JPS5996246A - Steel wire for cold formed spring of extra high strength its production and cold formed spring of extra high strength obtained from said steel wire - Google Patents

Abstract

PURPOSE:To produce a titled steel wire having high toughness and high resistance to permanent set by subjecting a hot-rolled material incorporated with specific proportion of C, Si, N, Cr, V in Fe to hardening and tempering by quick heating and quick cooling thereby forming ultrafine crystal grains. CONSTITUTION:A hot-rolled material consisting, by weight, 50-0.60% C, 1.20- 1.60% Si, 0.60-0.80% Mn, 0.60-0.80% Cr, added with 0.10-0.50V, and consisting of the balance Fe and unavoidable impurities is heated, after drawing, at the prescribed heating temp. (higher by 50-100 deg.C than for a material contg. no V) at a heating rate of >=100 deg.C/sec and is then quickly cooled at a cooling rate of >=100 deg.C/sec. Said material is then heated to a prescribed tempering temp. at a heating rate of >=100 deg.C/sec and is quickly cooled. The steel wire for a cold formed extra high strength spring finished to >=180kgf/mm.<2> tensile strength is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultra-high-strength cold-formed spring steel wire, a method for manufacturing the same, and an ultra-high-strength cold-formed coil spring made from the Puoka wire.

When vanadium V is added at a concentration of 6 fM, (1) the number of crystal nuclei increases due to the precipitation of carbides, and the grain growth suppressing action of these compounds causes the crystal grains to become fine 11-stage grains. However, when heat-treating steel materials containing ■, carbides and the like become solid solutions and become IL, compared to steel materials that do not contain ■. Seal: It is necessary to raise the passion level to 6-mome, and the degree of 1 kou will follow the increase of V-addition leaves. On the other hand, the above-mentioned increase in the degree of quenching heating 61 occurs at the time of required heating], which leads to coarsening of crystal grains.
The grain refining effect of Nj material is shown in “1.
, 1 layer 'll' This is offset by the phenomenon of one grain enlargement, and in the conventional example, 'Q-0,' heat-treated products with 15 to 0.20% by weight added have crystal grains with a grain size number of 8 to 9. I don't like it.

In today's world where there is a strong demand for high strength coil springs, Fugenmeisha has high toughness and high tenacity despite being ultra-high strength?
We believe that ultra-fine crystal grains are extremely effective in obtaining 1ilf wire for cold-formed springs, so we added vl to a material equivalent to 5AE9254, which is a conventional steel type for springs, and By applying full heat treatment to suppress the enlargement of
■Ultra-high-strength cold that fully brings out the effects of addition] 111 for molding spatter i? ::ll) Gland and its manufacturing method and the same, ε11・'j 1lii! The purpose of the present invention is to provide an ultra-high strength (/l''iji:i) formed coil spring obtained by the above method, thereby meeting the requirements of the above article.

The gist of the first invention of the present application is that the weight component ratio C: 0, 50 to 0.
60%, S too; 1. 2 0 ~ 1.6
0%.

Mn: 0.60-0.80%, Cr: 0.6
Contains 0 to 0.80%, and V; 0.10 to
The crystal grains of the wire rod obtained by subjecting a hot-rolled material with 0.50% roughness and the remainder consisting of h and unavoidable impurities to quenching and subsequent reconditioning heat treatment by rapid heating and rapid cooling are ultra-fine. The special feature is super 17.5 strength cold-formed spring steel wire.

However, book 11. U1 First Invention of God's Honho”
The gist of the second invention is as follows: (1) Weight component ratio C: 0.50 to 0.60, Si
; 1, 20-1.60%, Mfr;
0. 60-080 chi.

Cr; Contains 0.60-0.80%'f, and ■
; A hot-rolled material with 0.10 to 0.50% added and the remainder consisting of h and unavoidable impurities is (2) drawn out and then heated to 7.11 degrees at 100 degrees C/sec or more to a predetermined θ' Heating Wr' at a time 1 (3) Cooling rate IMi' of 1-00℃/sec or more
(4) Subsequently, the stones were heated at a heating rate of 100°C/sec or more to the tempering temperature in place, cooled, and (5) 11 stones finished with a tensile strength of 180 Kgf/mm' or more. The present invention provides a method for producing an ultra-high steel wire for cold-formed springs, which is characterized by having 4m strength and 1'1 shoulder U] settability.

