JPS6293343A - Non-heattreated steel wire - Google Patents

Abstract

PURPOSE:To develop a non-heattreated steel wire for bolt excellent in workability and toughness and having high strength by subjecting a steel stock containing additive components such as Nb, V, etc., to hot rolling and cooling each under specific conditions and then by wire-drawing the above. CONSTITUTION:The steel stock contain, by weight, 0.1-0.2% C, <0.35% Si, 1-2% Mn, 0.005-0.05% Nb, 0.05-0.25% V, 0.005-0.025% N, <0.020% P and <0.015% S or further containing 1 or >=2 kinds among 0.05-0.5% Ni, 0.05-0.5% Cr and 0.05-0.5% Mo is heated to 1,000-1,120 deg.C and ten hot-rolled in such a way that finish rolling temp. is 750-950 deg.C. This hot-rolled steel stock is cooled at an average cooling rate of >=5 deg.C/sec through the temp. range from 800 down to 500 deg.C to have a structure of ferrite + bainite or of ferrite + pearlite + bainite, which is subjected to wire drawing so as to manufacture the non-heattreated wire for bolt having a tensile strength as high as 90-110kgf/ mm<2>.

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to improvement of non-tempered wire rods, particularly steel for bolts. [Conventional technology] Bolts used in mechanical parts have traditionally been cold-formed from wire rods and then heat-treated to give them the required strength.
It is manufactured using the procedure 16. A typical WA manufacturing process is as follows. (Wire trA) → Softening annealing ↓ Primary wire drawing ↓ Spheroidizing annealing ↓ 11-up wire drawing ↓ Cold forming ↓ Thread rolling ↓ Quenching, baking 1 must be done - (Small Roux) This product)'L'-i horn Since the number of θ, IJ, and T are large, and the number of λ is large, an improvement is required. If the heat treatment of annealing and ashing can be omitted,
Ministry of Energy [226^ of energy 1,: not tJ,
Wire drawing can be completed in one step, and the wire size can be reduced to 11L, and the wire can be easily drawn. This J, u', f @! The applicant who proceeded with the research from point J has a tensile strength of 11J, 70~8ONyt/
mtn2) OJ, bi8T$7. t (80-90Kg)
I"/nun2>'s Pol + Kawa J1 tempered wire rod was developed, and J( was first proposed (121 Monsho 4) 9-10706
No. 3). However, with regard to the strength of Pol 1, since further improvement is required after CIJ, the Ministry of Invention et al.
/Continuous research aimed at realizing a bolt that reaches #2 1
゜Products obtained using existing technology (a) have increased strength but have lower toughness, and when subjected to a simulated tensile test (2) it is difficult to break from below the neck, and ( 2) The deformation resistance is high and the deformability is poor (the so-called "header" 1) is not good), so cold forming of Pol] is difficult and the mold life is short. However, it has not yet reached the level of practical use.

[Problems that the invention attempts to solve]

The purpose of the present invention is to overcome the current state of the technology described in (-), and to provide non-tempered steel wire rods, especially wire rods for bolts, with good processing t/l and superior toughness of 9 and 10. It's about providing something. [Means for solving the problem] The non-tempered steel wire rod of the present invention is basically C:O. 1 to 0.2%, 3i: 0.35% or less, Mn: 1°O to 2.0%, Nb: 0.005 to 0.05%, A,
l! :0.01~0.05%, N:0.005~0.
025% and V: 0.05-0.25%, P
:O, (120% or less, S: 0.015% or less, the remainder being substantially [e to (2) steel, 1000 to 11
Heating to 20℃ and finishing 1st rolling temperature is 750-950℃
The area of ε300 to 500°C is cooled at an average cold J and a speed of 5°O/sec or more to form a lai 1 ~ peinoite structure or ferrite + pearlite + baini 1 ~ structure, and further Wire is drawn to have a tensile strength of 90.
It is characterized by having 11ONgf/M2. Non-tempered steel wire rod 131 of the present invention, in addition to the above basic composition, Ni: 0.05 to 0.5%, Cr: 0°05 to
0.5% JjJ, Mo: 0.05 to 0.5% of type 1, type 2, or type 3 was added using steel, and the above-mentioned strip 1'1 lower was processed. It may be.

