KR20080063137A - High speed cold working steel and its manufacturing method, and high speed cold working parts and its manufacturing method - Google Patents

Abstract

An object of the present invention is to provide a steel for high speed cold working which is excellent in cold workability during processing and exhibits good hardness after processing.

C: 0.03% to 0.6% (meaning of mass%, the same below), Si: 0.005% to 0.6%, Mn: 0.05 to 2%, P: 0.05% or less (not including 0%), S: 0.05% For high speed cold working containing no more than 0%, and N: 0.04% or less (not including 0%), the remainder being made of iron and unavoidable impurities, and the amount of solid nitrogen in steel being 0.006% or more It is a river.

Description

STEEL FOR HIGH-SPEED COLD WORKING AND METHOD FOR PRODUCTION THEREOF, AND PART FORMED BY HIGH-SPEED COLD WORKING AND METHOD FOR PRODUCTION THEREOF}

The present invention relates to cold working steels, in particular cold wires or bars, which are useful for producing mechanical parts such as bolts and nuts, in particular automotive parts. The present invention also provides a cold worked part obtained from the cold work steel.

In recent years, from the viewpoint of environmental protection, there is a growing demand for weight reduction of parts intended to improve fuel efficiency of vehicles such as automobiles. The general high strength component ensures the strength as a component by increasing the amount of alloying elements added to iron.

Cold work (processing in an atmosphere of 200 ° C. or less here) has advantages such as high productivity, good dimensional accuracy, and good yield of steel as compared to hot work or warm work, and thus the manufacture of various parts. Widely used. In addition, there is a trend of high speed machining in order to further improve productivity.

Under such a background, the steel used for cold working needs to have low deformation resistance at the time of cold working, and it is necessary that the deformation performance does not fall during processing. If the deformation resistance of the steel is high, the life of the die used for cold working is reduced, while if the deformation ability is low, cracking is likely to occur during cold working.

It is known that what is necessary is just to reduce additional elements, such as C, Si, Mn, in order to reduce the deformation resistance of steel and to improve deformation capability. However, if the additional element is simply reduced and the deformation resistance is reduced, the life of the mold can be improved. However, a problem arises in that the necessary component strength cannot be obtained after processing. Therefore, in the past, after cold working steel into a predetermined shape, heat treatment such as quenching and tempering has been performed to secure a predetermined part strength (hardness).

However, if the heat treatment is performed after the machining of the component, the dimensions of the component are changed. Therefore, machining of the component such as cutting must be performed again from that time. In order to improve productivity and save energy, there is a demand for a solution capable of securing a predetermined component strength and eliminating heat treatment and subsequent processing.

Under such a background, Japanese Patent No. 3351979 discloses depositing fine nitrides in ferrite particles, and using them as nuclei to precipitate C compounds such as cementite in order to suppress the increase in deformation resistance during processing. .

Japanese Patent Laid-Open No. 60-82618 controls the amount of N and solid solution Al to fix N as AlN, and precipitates C as a C compound by aging treatment, thereby suppressing aging hardening by solid solution C and solid solution N. It discloses what can be done.

In the methods of the above-described patents Nos. 3535979 and JP-A-60-82618, in order to suppress dynamic distortion aging and suppress an increase in deformation resistance, solid solution N and solid solution C are added to N compounds and C in ferrite particles. It is immobilized as a compound. In order to fix solid solution N, it is necessary to add Al which is an N compound formation element. As in Example, if Al is 0.039 to 0.045%, even if the amount of N is 0.015%, it can be considered that there is almost no solid solution N. Moreover, since N compound has the effect of suppressing precipitation strengthening and grain coarsening, it is also conceivable to increase the deformation resistance by factors other than dynamic distortion aging.

Japanese Unexamined Patent Publication No. 57-60416 discloses a method for reducing strain resistance during cold working by adding Cr having a solid solution softening action and immobilizing solid solution N by adding Al. However, in the above method, since the solid solution N is immobilized as the N compound by adding Al, it is conceivable that the solid solution N hardly exists, as in Japanese Patent Nos. 35,959,23 and JP-A-60-82618. In addition, similar to Japanese Patent Nos. 3351979 and Japanese Patent Laid-Open No. 60-82618, since the N compound has an effect of inhibiting precipitation strengthening and grain coarsening, the deformation resistance is increased by factors other than dynamic distortion aging. I can think of it.

The hardened heat treatment, for example, quenching tempering, may be performed on the cold worked component after cold working in order to secure a predetermined component strength. However, as described above, in view of productivity improvement and energy saving, the heat treatment of quenching tempering is omitted. It is required to do it.

For example, in Japanese Unexamined Patent Publication No. 2003-266144, the aging hardening treatment (quenching tempering) after cold working can be omitted by cooling at a cooling rate of 50 to 70 ° C./hour from the exothermic temperature after cold working to room temperature. A method is disclosed.

Cold workability (strain resistance and deformability) and component strength after cold working are opposite properties. Securing the predetermined part strength deteriorates the mold life and easily cracks during processing. On the other hand, if the cold workability is improved to improve the mold life, it becomes impossible to secure a predetermined component strength. Conventionally, non-coarse cold working steels having both excellent characteristics have not been obtained. It is therefore an object of the present invention to provide a cold work steel, particularly a cold working wire rod or a bar, which exhibits good part strength after machining while excellent in cold workability during machining.

The steel for high speed cold working which is a basic aspect of this invention which could achieve the said objective,

C: 0.03% to 0.6% (mean of mass%, the same below),

Si: 0.005 to 0.6%,

Mn: 0.05 to 2%,

P: 0.05% or less (not including 0%),

S: 0.05% or less (not including 0%),

N: 0.04% or less (does not contain 0%),

The remainder is composed of iron and unavoidable impurities, and the amount of solid nitrogen in steel is 0.006% or more.

The C content of the high speed cold working steel of the present invention is further limited to 0.03 to 0.15% (first embodiment of the present invention) or more than 0.15 to 0.6% (second embodiment of the present invention), depending on the use and required performance. You may also

In the basic aspect, 1st, and 2nd aspect of this invention, in order to ensure 0.006% or more of solid solution N, it is preferable to set it as N: 0.007% or more.

In the basic aspect of this invention, 1st, and 2nd embodiment, it is also effective to contain Al: 0.1% or less (not containing 0%) besides the said component as needed.

In the basic aspects of the present invention, the first and second embodiments, in addition to the components described above, Zr: 0.2% or less (not including 0%) and Ti: 0.1% or less (not including 0%) as necessary. Nb: 0.1% or less (does not contain 0%), V: 0.5% or less (does not contain 0%), Ta: 0.1% or less (does not contain 0%), and Hf: 0.1% or less ( It is also effective to contain at least one selected from the group consisting of 0%).

In the basic aspects of the present invention, the first and second embodiments, in addition to the above components, B: 0.0015% or less (not including 0%) and / or Cr: 2% or less (including 0%) as necessary. It is also effective to contain at least one selected from the group consisting of

Under the present circumstances, it is recommended that each said component satisfy | fills following formula (1).

[N]-(14 [Al] / 27 + 14 [Ti] /47.9 + 14 [Nb] /92.9 + 14 [V] /50.9 + 14 [Zr] /91.2 + 14 [B] /10.8 + 14 [Ta ] /180.9 + 14 [Hf] /178.5) ≥ 0.006 ‥‥ (1)

[In formula (1), [] shows the total content (mass%) in the steel of each element.]