'8j:/KO,'21;Kihonkuryo1 a' 1Zu Nishimei 3The gist of the invention is as follows: (1) Weight component ratio C; 0.50 to 0 .6'18. , S: 1.20-1.60%, Mausoleum: 0.60-0.80%.

Total content of Cr; 0.60 to 0.80%, and V; 0
．． Coil springs obtained by applying a heat treatment consisting of rapid heating, bathing, and rapid cooling to a hot-rolled material with the addition of 10 to 0.50% and the remainder consisting of h and unavoidable impurities. However, it is an ultra-high-strength cold-formed coil that (2) has excellent resistance to 1-μm dull softening at low temperatures, and (3) has all of the following: It's on the edge.

The invention will be described in detail below.

The technical idea of g1 of the present invention is to add a relatively large amount of ■f to the wire rod, which has conventionally been classified as non-resistance type 1, and to increase the quenching heating temperature, which inevitably increases due to the addition of V. The purpose is to suppress coarsening of crystal grains caused by the extension of the heating time required to reach a high heating temperature by quenching by rapid heating and rapid cooling. That is, the material of the high-strength gland material for additive cold-formed springs, which has been adjusted to a predetermined wire diameter by drawing, can be sufficiently austenitized at a temperature of 50 to 100° C. higher than the actual filling temperature of all non-V-containing materials, for example, 900. ~
],, 100℃/s at quenching heating temperature of 050℃
The temperature is raised at a heating rate of e c or higher. In this case, the heating time is extremely rapid, such that the heating time is within 3 Q see, including the holding time taken to achieve austenitization up to the center of the wire, if necessary. Short-time heating in which the time for residence in the high-temperature zone is extremely short is preferred. By doing this, the heating temperature is set at the same temperature as ``2'' without giving ti:ii when the crystal grains coarsen, and the wire rod that has reached that temperature is heated to 1.
It is immediately quenched at a cooling rate of 00° C./sec or higher, and the quenching further prevents coarsening of crystal grains and sufficiently hardens it.

The technical idea of item 32 of the present invention is that even in the tempering that is applied after the above-mentioned quenching, the wire rod is heated at a heating rate of 100.
V in the matrix by rapidly heating to a predetermined tempering temperature, e.g., between 300 and 650°C, at a temperature of 100°C/3eC or more, and rapidly cooling at a cooling rate of 100°C/3eC or more.
Enriched zones are formed frequently, thereby suppressing the agglomeration and growth of Cr carbides, and reducing strain convergence following cold forming performed after the tempering.
'14 also eliminates the possibility of precipitation hardening. This force is enriched with the frequently occurring ■.The V in the head region is increased by 1α due to the cold coiling process, and the dislocation energy ′(il-
The aim is to make it easier to produce carbide.

In other words, due to the interaction between ■, C, and dislocations, the subsequent strain relief is achieved with low i'A'! Precipitation hardening is promoted during annealing, and this becomes a factor that results in extremely high softening resistance. The higher the treatment temperature, the more effective low-temperature annealing for strain relief is in stabilizing the durability of coil springs. Strength decreases during annealing. In other words, the temperature of the annealing treatment controls the increase in strength of the wire, so if there is resistance to Europeanization, a high annealing temperature will result in a +Iil Kusumi price. , it becomes possible to obtain the full strength of a coil of 25 strength. Therefore, due to the tempering process, the wire rod is made of Cr.
As a result of completely suppressing the agglomeration and growth of carbides, the structure becomes fine and cold formability is ensured, and as a result of this cold formability, the tensile strength is 1801 (7f / nnn2 or more).
Second, to achieve ultra-high strength, for example, 200 i<yf/mm2.

By implementing the above first and second technical ideas, the effect of adding ■ to the spring wire material is maximized, ultra-fine crystal grains and microstructures are achieved, and high toughness and high durability are achieved. - To obtain an ultra-high strength copper wire for springs that has high l1w and excellent cold formability.

