increases, the tensile strength also increases. But V + Cr is 1.0
Less than% is not enough. The coefficient of thermal expansion is 5 for V + Cr.
If it exceeds%, the value will suddenly increase and the twist value will decrease, so V
+ Cr is preferably 1.0% ≤ V + Cr ≤ 5.0%.

[0026]

As described above, the present invention can be performed at room temperature to 300 ° C.
Has an average coefficient of thermal expansion of 5.0 × 10 ^-6 / ° C or less, and an average coefficient of thermal expansion of room temperature to 100 ° C of 1.5 × 10 ^-6 / ° C or less, and a high room temperature tensile strength of 1200 N / mm ^2. It is a high-strength, low-thermal-expansion alloy that is not found in conventional alloys and has high strength and low-thermal expansion used for precision machinery parts that may heat up during use, low-sag heat-resistant transmission lines, etc. It is an extremely excellent alloy.

Claims (1)

[Claims] 1. A weight ratio of C: 0.1 to 0.4%, Si:
0.2 to 1.5%, Mn: 0.1 to 1.5%, Ni: 33 to 42%, Co:
5.0% or less, Cr: 0.75 to 3.0%, V: 0.2 to 3.0%, B:
0.003% or less, O: 0.003% or less, Al: 0.1% or less, M
g: 0.1% or less, Ti: 0.1% or less, Ca: 0.1% or less, the balance being Fe and inevitable impurities, and
A high-strength, low-thermal expansion alloy having a relationship of 1.0% ≤ V + Cr ≤ 5.0%.