[For use]

The effects of the alloy components constituting the non-tempered steel wire of the present invention and reasons for limiting the composition are as follows. C: 0.1
~0.2% 1511,- to ensure 9-10T class strength
6 = 0.1% or more is required. However, if there is too much marten, the structure becomes rough and tough when cooled.
11 to 0.2%. Si: 0.35% or less 1 Used as an electrifying agent, but has a negative effect on cold formability.

[Limited to 0.35%. Mn: 1.0-2.0% Baka quenching with deoxidizing and desulfurizing effects 1) Improves 1
Ru. 131 for relatively slow cooling and large diameter wire, quenching 1
For example, a wire with a diameter of 15 mm (1.0 % or more is required. On the other hand, excessive addition of 11 old J increases the degree of segregation and decreases toughness 1) 1! Ru. Nb: 0.005-0.5%, △, fl: 0.0
1 to 0.05%, N: 0.005 to 0.025% Both of these elements have the function of refining the grains after rolling, and are used together in anticipation of a synergistic effect. By adding the above-mentioned lower limit or higher, 1:1 is added to the heat quality. /, : /Goshi, /L + Song are saturated at their upper limit of 1°V: 0.05~0.2! It is an element that forms carbides at a relatively low temperature by heating before rolling, and forms a solid solution at a relatively low temperature when cooled to 7.11. Precipitation - (Precipitation hardening. This is reduced by the addition of 0.05% culm, but it becomes saturated when it exceeds 0.25%. P: 0.020% or less, S: 0.015 % or less These impurities cause segregation and form sulfide-based inclusions, which are harmful to toughness ↑]1 and addition-1↑'I, so the above n'[ Growth should be within 1a. Ni: 0.05-0.5%, cr: o, o5-o
. 5%, MO: 0.05-0.55% Eventually -b quenching 1'l will be improved! It is an element that is
Large diameter wire +A with slow cooling rate! It may be added as appropriate when covering the structure. Diameter 15#l as described above
For 1/1 culm size, addition amount of 0.5% or less is sufficiently effective. The rolling process performed in the present invention on steel with the above-mentioned alloy components! No. 1 was adopted with great success. Heating temperature [η: 1000-1120°C In order to form a solid solution of V carbide having precipitation hardening ability during the cooling process and to sufficiently soak the steel slab, heating to 1000°C or higher is necessary. If the temperature is too high, the initial crystal grains will become coarse and fine crystal grains will not be obtained after rolling, so a heating temperature of 1120° C., which is the upper limit, is selected. Finish rolling is carried out in a non-recrystallized region with a near finish rolling temperature of 50 to 950° C., and finish rolling is carried out within this temperature range in order to obtain a fine rolled structure. Cooling rate: average 5°C/sec or more in the SOO~500°C range
During rolling and subsequent operations such as winding and focusing, the precipitation of carbonitrides (1st strip ('l IJ,, density)) will affect the strength. When passing through the above temperature range, the average cooling 11 speed is 5℃.
By rapid cooling for more than 1 second, a structure is formed, and carbonitrides are formed to form the required strength. can be received. Normally, the Beinai 1 structure is often lower in toughness than Pearlite, or according to the present invention
-Form I to Bayley (31, Thin*-°f phase weave (°
゛Because there is, ]] + lie 1 which two phases also 1, i, no I lie 1 ~ and barai! By making it a three-phase structure with -, the toughness of 1 no 1 becomes 1!7, which is 1] (). [Example] A steel having a composition shown in Table 1 was melted and a strip 1 shown in Table 2 was prepared.
'1 is the line +411 extension, which is the number of lines/i. First invention'] -1, r Straw basic alloy composition steel (test (
AA, B, C) to 1:11, direct f ¥9.0m line (A
This is a small wire with a diameter of 7.8 m.
It was made into a 10-wire H, then formed into a hexagonal pole of M8 x length BOmm, and thread-rolled to make a bolt. Finally 200℃
A bluing treatment was performed for 4 hours. On the other hand, in the second invention, that is, from steel with an alloy composition containing optionally added elements, 1 q of wire rod with a diameter of 15 # is cold drawn and made into a bolt wire rod with a diameter of 11.8 M.
Next, mold it into a Ml 2X bolt with a length of 100mm 1). Finally, it was subjected to bluing treatment in the same manner as in the first invention. For comparison, a bolt was formed from 30M440 with the same strip A'1 as in the second invention, and quenched and tempered. A tensile test was conducted on each drawn wire material, varying the ferrite crystal grain size. The results are shown in Table 3. In addition, each Pol+ was subjected to a mock tensile test. The data are shown in Table 4. 1. I C'J C [F] TO1D -TO O Dimension O "Dimension O Σ Volume U-cl15 Old No. 2 Table NO. Sample material Heating temperature Finishing temperature Cooling rate -□
-Iri- -C Rito-(℃/ fri-first-invention 'I
A 11 (1085050〃 2
A 1050 800 30 Comparative example 3
A 1150 1000 30 First invention
4 B 1050 850 20
5 C110085010 comparative example 6
C11008501 Second invention 7 D
1050 Boo 30 8
F 1050 800 50 Comparative Example 9
F 1050 800 30th
3 Table No. Test + A] 1 piece lie 1~ Tensile strength -
Crystal grain L (be L four shrines first invention 1 △ 11.5 1
05.3u 2 △ 12.0
103.7 Comparative Example 3 A
9.0 103.5 First invention /l
1111.8 107. (5” 5
C11,5109,3 comparative example 6 C1
1,59 (3,5 Second invention 7 D
11.0 103.71 8 F
11.3 107.8 Comparative Example 9
F B, 0 100.3
” 10G 9.3
106.40, 2% proof stress Elongation Restriction (Kg 'f'/mnυ-1〈%〉 94.8 15 =N 93.0 17 47 92.1 15 35 95.2 15 4.2 9B, 4 15 43 88 .7 18 50 93.1 16 43 97.0 16 42 90.2 18 46 95.0 16 48 Table 4 No. Test +4 Wedge tensile strength ++a Breaking i1
``Device (KUf/mIn2) ffj-f明I A 1(')3.?)
aSiAls?ノ 2 △ '10
2.0 Comparative example 3 A 96.3 Ministry of sewage invention / I B 105.2 Threaded part 5 C106, /1 Comparative example 6 G 97.5 Second invention 7
D 103.01/ 8 [-105,6 Comparative example 9 F 98.2 Port -I
τll 1n G 105.7 Threaded part =
15-g■Momme 1. A high-temperature steel wire mill of the present invention (1. By a well-balanced combination of alloy film h1 and processing conditions, high
A high tensile strength of 9 to 10 blades was achieved while maintaining 1] l and toughness of 121. In other words, conventional material SC
Performance equivalent to M440 hardened and tempered material can be obtained without heat refining. Therefore, this wire is most suitable for the production of por l~. In addition, it is suitable for any month.