[19] The author of this paper first investigated how the addition of V to the spring wire of the present invention and the quenching by rapid heating and rapid cooling interact with each other, and how the addition of V to the spring wire of the present invention interacts with each other, and Experiment 1 and Experiment 1 and 2 below were conducted in order to confirm how tempering would produce a synergistic sound effect for the wire rod subjected to rapid quenching with the addition of (1).

Experiment 1゜(1) The 5AE9254 equivalent system, also known as jjiij, and the corresponding material were tested with v-2 of 0.12, 0.24, 0.37, and 0.0, respectively. Using the five types of heat 1"4jEE rolled wire shown in Table 1 with 53 weight and 65 added as specimens, each of these specimens was sized to 1.Q mmφ by drawing, and each A full quenching and tempering heat treatment consisting of rapid heating and through cooling was carried out, and the grain size of the obtained heat-treated GIWj wire was examined.

(2) Heat treatment] Jj condition quenching heating temperature is 900℃ for specimen (), specimen (■)
The temperature was set at 1,050°C, and the test specimens (L[), (III) and (l~) were set at an intermediate temperature between the above temperatures as the amount of V added increased.

The ILl
The material was rapidly cooled and quenched under conditions depending on the composition. The heating temperature, heating rate, and cooling rate for tempering were kept constant for all specimens.

Incidentally, the heat treatment conditions for the specimen (I) are shown below.

Quenching; Heating temperature; 1,000℃ Heating rate; 350℃/SeC Holding time; '17sec Cooling rate; 265℃/see Tempering; Heating temperature; 500℃ Heating/holding time; 1!5sec Cooling rate; 165℃/5ec (3) Intergrain di11 determination of structure All grain sizes were measured for each of the above heat-treated specimens using the measurement method according to the JIS %j rating. II) 11 The results are expressed in Table 2 using particle size No. 119.

Table 2, specimen (I) without addition of V and V for comparison;
Microscopic photographs of the crystal grains of the specimen (ni) with 0.24% addition are shown in FIGS. 1(a) and 1(b), respectively. Both magnifications are 400x.

From the results of Experiment 1 above, heat treatment consisting of rapid heating and rapid cooling breaks the conventional wisdom that the limit was to add 0.20% V ff and make the grain size about 8 to 9. Measured crystal grain size of specimen (I), which is a non-additive material subjected to heat treatment under the same conditions, is 10.0'i. An ultra-fine grain size of 12.0, which far exceeds the
The effective interaction between addition and rapid heating/cooling is clear 1
Confirmed by

Furthermore, the present inventor compared the above experimental results of the present invention with the crystal grain size of conventional V-added heat-treated materials (electric furnace heating quenching/electric furnace heating tempering).

This is shown in Figure 2. In Figure 2, the amount of V added is plotted on the horizontal axis, and the grain size number of the crystal is plotted on the vertical axis.
FIG. 3 is a diagram in which the measurement results are plotted, and a trend characteristic curve is drawn using all the solid lines, and the plot is compared with the grain size characteristic curve regarding the amount of addition in the conventional (1) additive heat-treated material shown by the broken line. From Figure 2, it can be clearly seen that the interaction between the addition of V of 0.10% or more and the heat treatment of the present invention using rapid heating and cooling is extremely effective in making the crystal grains ultra-fine. 7 sign.

From the above results, the effectiveness of the first technical idea of the present invention has been fully demonstrated. In order to fully demonstrate how tempering by rapid heating and rapid cooling effectively contributes to increasing softening resistance,
The following experiment was conducted.

Experiment 2゜(1) Experimental method; After quenching the wire rod shown as specimen 116 (IV) in Table 1 under the same quenching conditions as in Experiment 1, the quenched wire rod 'iA'-,
B The test specimens were divided into two groups, and the test specimen group A was fully tempered by rapid heating and rapid cooling according to the present invention, and the test specimen group B was fully tempered using an electric furnace.
-B Both specimen groups each have a total tensile strength of 200 and 9f 7
mm2, and then subjected to iJf air furnace heating for 40 minutes under various temperature conditions (300-J500°C) assumed for low-temperature annealing, and then the tensile strength of each specimen was measured.