In addition, the content of the inevitable impurities is

Al: 0.001% or less (including 0%),

Ti: 0.002% or less (including 0%),

Nb: 0.001% or less (including 0%),

V: 0.001% or less (including 0%),

Zr: 0.001% or less (including 0%),

B: 0.0001% or less (including 0%),

Ta: 0.0001% or less (including 0%),

It is also one of the preferable embodiments to satisfy Hf: 0.0001% or less (including 0%) and satisfy the following formula (2) (third embodiment of the present invention).

14 [Al] / 27 + 14 [Ti] /47.9 + 14 [Nb] /92.9 + 14 [V] /50.9 + 14 [Zr] /91.2 + 14 [B] /10.8 + 14 [Ta] /180.9 + 14 [Hf] /178.5 ≤ 0.002% ‥‥ (2)

[In formula (2), [] shows the total content (mass%) in the steel of each element.]

It is preferable that the steel for high speed cold working of the 3rd Embodiment of this invention contains Cr: 2% or less (not containing 0%) further.

In addition to the above components, it is also effective to contain Cu: 5% or less (not including 0%) in the steel for high speed cold working of the present invention as needed.

The steel for high speed cold working of this invention contains Ni: 5% or less (not containing 0%) and / or Co: 5% or less (not containing 0%) besides the said component as needed. It is also valid.

In addition to the above components, the steel for high-speed cold working of the present invention may further contain Mo: 2% or less (not containing 0%) and / or W: 2% or less (not containing 0%) as necessary. It is also valid.

In addition to the above components, Ca: 0.05% or less (not including 0%) and rare earth elements (hereinafter, abbreviated as "REM"): 0.05% or less (0) in the high speed cold working steel of the present invention, if necessary. %), Mg: 0.02% or less (does not contain 0%), Li: 0.02% or less (does not contain 0%), Pb: 0.1% or less (does not contain 0%), and It is also effective to contain at least one selected from the group consisting of Bi: 0.1% or less (not containing 0%).

It is recommended to use the steel for high speed cold working of this invention for high speed cold working on the conditions of working temperature 200 degrees C or less. In addition, it is recommended to use for high speed cold working on the condition whose distortion rate is 100 / s or more.

The distortion rate is obtained by dividing true strain by unit time.

A method for producing high-speed cold working Steels of the present invention, heating a steel material having a composition the ingredients to a temperature Ac ₃ point + 30 ℃ or more, and then the hot working in the temperature range above Ac ₃ point + 30 ℃, and then 0.5 ℃ The method of cooling to 500 degrees C or less at the cooling rate of / s or more is recommended as a preferable aspect.

A method for producing high-speed cold working Steels of the present invention, heating a steel material having a composition the ingredients to a temperature Ac ₃ point + 30 ℃ or more, and then a method for cooling to below 500 ℃ in over 0.5 ℃ / s cooling rate is preferred Recommended as the sun.

The high speed cold working part of this invention is a high speed cold working part manufactured by high speed cold working the above-mentioned high speed cold working steel at the processing temperature of 200 degrees C or less and distortion rate 100 / s or more, and the component strength (H) after high speed cold working, And it is preferable that the maximum value DR of the deformation resistance during the high speed cold working satisfies the following expression (3).

H? (DR + 1000) / 6... (3) Expression

Where H is component strength (Hv) and DR is deformation resistance (MPa).

Since the steel for high speed cold working of this invention contains (a) solid solution N or more in predetermined amount, predetermined part strength can be ensured after cold working even if the heat processing of quenching tempering after cold working is abbreviate | omitted. In addition, the steel for high speed cold working of this invention is limited to (b) its high speed cold working (preferably cold working with distortion rate of 100 / s or more), and since (c) the amount of chemical components is optimized, it is favorable cold It shows workability.

The steel for high speed cold working of this invention has a big characteristic that it contains solid solution N more than predetermined amount. By this feature, good cold workability can be imparted to steel parts capable of securing high component strength. However, generally, it is thought that containing a large amount of solid solution N increases the deformation resistance of steel materials, deteriorates mold life, and causes damages such as cracks in parts. The present invention is characterized by maintaining good cold workability by performing cold working at high speed. That is, the steel of this invention is characterized by being used only for the use of high speed cold work. By containing (a) solid solution N or more in a predetermined amount, there is no conventional technical idea of improving the component strength after cold working, and (b) suppressing the damage of solid solution N by high speed cold working and maintaining good cold workability.

Moreover, performing cold work at high speed can contribute to the improvement of the productivity of components, and energy saving.

<Chemical component of high speed cold working steel (basic aspect of the present invention)>

Since the steel for high speed cold working of the basic aspect of this invention is one of the characteristics that the chemical component amount is optimized in order to achieve favorable cold workability, the chemical component and solid-solution N amount of steel are demonstrated below.

(C: 0.03 to 0.6%)

C is an element necessary to secure the strength of the parts for high speed cold work. Therefore, the amount of C was made into 0.03% or more. More preferably, it is 0.04% or more, More preferably, it is 0.05% or more. On the other hand, when there is too much C amount, machinability and cold workability will deteriorate. Therefore, the upper limit of the amount of C was set to 0.6%. More preferable upper limit is 0.5%, More preferably, it is 0.4%.

(Si: 0.005 to 0.6%)

Si is an element used as a deoxidizer in the steelmaking process. If the amount of Si is small, gas is generated in the solidification process due to the lack of deoxidation, and these tend to act as defects, thereby deteriorating the deformability. In order to exhibit this effect effectively, it is necessary to add 0.005% or more. More preferable minimum is 0.008%, and still more preferable minimum is 0.01%. However, excessive addition of Si desaturates the effect of deoxidation, and deteriorates cold workability. Therefore, an upper limit is made into 0.6%. A more preferable upper limit is 0.5%.

(Mn: 0.05-2%)

Mn is an element effective as a deoxidation and desulfurization element in the steelmaking process. If the amount of Mn is small, FeS precipitates in the form of a film at grain boundaries, which significantly lowers the grain boundary strength and deteriorates the deformation ability. In order to exhibit this effect effectively, it is necessary to add Mn 0.05% or more. The minimum with more preferable is 0.1%. However, since excessive addition of Mn deteriorates cold workability, the upper limit is made into 2%. More preferable upper limit is 1.5%, and still more preferable minimum is 1%.

[P: 0.05% or less (not including 0%)]

Although P is an element that is inevitably contained as an impurity, when P is contained in ferrite, it is segregated at the ferrite grain boundary, thereby deteriorating cold workability. In addition, P hardly strengthens the ferrite to increase the deformation resistance. Therefore, although it is preferable to reduce as much as possible from the viewpoint of cold workability, extreme reduction causes an increase in steelmaking cost. Therefore, the upper limit was made into 0.05% in consideration of cold workability and process capability. More preferably, you may be 0.03% or less. However, it is industrially difficult to make P amount 0.

[S: 0.05% or less (not including 0%)]

S is an element that is inevitably contained as an impurity, but forms an inclusion of MnS to deteriorate the deformation ability. Therefore, since it is preferable to reduce as much as possible, the upper limit was made into 0.05% from the viewpoint of the deformation ability. Preferable range is 0.03% or less. On the other hand, S is an effective element for improving machinability and may be actively contained. In consideration of machinability, it is recommended to contain S preferably 0.002% or more, more preferably 0.006% or more.