Claims (2)

[Claims] (1) C: 0.1 to 0.2%, Si: 0.35% or less,
Mn: 1.0-2.0%, Nb: 0.005-0.05
%, Al: 0.01-0.05%, N: 0.005-0
．． 025% and V: 0.05 to 0.25%,
A steel containing P: 0.020% or less, S: 0.015% or less, and the remainder substantially consisting of Fe, is
Heating to 0°C and rolling to a finish rolling temperature of 750 to 950°C, and cooling the 800 to 500°C region at an average cooling rate of 5°C/sec or more to form a ferrite + bainite structure or ferrite + pearlite + bainite structure. As an organization,
Further wire drawing increases the tensile strength to 90 to 110 kgf/mm^
2. A non-thermal steel wire rod characterized by: (2) C: 0.1 to 0.2%, Si: 0.35% or less,
Mn: 1.0-2.0%, Nb: 0.005-0.05
%, Al: 0.01-0.05%, N: 0.005-0
．． 025% and V: 0.05-0.25% plus N
Contains one, two or three of i: 0.05-0.5%, Cr: 0.05-0.5% and Mo: 0.05-0.5%, P: 0.020 % or less, S: 0.015% or less, and the balance is substantially Fe.
Heating to 0~1120℃ and finish rolling temperature is 750~9
The material is rolled to a temperature of 50°C, cooled in the 800 to 500°C region at an average cooling rate of 5°C/second or more to form a ferrite + bainite structure or a ferrite + pearlite + bainite structure, and then wire-drawn to increase the tensile strength. 90-110kg
A non-thermal steel wire rod characterized by f/mm^2.