(2) Experimental results: As shown in FIG.

In Figure 3, the horizontal axis shows the temperature equivalent to low-temperature annealing, and the vertical axis shows the tensile strength. FIG. 3 is a relationship diagram showing the change in tensile strength with respect to temperature, with the broken line B indicating the characteristic III k) obtained from the measured values of .

From the above results, the effect of improving low temperature annealing softening resistance brought about by tempering by rapid heating and rapid cooling in the second technical concept of the present invention is that the tensile strength 200 Kgf / This is evidenced by the fact that the temperature (TA>) of the present invention specimen, which indicates the limit temperature for maintaining 7 nm2f, is approximately 50°C higher than the temperature (TB) of the conventional electric furnace heated and tempered specimen. Even if the wire is manufactured, it is possible to fully remove the strain after cold coiling, so it has been confirmed that the full performance of ultra-high strength steel wire can be brought out.

If the above experiment is conducted on the wire used after cold coiling, it will be possible to fully demonstrate the effects of the rapid tempering of the present invention. Since it is extremely difficult to form a straight line for measurement, measurements were made using a specimen that was not subjected to cold coiling.

Therefore, although the above experiment does not directly prove the interaction effect of dislocation energy on ① and C during cold forming, even in experiments lacking this interaction effect, the softening resistance is improved as described above. 2 has been confirmed to be significant, so it is naturally expected that cold coiling metals will bring about even greater effects, and this will be proven by the results of the coil spring reliability test described below.

The present inventor has developed a compression coil spring loaded by cold-opening a steel wire having ultra-fine crystal grains, high strength, high toughness, and aging resistance according to the present invention. However, as soon as it showed the expected performance, it was tested for accuracy. One example from a large number of experiments is shown below.

Experiment 3゜(1) Chemical composition of the wire rod used; Same as the specimen (ill) of Experiment 1 (V; 0
．． 24) Grain size number: 11.8 Wire diameter: 10. O to φ Tensile strength; 204. OK f/am2 aperture
9; Section 45 (2) Cold coil forming The above wire rod was cold-opened into the following coil spring, and in order to remove the strain caused by forming, the treatment temperature was 400°C in total in an electric furnace.
It was finished by low-temperature annealing for 0 minutes.

Example D/d = 6 (3) Coil spring performance a, τmax = 12 QKgf / = 2 stress condition, durability of 200,000 times or more, set in the above conditions γ<3X10'' Above experimental example Since the steel wire obtained by carrying out the present invention has ultra-fine crystal grains, it has high toughness and high strength despite being finished with ultra-high strength.
High 1 (1) The steel wire is extremely excellent as a steel wire for cold-formed coil springs, which requires high strength due to its tendency to deteriorate due to labor and aging, and the performance of coil springs obtained by cold-forming using this steel wire proved by.

Induction heating or direct current heating is most suitable as the rapid heating means in the present invention.

In addition, the present invention requires rapid heating to a high temperature range of 900 to 1.100°C to extremely shorten the residence time in the high temperature zone during quenching heating, and suppression of agglomeration and growth of Cr carbide during tempering heating and low temperature. In order to meet the demand for rapid heating to increase annealing softening resistance,
At least the heating rate needs to be 100°C/sec or more, and the cooling rate required to sufficiently express the rapid heating effect also needs to be 100°C/sec or more. It has been found from numerous other experiments conducted by the present inventors that the effects of V addition cannot be fully exploited at lower speeds.

Furthermore, when the amount of V added exceeds 0.50%, there is a limit to quenching by rapid heating and rapid cooling due to the relationship between the quenching temperature and residence time in the high temperature region, and as is clear from Table 2 in Experiment 1, Since the effect of addition tends to be slightly lower, in the present invention, the amount of V added -t C+, 5o%
I kept it within.