[N: 0.04% or less (not including 0%)]

Here, the total amount of N in steel is demonstrated. N has the effect of solid-solution in steel and improving the component strength after cold work, and is an important element in this invention. However, when the total amount of N in steel is excess, the amount of solid solution N will become excess, and a crack may arise at the time of cold work. In addition, internal defects in the steel and slab cracks during continuous casting also tend to occur. Therefore, the upper limit of the total amount of N in steel was set to 0.04% from the viewpoint of the deformation capacity of the steel, the stability of the material, and the yield improvement during continuous casting. A more preferable upper limit is 0.03%. In addition, in the basic aspect of this invention, although the minimum of all N amounts is not specifically prescribed, In order to satisfy | fill the lower limit of solid solution N mentioned later, Preferably it is 0.007% or more, More preferably, it is 0.008% or more, More preferably, It contains 0.009% or more.

(Employment N: 0.006% or more)

As mentioned above, the solid solution N has the effect of improving the component strength after high-speed cold working. In order to fully secure the synergistic effect of the parts strength after the high speed cold working, the lower limit thereof was set to 0.006%. The lower limit is preferably 0.007%, and more preferably 0.008%. On the other hand, when the amount of solid solution N becomes excessive, the deformation ability deteriorates. Therefore, N amount of solid solution becomes like this. Preferably it is 0.035% or less, More preferably, it is 0.030% or less, More preferably, it is 0.025% or less. The amount of solid solution N is, of course, not to exceed the total amount of N in the steel. Here, the value of "the amount of employment N" in this invention can calculate the amount of solid solution N in steel by subtracting all the N compounds from the total amount of N in steel based on JISG1228.

(a) The total amount of N in the steel uses inert gas melting-thermal conductivity. The sample is cut out from the test steel material, the sample is placed in a crucible and melted in an inert gas stream to extract N, conveyed to a thermal conductivity cell, and the change in thermal conductivity is measured.

(b) The total amount of N compounds in the steel uses ammonia distillation separation indophenol blue light absorption photometry. A sample was cut out from the test steel material and 10% AA-based electrolyte solution (an electrolyte solution of a non-aqueous solvent system that does not form a passivation film on the surface of the steel, specifically 10% acetylacetone, 10% tetramethylammonium chloride, and remaining part: methanol) Constant current electrolysis is performed. Approximately 0.5 g sample is dissolved and the insoluble residue (N compound) is filtered through a polycarbonate filter having a pore size of 0.1 µm. The insoluble residue is decomposed by heating in sulfuric acid, potassium sulfate and pure Cu chips, and combined with the filtrate. After making this solution alkaline with sodium hydroxide, steam distillation is performed and the ammonia which distilled out is absorbed by dilute acid. Phenol, sodium hypochlorite and sodium pentacyanonitrosyl iron (III) are added to form a blue complex, and the absorbance thereof is measured using a photometer.

The amount of solid solution N in steel is computed by subtracting the total amount of N compounds from the total amount of N in steel calculated | required by the said method.

The basic component composition of the steel of the basic aspect of this invention is iron substantially as mentioned above. However, it is naturally acceptable to include inevitable impurities in the steel depending on the situation of raw materials, materials, manufacturing and maintenance. In addition, the steel of the basic aspect of this invention may contain the following arbitrary elements as needed.

[Al: 0.1% or less (not including 0%)]

Al is basically an element effective as a deoxidation element in a steelmaking process, and is also effective for cracking resistance of steel. If necessary, Al is preferably contained in 0.001% or more, more preferably 0.005% or more. However, since Al has strong affinity with N and forms AlN and reduces the amount of solid solution N, in the basic aspect of this invention, the upper limit in the case of containing Al was made into 0.1%. Al amount becomes like this. Preferably it is 0.05% or less, More preferably, it is 0.03% or less.

[Zr: 0.2% or less (does not contain 0%), Ti: 0.1% or less (does not contain 0%), Nb: 0.1% or less (does not contain 0%), V: 0.5% or less (0 At least one selected from the group consisting of%), Ta: 0.1% or less (does not contain 0%), and Hf: 0.1% or less (does not contain 0%)]

Zr, Ti, Nb, V, Ta, and Hf form an N compound together with N to refine crystal grains and increase the toughness of a component obtained after cold working, and are therefore basically effective elements. Thus, in the basic aspect of the present invention, Zr is preferably 0.002% or more, more preferably 0.004% or more, Ti is preferably 0.001% or more, more preferably 0.002% or more and Nb as necessary. Is 0.001% or more, more preferably 0.002% or more, V is preferably 0.001% or more, more preferably 0.002% or more, Ta is preferably 0.003% or more, more preferably 0.006% or more, and Hf is preferable. Preferably it is 0.002% or more, More preferably, it is recommended to contain 0.004% or more.

On the other hand, since these elements have strong affinity with N and form an N compound to reduce the amount of solid solution N, in the basic aspect of this invention, the upper limit was determined as follows. Zr amount is 0.2% or less, preferably 0.1% or less, more preferably 0.05% or less, still more preferably 0.03% or less, Ti amount is 0.1% or less, preferably 0.05% or less, more preferably 0.03% or less, Nb amount is 0.1% or less, preferably 0.06% or less, more preferably 0.04% or less, V amount is 0.5% or less, preferably 0.2% or less, more preferably 0.1% or less, still more preferably 0.05% or less, Especially preferably, it is 0.03% or less, Ta amount is 0.1% or less, Preferably it is 0.05% or less, More preferably, it is 0.03% or less, Hf amount is 0.1% or less, Preferably it is 0.05% or less, More preferably, it is 0.03% or less. .

[B: 0.0015% or less (not including 0%)]

B is an element which improves the deformation ability of steel by increasing the intensity of a grain boundary. Therefore, in the basic aspect of this invention, it is recommended to contain B preferably 0.0001% or more, More preferably, 0.0002% or more as needed. However, B has strong affinity with N, forms BN, and reduces the amount of solid solution N. Moreover, when BN becomes excess, cold workability will fall. Therefore, when it contains, the amount of B of the basic aspect of this invention is 0.0015% or less, Preferably it is 0.001% or less, More preferably, it is 0.0008% or less.

[Cr: 2% or less (not including 0%)]

Cr, like B, can improve the deformation ability of steel. Therefore, as needed, it is recommended to contain Cr preferably 0.1% or more, more preferably 0.2% or more. However, when Cr also becomes excess, deformation resistance will increase and cold workability will fall. Therefore, when it contains, the amount of Cr is 2% or less, Preferably it is 1.5% or less, More preferably, it is 1% or less.

[Cu: 5% or less (not including 0%)]

Since Cu has an effect of hardening the steel material by distortion aging, the component strength after processing can be improved. Therefore, it is recommended to contain preferably 0.1% or more, more preferably 0.5% or more. However, even if it is added excessively, the effect is saturated, the effect which matches content cannot be expected, and it becomes economically disadvantageous, In addition, it causes the cold workability deterioration and worsens the surface property of a component. For this reason, the upper limit of Cu was 5%. Preferably it is 4% or less, More preferably, it is 3% or less, More preferably, it is 2% or less.

[Ni: 5% or less (does not include 0%) and / or Co: 5% or less (does not contain 0%)]

Ni is effective for improving the deformation ability of ferrite-pearlite steel. Moreover, it is effective for the prevention of the surface defect which arises in the steel material surface at the time of Cu addition. Preferably, it is recommended to contain 0.1% or more, more preferably 0.5% or more. Therefore, when Cu is added, it is preferable to add the same amount as Cu or 70% or more of Cu amount. However, even if it adds exceeding 5%, an effect is saturated and an effect suitable for the addition amount cannot be expected, and it becomes economically disadvantageous, In addition, cold workability deteriorates on the contrary. Therefore, the upper limit of Ni amount was made into 5%. Ni amount becomes like this. Preferably it is 4% or less, More preferably, it is 3% or less, More preferably, it is 2% or less.