In the present invention, a hot-rolled material containing 5AE 9254 phase material, which is most suitable for spring steel material, and VffiO added in a range of 10 to 0.50% is hardened by rapid heating and rapid cooling to achieve a grain size number of 12.0. After forming ultra-fine crystals, it is tempered by rapid heating and rapid cooling to create extremely fine micro-crystalline cold formability, as well as high softening resistance during low-temperature annealing and strain relief after cold forming. The steel wire shown is what you get. This has a tensile strength of 180 Kgf
/rnm2, it has excellent cold-opening formability, and the high-strength coil springs formed in this way take full advantage of the high toughness and aging resistance brought about by the ultra-fine crystal grains. The present invention provides a cold-formed spring steel wire that makes it possible to provide an ultra-high strength spring with outstanding spring characteristics to the industry, a method for manufacturing the same, and an ultra-high strength cold-formed coil obtained using the steel wire. It makes a huge contribution as a spring.

[Brief explanation of drawings]

Figures 1 (a) and (b) are micrographs (4) of crystal grains of specimens (I) and (III) in Experiment 1, respectively.
00 times), Figure 2 is a trend characteristic curve diagram showing the relationship between the amount of V added and the grain size for a complete comparison between the present invention and the prior art, and Figure 3 is one of the tempering effects of the present invention. It is a curve diagram comparing the softening resistance during low-temperature annealing for strain relief after cold forming with that of a conventional electric furnace tempered wire. Patent applicant Hiroshi Kobayashi, Patent attorney representing Koshuha Netsuren Co., Ltd. Fig. 1 co) Sekisa Musume (1) x 40° S-shaped body i) x 400 Fig. 2 Tsuba 3 Threshold (x40min)

Claims (1)

[Claims] ■,) Weight component ratio C: 0.50 to 0.60 inches, S4.
; 1, 20-1.60%, Mfr; 0
．． 6 0 ~ o, sos. Contains Cr;'0160 to 0.80%, and ■;
0.10-0.50. %' and the remainder is h and unavoidable impurities.Wire 42 obtained by subjecting a hot rolled material to quenching and tempering heat treatment by rapid heating and rapid cooling.
A super-strength cold-formed spring steel wire characterized by ultra-fine crystal grains. 2.) The ultra-high-strength cold +ti1 formed splinter steel wire according to claim 1, characterized in that the wire rod has a crystal grain size of 10 or more. 3.) Nail i1. Component ratio C; 0.50 to 0.60 chi,
SL: 1.20-1.60, M++: 0.6
0 to 0,80 chi. Cr; Contains 0.60 to 0.80%, and V;
A hot-rolled material with total addition of 0.10 to 0.50% and the remainder consisting of h and unavoidable impurities is drawn out and then
Heating to a predetermined quenching temperature at a heating rate of 100°C/sec or more, rapidly cooling at a cooling rate of 100°C/sec or more, and then heating to a predetermined tempering temperature at a heating rate of 100°C/sec or more. An ultra-high-strength cold-formed spring steel machine characterized by high toughness and aging properties with a tensile strength of 180 I (gf/rnm2 or more) when cooled and cooled. Manufacturing method. 4) Set the predetermined temperature to 55% higher than the quenching temperature of the non-containing material.
The method for producing an ultra-high strength cold-formed spring steel wire according to claim 2, characterized in that the temperature is set at a high temperature of 0 to 100°C. 5.) The heating time for continuous heating at 100℃/3ec or more is within jOsec, and the quenching heating time including the holding time taken as necessary is within 1.11 or 30sec. = T due to ql, 1/"Quality and barrier j1111 for ultra-high strength cold-formed springs described in item 2
1 line manufacturing method. , 3. ) , , R, l, , -f component ratio C; 0.50
~060 section 2S; 1.20-1.60 section, M++
; 0.60 to 0.80 chi. Cr; 0.60 to 0.80%';
A coil spring obtained by subjecting a hot-rolled material consisting of H and unavoidable impurities to heat treatment consisting of rapid heating and rapid cooling, and cold forming, quickly loses its low 6I annealing softening resistance and has a high Ultra-high strength cold-formed coil spring with 1 durability and 1 life after aging.