Co, like Ni, is effective for improving the deformation ability of ferrite-pearlite steel. Preferably, it is recommended to contain 0.1% or more, more preferably 0.5% or more. However, if it exceeds 5%, the grain boundary strength is lowered and cracks tend to occur in manufacturing processes such as casting and rolling, so the upper limit of the amount of Co is made 5%. Co amount is preferably 4% or less, more preferably 3% or less, still more preferably 2% or less.

[Mo: 2% or less (does not include 0%) and / or W: 2% or less (does not contain 0%)]

Mo has the effect | action which increases the hardness and deformability after a process. Therefore, it is preferable to contain 0.04% or more, more preferably 0.08% or more, and still more preferably 0.1% or more. However, addition of more than 2% deteriorates cold workability. Therefore, the upper limit of Mo amount was made into 2%. Mo amount becomes like this. Preferably it is 1.5% or less, More preferably, it is 1% or less.

W, like Mo, has the effect of increasing the hardness and deformation ability after processing. Therefore, it is preferable to contain 0.04% or more, more preferably 0.08% or more, and still more preferably 0.1% or more. However, addition of more than 2% deteriorates cold workability. Therefore, the upper limit of the amount of W was made into 2%. The amount of W is preferably 1.5% or less, more preferably 1% or less, and still more preferably 0.5% or less.

(Ca: 0.05% or less, REM: 0.05% or less, Mg: 0.02% or less, Li: 0.02% or less, Pb: 0.1% or less, and Bi: at least one selected from the group consisting of 0.1% or less)

Ca, REM, Mg, Li, Pb and Bi are elements which contribute to the machinability improvement of steel. In particular, Li can improve the machinability by lowering the Al-based oxide and making it harmless. Ca, REM, Mg, and Li also have the effect of spheroidizing sulfide-based inclusions such as MnS to increase the toughness and strain of the steel. Therefore, Ca is preferably 0.005% or more, more preferably 0.01% or more, REM is preferably 0.005% or more, more preferably 0.01% or more, and Mg is preferably 0.002% or more, more preferably 0.005% Or more, more preferably 0.008% or more, Li is preferably 0.001% or more, more preferably 0.002% or more, still more preferably 0.005% or more, and Pb preferably 0.005% or more, more preferably 0.01 It is recommended to contain% or more, more preferably 0.02% or more, and Bi in an amount of preferably 0.005% or more, more preferably 0.01% or more, still more preferably 0.02% or more.

However, even if the amount of these elements is excessive, the effect is saturated. Moreover, when Pb amount is excessive, manufacturing problems, such as rolling damage, generate | occur | produce. Therefore, the upper limit in the case of making it contain was defined as mentioned above. The amount of Ca is preferably 0.04% or less, more preferably 0.03% or less, even more preferably 0.02% or less, and the REM amount is preferably 0.04% or less, more preferably 0.03% or less, even more preferably 0.02% or less. , Particularly preferably 0.01% or less, Mg amount is preferably 0.018% or less, more preferably 0.015% or less, still more preferably 0.01% or less, and Li amount is preferably 0.018% or less, more preferably 0.015% or less More preferably, 0.01% or less, Pb amount is preferably 0.09% or less, more preferably 0.08% or less, still more preferably 0.06% or less, and Bi amount is preferably 0.09% or less, and more preferably 0.08% It is as follows.

<Method of manufacturing high speed cold work steel>

Next, the manufacturing method of the high speed cold working steel of this invention is demonstrated. The steel of this invention is characterized by containing the solid solution N amount 0.006% or more. In order to secure this amount of solid solution N, (i) increasing the total amount of N in the steel, reducing the element having a high affinity for N, and (ii) heating the steel to a predetermined temperature or more, and the predetermined cooling rate or more. It is effective to raise the amount of solid solution N by cooling by using.

(i) Method of increasing the total amount of N in steel and reducing the elements having high affinity with N

When steel contains an element with strong affinity with N, such as Al, nitrogen forms Al and an N compound, and as a result, the amount of solid solution N decreases. However, if the total amount of N in steel is more than that, even if Al etc. form all N and N compounds, sufficient amount of solid solution N can be ensured. More specifically, the amount of solid solution N of 0.006% or more can be secured by ensuring the total amount of N that satisfies the following formula (1).

[N]-(14 [Al] / 27 + 14 [Ti] /47.9 + 14 [Nb] /92.9 + 14 [V] /50.9 + 14 [Zr] /91.2 + 14 [B] /10.8 + 14 [Ta ] /180.9 + 14 [Hf] /178.5) ≥ 0.006 ‥‥ (1)

[In formula (1), [] shows the total content (mass%) in the steel of each element.]

(ii) A method of increasing the amount of solid solution N by heating steel above a predetermined temperature and cooling above a predetermined cooling rate.

In addition, when the chemical composition in steel does not satisfy | fill Formula (1), and N compounds, such as Al, are formed in a large quantity, when sufficient solid solution N quantity cannot be ensured, N compound formed by hot rolling etc. will be added to solid solution. After heating and holding a steel at the temperature which melt | dissolves, it can increase the amount of solid solution N by the solid solution heat treatment which quenches and suppresses precipitation of N compound. Specifically, the amount of solid solution N in the steel can be increased by heating the steel to a temperature of Ac ₃ points + 30 ° C. or higher and then cooling it to 500 ° C. or lower at a cooling rate of 0.5 ° C./s or more.

In order to increase the amount of solid solution N, heating temperature is Ac ₃ points + 30 degreeC or more, Preferably Ac ₃ points + 40 degreeC or more, More preferably, Ac ₃ points + 50 degreeC or more. Heat holding time becomes like this. Preferably it is 10 minutes or more, More preferably, it is 30 minutes or more. However, from the viewpoint of manufacturing cost, the heating temperature is Ac ₃ points + 500 ° C. or lower, more preferably Ac ₃ points + 450 ° C. or lower, still more preferably Ac ₃ points + 400 ° C. or lower, particularly preferably Ac ₃ points Up to + 300 ° C. Moreover, heat holding time becomes like this. Preferably it is 2 hours 30 minutes or less, More preferably, it is 1 hour 30 minutes or less.

During this heating and holding, hot working such as drawing, rolling or pressing may be appropriately performed. After heating and holding, preferably at a cooling rate of at least 0.5 ° C./s, more preferably at least 1 ° C./s, more preferably at least 5 ° C./s, up to 500 ° C., at which solid solution N can be stably present, preferably By cooling to 450 degrees C or less, precipitation of N compound can be suppressed and sufficient solid solution N can be ensured.

<Method for manufacturing high speed cold worked parts>

This invention provides one of the characteristics which provide the steel containing the said chemical composition and solid solution N to a high speed cold work. The steel of the present invention contains a relatively large amount of solid solution N, but nevertheless, in order to maintain good cold workability, the steel of the present invention is preferably 100 / s or more, more preferably 120 / s or more, More preferably it is recommended to cold work at a distortion rate of at least 140 / s, particularly preferably at least 150 / s and most preferably at least 200 / s. On the other hand, if the distortion rate is too fast, an adiabatic temperature rise occurs and cracks tend to occur, so the distortion rate is preferably 500 / s or less, more preferably 450 / s or less, and even more preferably 400 / s. Or less, particularly preferably 300 / s or less, most preferably 280 / s or less, especially 260 / s or less.

In addition, since the temperature at the time of processing also affects cold workability, the upper limit of the processing temperature is preferably set to 200 ° C, more preferably 180 ° C, even more preferably 160 ° C. This is because if the processing temperature is too high, dynamic distortion aging occurs during deformation, deformation resistance is increased, and mold life is deteriorated. On the other hand, although cold working is normally performed at room temperature, when it is less than 0 degreeC, since a deformation resistance will increase inversely under the influence of temperature dependency, the minimum with preferable processing temperature shall be 0 degreeC. In addition, processing temperature is an atmospheric temperature at the time of processing.

The steel materials (for example, wire rods and steel bars) manufactured as mentioned above are then cold-worked at high speed on the conditions mentioned above, and become components, such as a bolt and a nut, and other mechanical parts. The cold working method here includes cold working such as cold forging, cold rolling, cold rolling, cold drawing and cold extrusion. Moreover, you may process drawing, rolling, etc. as needed for the process of parts.

It is preferable that the parts manufactured by the high speed cold working have a suitable balance between the part strength and the deformation resistance during the high speed cold working, and the high speed cold working steel is subjected to high speed cold working at a processing temperature of 200 ° C. or lower and a distortion rate of 100 / s or more. In one case, it is preferable that the component strength H of the high speed cold work and the maximum value DR of the deformation resistance during the high speed cold work satisfy the following Equation (3).

H? (DR + 1000) / 6... (3) Expression

However, H is component strength (Hv) and DR is deformation resistance (MPa).

<Embodiment of this invention>

The composition of the basic component and the optional component (optional element) of the steel of the basic aspect of the present invention is as described above. However, the basic aspect of this invention can be classified into the following three embodiments according to a use and the required performance.

<1st aspect of this invention>

The steel for high speed cold working of the 1st aspect of this invention is C: 0.03-0.15%, Si: 0.005-0.6%, Mn: 0.05-2%, P: 0.05% or less (not containing 0%), S : 0.05% or less (not containing 0%), and N: 0.04% or less (not including 0%), the remainder being made of iron and unavoidable impurities, and the amount of solid nitrogen in steel is 0.006% or more. It is characterized by.

(C: 0.03 to 0.15%)

In the first embodiment of the present invention, in order to realize good machinability and cold workability, the upper limit of the amount of C is set at 0.15%. A more preferable upper limit is 0.12%. The lower limit of the amount of C is 0.03%, preferably 0.04% in order to secure the strength of the steel.

Description other than the amount C in the first embodiment of the present invention (ie, other basic components and optional components (arbitrary elements), steel production method, component production method, component strength and balance between deformation resistance during high speed cold working) Description of Formula (3) and the like are the same as those described above in the basic aspect of the present invention.

Second Embodiment of the Present Invention

The steel for high speed cold working of the 2nd aspect of this invention is C: more than 0.15 to 0.6%, Si: 0.005 to 0.6%, Mn: 0.05 to 2%, P: 0.05% or less (not containing 0%), S: 0.05% or less (does not contain 0%), and N: 0.04% or less (does not contain 0%), respectively, the remainder being made of iron and inevitable impurities, and the content of N as a solid solution state This is characterized by being 0.006% or more.

(C: greater than 0.15 to 0.6%)

In the second embodiment of the present invention, the amount of C is set to more than 0.15% in order to realize higher component strength. More preferably, it is 0.16% or more, More preferably, it is 0.17% or more. On the other hand, when there is too much C amount, machinability and cold workability will deteriorate. Therefore, the upper limit of the amount of C is 0.6%, Preferably it is 0.5%, More preferably, it is 0.4%.

Description other than the amount C in the second embodiment of the present invention (ie, other basic components and optional components (optional elements), steel production method, component production method, component strength and balance between deformation resistance during high speed cold working) Description of Formula (3) and the like are the same as those described above in the basic aspect of the present invention.

<3rd embodiment of this invention>

In the third embodiment of the present invention, it is described to reduce the amount of elements (Al, Ti, Nb, V, Zr, B, Ta, Hf) that reduce solid solution N. Thereby, sufficient amount of solid solution N can be ensured and higher component strength can be achieved, maintaining favorable cold workability.

That is, the steel for high speed cold working of the 3rd aspect of this invention is C: 0.03%-0.6%, Si: 0.005-0.6%, Mn: 0.05-2%, P: 0.05% or less (it does not contain 0%) , S: 0.05% or less (not containing 0%), N: 0.008% to 0.04%, respectively, the remainder being made of iron and inevitable impurities, and in the impurities, Al: 0.001% or less (0% Ti: 0.002% or less (including 0%), Nb: 0.001% or less (including 0%), V: 0.001% or less (including 0%), Zr: 0.001% or less (including 0%) ), B: 0.0001% or less (including 0%), Ta: 0.0001% or less (including 0%), Hf: 0.0001% or less (including 0%), and satisfies the following formula (2). .

14 [Al] / 27 + 14 [Ti] /47.9 + 14 [Nb] /92.9 + 14 [V] /50.9 + 14 [Zr] /91.2 + 14 [B] /10.8 + 14 [Ta] /180.9 + 14 [Hf] /178.5? 0.002%. (2)

[In formula (2), [] shows the total content (mass%) in the steel of each element.]

(N: 0.008% to 0.04%)

The lower limit of the total amount of N in the third embodiment of the present invention is 0.008% in order to secure the amount of solid solution N. The lower limit is preferably 0.009%. On the other hand, the upper limit of the total amount of N is 0.04%, Preferably it is 0.03% from a viewpoint of the deformation ability of steel, the stability of a material, and the yield improvement at the time of continuous casting.

Al, Ti, Nb, V, Zr, B, Ta, Hf may be contained as said unavoidable impurity. These Al etc. are easy to combine with solid solution N, and have an effect which reduces the amount of solid solution N in steel. Therefore, in the 3rd Embodiment of this invention, content when these elements are contained was prescribed | regulated as follows.

[Al: 0.001% or less (including 0%), Ti: 0.002% or less (including 0%), Nb: 0.001% or less (including 0%), V: 0.001% or less (including 0%), Zr : 0.001% or less (including 0%), B: 0.0001% or less (including 0%), Ta: 0.0001% or less (including 0%), Hf: 0.0001% or less (including 0%)]

Al, Ti, Nb, V, Zr, B, Ta, Hf combine with solid solution N, reduce the amount of solid solution N, and form nitrides (AlN, TiN, NbN, VN, ZrN, BN, TaN, HfN) do. These nitrides act to strengthen the precipitation of steel and prevent grain coarsening, thereby increasing deformation resistance. In order to secure a sufficient amount of solid solution N and to achieve good deformation resistance, the lower the amount of Al or the like, the better.

Therefore, the amount of Al in the third embodiment of the present invention is 0.001% or less, preferably 0.0005% or less, Ti amount is 0.002% or less, preferably 0.001% or less, and Nb amount is 0.001% or less, preferably 0.0005% or less. , V amount is 0.001%, preferably 0.0005% or less, Zr amount is 0.001% or less, preferably 0.0005% or less, B amount is 0.0001% or less, preferably 0.00005% or less, Ta amount is 0.0001% or less, preferably 0.00005% Hereinafter, the amount of Hf is 0.0001% or less, preferably 0.00005% or less. The most preferable contents of Al, Ti, Nb, V, Zr, B, Ta and Hf are each 0%.

Although content of Al, Ti, Nb, V, Zr, B, Ta, and Hf needs to be individually below the above-mentioned regulation, in order to ensure sufficient amount of solid solution N in steel, the relationship of following formula (2) It is necessary to satisfy.

14 [Al] / 27 + 14 [Ti] /47.9 + 14 [Nb] /92.9 + 14 [V] /50.9 + 14 [Zr] /91.2 + 14 [B] /10.8 + 14 [Ta] /180.9 + 14 [Hf] /178.5? 0.002%. (2)

For example, the term (14 [Al] / 27) is a term indicating the amount of nitrogen present in the steel in the form of AlN, and in the entire left side of the formula (2), Al, Ti, Nb, V, Zr, B , Total of the amount of nitrogen in the state of bonding with any one of Ta and Hf (total amount of N compounds in steel). Therefore, in order to ensure the amount of solid solution N, since the smaller one is preferable, it was made into 0.002% or less. More preferably, it is 0.0018% or less, More preferably, it is 0.0016% or less.

Description other than the amounts of N, Al, Ti, Nb, V, Zr, B, Ta, and Hf in the third embodiment of the present invention (that is, other basic components, optional components (optional elements), and a method for producing a part) The balance between the component strength and the deformation resistance during the high-speed cold working (explanation of the above (3) formula, etc.) is the same as described above in the basic aspect of the present invention. In the third embodiment of the present invention, the high speed cold working steel may be manufactured by the above-described manufacturing method. However, if (2) is satisfied, the amount of solid solution N in the steel can be secured without depending on the manufacturing process. have.

Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not restrict | limited by the following example, Of course, it is also possible to change suitably and to implement in the range which may be suitable for the objective of the previous period. They are all included in the technical scope of the present invention.

<First Example (Examples of the Invention and Comparative Example of the First Aspect of the Present Invention)>

First, the steel which has the chemical composition of Table 1-Table 3 was melted by the converter, it was made into steel slab by continuous casting, and it rolled with the wire of (phi) 12mm.

The obtained wire rod was subjected to heat treatment under the conditions shown in Table 4. After the heat treatment of the conditions shown in Table 4, it is preferable to set the holding time of 10 minutes or more, preferably 30 minutes or more. Then, the test piece of (phi) 4 mm x 6 mm was cut out from the center part of the wire rod which performed the said heat processing. In addition, Tables 1-3 show whether each test piece satisfy | fills said Formula (1), and when it satisfy | fills Formula (1), when it does not satisfy "(circle)" and (1), it is "x." Is given. In addition, in the table, "employment N" represents the amount of solid solution N, and "N" represents the total amount of nitrogen.

Next, the processing specimen test apparatus of the capacity | capacitance 200kN is carried out for the test piece of Tables 1-3, under the processing conditions of distortion rate: 0.001-240 / s, processing temperature: 20-400 degreeC, and compression ratio: 20-80%. Forging was used to machine the parts. The distortion speed used the average value of the distortion speed during processing (during plastic deformation). About the obtained component, the surface was observed with the actual microscope at 20 times the observation magnification, and the presence or absence of the crack was confirmed. The processing conditions, presence of cracks and deformation resistance of each part are shown in Tables 5 to 7.

The Vickers hardness (Hv) of the part was measured using a Vickers hardness tester under load: 1000 g, measurement position: D / 4 center part (D: part diameter) of the test piece cross section, and measurement number: 5 times. The hardness (Hv) of each component is shown in Tables 5-7.

In the present Example, it was judged that the steel which does not have a crack and whose deformation resistance of steel is low with respect to component hardness (specifically, satisfy | filling said Formula (3)) is excellent in cold workability.

Moreover, the component whose Vickers hardness (Hv) of the component was 240 or more was determined to be excellent in strength. In addition, Tables 5 to 7 show whether each test piece satisfies the above Equation (3), and when satisfying the Equation (3), &quot; (circle) &quot; X "is given.

From Tables 5 to 7, in the preferred processing conditions (distortion rate and processing temperature), the steel that satisfies the requirements of the chemical component amount and the solid solution nitrogen amount defined in the first embodiment of the present invention is excellent in cold workability. It can be seen that the parts obtained from the above have excellent strength. On the other hand, the thing which does not satisfy the requirements prescribed | regulated by 1st Embodiment of this invention is inferior to cold workability or component strength, as described below.

Since the part number I-1 (steel number I-1A) had a small amount of carbon, the hardness (Hv) was less than 240, and the strength was insufficient.

Part number I-6 (steel number I-1F) had a large amount of carbon, so that a crack occurred in the part.

Part number I-7 (steel number I-1G) had a small amount of Si, so that a crack occurred in the part.

Since part number I-14 (steel number I-1N) has many Si amounts, the crack generate | occur | produced in the part.

Part number I-15 (steel number I-10) had a small amount of Mn, so that a crack occurred in the part.

Part number I-24 (steel number I-1X) had a large amount of Mn, so that a crack occurred in the part.

Part numbers I-25 and I-26 (steel numbers I-1Y and I-1Z) had a large amount of P, and cracks occurred in the parts.

Second Example (Examples of the Invention and Comparative Example of the Second Aspect of the Present Invention)

First, the test steels (units in the table are% by mass) of steel symbols II-1A to II-4A made of the chemical components shown in Tables 8 to 10 were dissolved by converters, and then made into steel pieces under a continuous casting method. Diameter) 12 mm. Thereafter, heat treatment shown in Table 11 was performed. Moreover, after the heat processing of the conditions shown in Table 11, it is preferable to set the holding time of 10 minutes or more, Preferably it is 30 minutes or more.

Then, the test piece of 4 mm x L (length) 6 mm of (diameter) was cut out from the center part of the wire rod which heat-processed above. In addition, Tables 8-10 show whether each test piece satisfy | fills said Formula (1), and when it satisfies Formula (1), "(circle)" is written, and when it does not satisfy, it writes "x". . In Tables 8 to 10, "employment N" represents the amount of solid solution N, and "N" represents the total amount of N.

Next, the processing specimen test of the capacity 200kN was carried out on the test piece of Table 8-10 by the processing conditions of processing distortion rate: 0.001-240 / s, processing temperature: 20-400 degreeC, and compression ratio: 20-80%. The device was forged and processed into parts. The processing distortion speed used the average value of the distortion speed during processing (during plastic deformation).

About the obtained component, the surface was observed at 20 times the observation magnification using a stereo microscope, and the presence or absence of the crack was confirmed. The processing conditions, presence of cracks and deformation resistance of each part are shown in Tables 12 to 14.

In addition, the load: 1000 g, the measurement position: D / 4 position center part (D: part diameter) of the test piece cross section, and the number of measurements: 5 conditions, the Vickers hardness (Hv) of a part is measured using the Vickers hardness tester. It was. The hardness (Hv) of each component is shown in Tables 12-14.

In the present Example, it was judged that the steel which does not have a crack and whose deformation resistance of steel is low with respect to component hardness (specifically, satisfy | filling said Formula (3)) is excellent in cold workability. In addition, as part strength required, it was made on condition that Vickers hardness (Hv) was 240 or more.

In addition, Tables 12 to 14 show whether each test piece satisfies the above Equation (3), and when satisfying the Equation (3), &quot; (circle) &quot; X "is written.

From Tables 12 to 14, in the preferred processing conditions (distortion rate and processing temperature), the steels satisfying the requirements of the chemical component amount and the solid solution N amount specified in the present invention are excellent in cold workability, and the parts obtained from the It is understood that no crack is generated and the part strength is excellent.

On the other hand, the thing which does not satisfy | fill the requirement prescribed | regulated by this invention turns out that a crack generate | occur | produces or does not satisfy | fill Formula (3), and the balance of cold workability and component hardness is bad, as described below.

Part number II-1 is an example using the steel symbol II-1A whose amount C is less than the prescribed range of 2nd Embodiment of this invention, and does not reach the range prescribed | regulated by the hardness after processing.

Part number II-6 is an example using the steel symbol II-1F whose amount C exceeds the prescribed range of 2nd Embodiment of this invention, and the crack generate | occur | produced in the part.

Part number II-7 is an example using the steel symbol II-1G whose Si amount is less than the prescribed range of the 2nd Embodiment of this invention, and a crack generate | occur | produced in the part.

Part number II-14 is an example using the steel symbol II-1N in which the amount of Si exceeds the prescribed range of the second embodiment of the present invention, and cracks occurred in the part.

Part number II-15 is an example using the steel symbol II-10 whose Mn amount is less than the prescribed range of the 2nd aspect of this invention, and the crack generate | occur | produced in the part.

Part number II-24 is an example using the steel symbol II-1X whose Mn amount exceeds the prescribed range of 2nd Embodiment of this invention, and the crack generate | occur | produced in the component.

Part number II-25 and number II-26 are the examples using the steel symbols II-1Y and II-1Z in which P amount exceeds the prescribed range of 2nd Embodiment of this invention, and the crack generate | occur | produced.

Part number II-27 and part number II-28 are the examples using the steel symbols II-2A and II-2B in which S quantity exceeds the prescribed range of 2nd Embodiment of this invention, and the crack generate | occur | produced.

Part number II-29 is an example using the steel symbol II-2C in which the amount of N is less than the preferred prescribed range (0.007% or more) of the second embodiment of the present invention, and the amount of solid solution N is the second embodiment of the present invention. The balance between cold workability and hardness is poor because it is less than the prescribed range of. That is, the above formula (3) is not satisfied.

Part number II-42 is an example using the steel symbol II-2K in which N quantity exceeds the prescribed range of the 2nd Embodiment of this invention, and the crack generate | occur | produced.

Part Nos. II-31 to II-34 use steel materials of the steel symbol II-2E whose chemical component amounts satisfy the requirements of the second embodiment of the present invention. Aging occurred and cracks occurred.

Although the part numbers II-37 to II-38 use steel materials of steel symbols II-2F to II-2G whose chemical composition amounts satisfy the provisions of the second embodiment of the present invention, the temperature at the time of high-speed cold working is high. Therefore, dynamic distortion aging occurred and cracks occurred.

The steel symbol II-2S corresponding to the part number II-50 does not satisfy the formula (1), so the amount of solid solution N is less than the prescribed amount (Table 9). For this reason, the part number II-50 has the bad balance of cold workability and hardness (it does not satisfy | fill Formula (3)). However, even when the expression (1) is not satisfied, depending on the method of the heat treatment pattern, the amount of solid solution N may satisfy the prescribed range of the second embodiment of the present invention (for example, the material of Table 10). No. II-73 to II-75, No. II-78 to II-79, No. II-81 to II-83, No. II-86 to II-87, No. II-90 to II-91, No. II-93 to II-95, numbers II-98 to II-99, numbers II-101 to II-103).

Part number II-77, part number II-81 to II-82, part number II-85, part number II-89 to II-90, part number II-93 to II-94, part number II-97, part number II-101 to II-102 and part number II-105 are examples using the steel symbols II-2S and II-3T to II-4A whose chemical composition amounts satisfy the provisions of the second embodiment of the present invention. Since the suitability with each of the applied manufacturing conditions (heat treatment patterns II-a to II-j in Table 11) did not match, a predetermined amount of solid solution N could not be obtained. As a result, the expression (3) was not satisfied. That is, the balance of cold workability and component hardness was bad.

<Example 3 (Inventive Example and Comparative Example Regarding Third Embodiment of the Present Invention)>

First, test steels of steel symbols III-1A to III-3S made of the chemical components shown in Tables 15 and 16 (units are% by mass) are listed for convenience in order to describe the numbers of cold-worked parts to be described later). And a steel strip under a continuous casting method, and then rolled with a wire having a diameter of 12 mm. Thereafter, the wire rod was subjected to a heat treatment such as heating → (hot working) → cooling. This heat treatment was performed in the patterns III-a to III-j as shown in Table 17. Moreover, after the heat processing of the conditions shown in Table 17, it is preferable to provide the holding time of 10 minutes or more, Preferably it is 30 minutes or more.

Subsequently, the test piece of 4 mm x L (length) 6 mm of (diameter) was cut out from the wire center part which performed the said heat processing.

In Table 15 and Table 16, "N" represents the total amount of N (mass%), and "employment N" represents the amount of solid solution N (mass%) "N compound" represents the amount of N compounds (mass%). As described above, the amount of solid solution N was calculated by subtracting the amount of N compounds from the total amount of N in steel in accordance with JIS G1228.

Next, the test pieces shown in Tables 15 and 16 were subjected to a processing former test having a capacity of 200 kN under processing conditions of processing distortion rate: 0.001 to 240 / s, processing temperature: 20 to 400 ° C, and compression ratio: 20 to 80%. The device was forged and processed into parts. The processing distortion speed used the average value of the distortion speed during processing (during plastic deformation).

About the obtained component, the surface was observed at 20 times the observation magnification using a stereo microscope, and the presence or absence of the crack was confirmed. The processing conditions, presence of cracks and deformation resistance of each part are shown in Tables 18 and 19.

In addition, the load: 1000 g, the measurement position: D / 4 position center part (D: part diameter) of the test piece cross section, and the number of measurements: 5 conditions, the Vickers hardness (Hv) of a part is measured using a micro Vickers hardness tester. It was. The hardness (Hv) of each component is shown in Table 18 and Table 19.

In the present Example, it was judged that the steel which does not have a crack and whose deformation resistance of steel is low with respect to component hardness (specifically, satisfy | filling said Formula (3)) is excellent in cold workability. As the component strength, one having a Vickers hardness of 240 (Hv) or more is recommended.

In addition, Table 18 and Table 19 show whether each test piece satisfies the above Equation (3), and when satisfying the Equation (3), &quot; X "is written.

From the result of Table 18 and Table 19, it can consider as follows.

Part numbers III-2 to III-5 (steel symbols III-1B to III-1E), part numbers III-8 to III-13 (steel symbols III-1H to III-1M), part numbers III-16 to III- 23 (steel symbol III-1P to III-1W), part number III-30 (steel symbol III-2D), part number III-35 to III-36 (steel symbol III-2E), part number III-39 to III -41 (steel symbol III-2H to III-2J), part number III-43 to III-49 (steel symbol III-2L to III-2R), part number III-51 (steel symbol III-2T), part number III-55 to III-56 (steel symbols III-2X to III-2Y) and part numbers III-58 to III-76 (steel symbols III-3A to III-3S) are all of the third embodiment of the present invention. It is the example which performed high speed cold working by the method recommended by this invention using the steel grade which satisfy | fills a prescription | regulation. All of the high speed cold work parts (wire rods and bars) indicated by the above part numbers are excellent in balance between cold workability and strength (hardness) and crack resistance.

On the other hand, in the following examples which do not satisfy the requirements specified in the third embodiment of the present invention, as described above, cracks occur in the high-speed cold worked parts, or the balance between cold workability and strength (hardness) is poor. [The above formula (3) is not satisfied].

Part number III-1 is an example using steel symbol III-1A with a small amount of C, and cracks occur after machining.

Part number III-6 is an example using steel symbol III-1F with a large amount of C, and since C exceeds a predetermined range, cracking occurs.

Part number III-7 is an example using steel symbol III-1G having a small amount of Si, and since Si is less than a predetermined range, cracking occurs.

Part number III-14 is an example of using steel symbol III-1N having a large amount of Si. Since Si exceeds a predetermined range, cracking occurs.

Part number III-15 is an example in which steel symbol III-10 having a small Mn amount is used. Since Mn is smaller than a predetermined range, cracking occurs.

Part number III-24 is an example using the steel symbol III-1X with much Mn amount, and since Mn exceeds the predetermined range, a crack occurs.

Part numbers III-25 and III-26 are examples using steel symbols III-1Y and III-1Z with a large amount of P. Since P exceeds a predetermined range, cracking occurs.

Part Nos. III-27 and III-28 are examples in which steel symbols III-2A and III-2B with a large amount of S are used, and since S exceeds a predetermined range, cracking occurs.

Part number III-29 is an example using the steel symbol III-2C with a small amount of N. Since N is smaller than a predetermined range and the amount of solid solution N is small, the balance between cold workability and hardness is poor.

Part number III-42 is an example using steel symbol III-2K with a large amount of N. Since N exceeds a predetermined range, cracking occurs.

Part Nos. III-31 to III-34 use steel materials of the steel symbol III-2E having the component composition satisfying the provisions of the third embodiment of the present invention. Occurs and cracks occur.

Part Nos. III-37 to III-38 use steel materials of the steel symbols III-2F to III-2G of the component composition satisfying the provisions of the third embodiment of the present invention, but the temperature at the time of high-speed cold work is high, Dynamic distortion aging occurs and cracks occur.

Part number III-50 is an example using the steel symbol III-2S which has a large amount of Al and does not satisfy | fill Formula (2), and its balance of cold workability and hardness is bad.

Part number III-52 is an example using the steel symbol III-2U which has many amounts of Al and B, and does not satisfy | fill Formula (2), and the balance of cold workability and hardness is bad.

Part number III-53 is an example using the steel symbol III-2V which has many Ti amounts and does not satisfy | fill Formula (2), and its balance of cold workability and hardness is bad.

Part number III-54 is an example using the steel symbol III-2W which has many V quantities and does not satisfy | fill Formula (2), and is bad in the balance of cold workability and hardness.

Part No. III-57 is an example in which there are many amounts of Ti, V, and B, and uses steel symbol III-2Z that does not satisfy the formula (2), and the balance between cold workability and hardness is poor.

Claims (15)

C: 0.03% to 0.6% (mean of mass%, the same below), Si: 0.005 to 0.6%, Mn: 0.05 to 2%, P: 0.05% or less (not including 0%), S: 0.05% or less (not including 0%), N: 0.04% or less (does not contain 0%), The remainder is made of iron and unavoidable impurities, and the amount of solid nitrogen in the steel is 0.006% or more. The steel for high speed cold working according to claim 1, wherein the content of C is 0.03 to 0.15%. The steel for high speed cold working according to claim 1, wherein the content of C is more than 0.15 to 0.6%. The steel for high speed cold working of Claim 1 containing N: 0.007% or more. The steel for high speed cold work according to claim 1, further comprising Al: 0.1% or less (not including 0%). The method of claim 1, further comprising Zr: 0.2% or less (not including 0%), Ti: 0.1% or less (not including 0%), Nb: 0.1% or less (not including 0%), V: 0.5% or less (not including 0%), Ta: 0.1% or less (not including 0%), Hf: High-speed cold working steel containing at least 1 sort (s) chosen from the group which consists of 0.1% or less (it does not contain 0%). The steel for high speed cold working according to claim 1, which further contains B: 0.0015% or less (does not contain 0%) and / or Cr: 2% or less (does not contain 0%). The steel for high speed cold working of Claim 1 which satisfy | fills following formula (1). [N]-(14 [Al] / 27 + 14 [Ti] /47.9 + 14 [Nb] /92.9 + 14 [V] /50.9 + 14 [Zr] /91.2 + 14 [B] /10.8 + 14 [Ta ] /180.9 + 14 [Hf] /178.5) ≥ 0.006 ‥‥ (1) [In formula (1), [] shows the total content (mass%) in the steel of each element.] The method of claim 1, wherein the content of the unavoidable impurities is Al: 0.001% or less (including 0%), Ti: 0.002% or less (including 0%), Nb: 0.001% or less (including 0%), V: 0.001% or less (including 0%), Zr: 0.001% or less (including 0%), B: 0.0001% or less (including 0%), Ta: 0.0001% or less (including 0%), Hf: High speed cold working steel which satisfies 0.0001% or less (including 0%) and satisfies the following formula (2). 14 [Al] / 27 + 14 [Ti] /47.9 + 14 [Nb] /92.9 + 14 [V] /50.9 + 14 [Zr] /91.2 + 14 [B] /10.8 + 14 [Ta] /180.9 + 14 [Hf] /178.5 ≤ 0.002% ‥‥ (2) [In formula (2), [] shows the total content (mass%) in the steel of each element.] The method of claim 1, further comprising: Cr: 2% or less (does not include 0%), Cu: 5% or less (does not include 0%), Ni: 5% or less (does not contain 0%), Co: 5% or less (without 0%), Mo: 2% or less (without 0%), W: 2% or less (without 0%), Ca: 0.05% or less (0% Rare earth elements: 0.05% or less (does not contain 0%), Mg: 0.02% or less (does not contain 0%), Li: 0.02% or less (does not contain 0%), Pb : High speed cold working steel containing at least 1 sort (s) chosen from the group which consists of 0.1% or less (it does not contain 0%), and Bi: 0.1% or less (does not contain 0%). The high speed cold working steel of any one of Claims 1-10 is cold-worked at the processing temperature of 200 degrees C or less, The manufacturing method of the high speed cold working part characterized by the above-mentioned. The high speed cold working steel of any one of Claims 1-10 is cold-worked at a distortion speed of 100 / s or more, The manufacturing method of the high speed cold working part characterized by the above-mentioned. Any one of claims 1 to 8 After heating a steel material having component composition according to any one of items at a temperature Ac ₃ point + 30 ℃ or more, and the hot working in the temperature range Ac ₃ point + 30 ℃ or more, more than 0.5 ℃ / s A method for producing a high speed cold working steel, which is cooled to 500 ° C. or lower at a cooling rate. After heating the steel material which has a component composition as described in any one of Claims 1-8 to the temperature of Ac ₃ point + 30 degreeC or more, it cools to 500 degrees C or less at the cooling rate of 0.5 degreeC / s or more, The high speed characterized by the above-mentioned. Method for manufacturing cold work steel. The high speed cold working part manufactured by the high speed cold working steel of any one of Claims 1-10 at a processing temperature of 200 degrees C or less and a distortion rate of 100 / s or more, and is the component strength after high speed cold working. (H) and the maximum value DR of the deformation resistance during the high speed cold working satisfy the following formula (3). H? (DR + 1000) / 6... (3) Expression Where H is component strength (Hv) and DR is deformation resistance (MPa).