JPS591631A - Manufacture of steel material - Google Patents

Abstract

PURPOSE:To obtain a steel almost free from unevenness in the components and composition and having a fine uniform structure with high productivity by hot rolling a steel having a specified C content and by subjecting it to patenting instead of spheroidizing, cold rolling and low temp. annealing. CONSTITUTION:A carbon steel or an alloy steel contg. >=0.40wt% C is hot rolled preferably at a finishing temp. above the Ar3 transformation point. The rolled material is cooled once and reheated, or it is patented by holding at a constant temp. in a lead bath, a salt bath or the like to form uniform fine lamellar pearlite. The preferred temp. is about 400-650 deg.C. The material is then cold rolled preferably at about 20-75% draft and subjected to low temp. annealing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a steel material having a fine and uniform structure.

Conventionally, the G4 method for this divine steel material was to hot-roll steel of a predetermined composition, then subject it to full spheroidizing annealing, then cold-roll it, and then subject it to low-temperature annealing.

However, in such a conventional method, spheroidizing annealing is performed, for example, heating up for 8 hours, soaking for 4 hours + slow cooling for 10 hours.
Since the heat treatment is performed for a long time under the conditions of hr (770℃→650℃), it is difficult to perform spheroidizing annealing using a continuous heat treatment furnace, and it is necessary to use a discontinuous furnace such as a batch furnace. The problem is that each coil must be heat-treated using a heat treatment method, resulting in poor productivity and variations in the spheroidization process between the inner and outer parts of the coil. It has the disadvantage that it tends to cause

This invention was made in order to eliminate the drawbacks of the above-mentioned conventional technology, and it is possible to produce steel materials such as steel strips and steel wires with small variations in composition and structure and an extremely fine and uniform carbide structure with high productivity. The purpose is to provide a manufacturing method that can be obtained with [7].

This invention applies carbon LiAt or alloy steel with a Ct interval of 0.55 to 1.0 weights by applying patenting to the edges of fully hot rolled steel, followed by cold rolling and then low temperature annealing. It is characterized by obtaining a steel material having a uniform and fine structure.

The steel to which this invention is applied has a C content of 0.55 to 1.
It is 0% by weight carbon steel or alloy steel. In this case, if the C-containing acid is less than 0.55 weight 11, the amount of ferrite produced will increase, which is undesirable, and if it is too much, by 1.0 weight, network-like carbide will be formed, which is not preferable. Therefore, the C-containing layer has a weight range of 0.55 to 1.0.

In addition to spun carbon steel, St”, Mn, Ni
, Cr.

Mo, W, Ti, V, Zr, Nb
, Ta, Cu, P, S.

1ai of Pb, Ca, Ce, 'REM etc.
t or 2 or more kinds appropriately contained, or 0. It can also be applied to A, etc., where the upper limit of S, etc. is regulated.

When hot rolling steel in this way, the rolling path IEm
It is desirable that the temperature is -F below the austenite transformation point (Ar3 transformation point). In this case, if the end-of-rolling temperature is too high, ferrite will be produced in large quantities, which is undesirable.On the other hand, if the end-of-rolling temperature is too low, a large amount of bainite will precipitate, so it is not desirable. Therefore, the final temperature during hot rolling is preferably determined by taking into account all the formation of ferrite and bainite, and more preferably from 750 to 850°C.

After this hot rolling, the rolled material is once cooled and then reheated, or patenting is applied following the hot rolling. This patenting is performed in order to obtain a constant fine lamella-pearlite structure by keeping the rolled material at a constant temperature. In this case, for constant temperature maintenance, conventionally known means such as a lead bath or a salt bath can be used, and in some cases, air patenting can also be used.

The upper limit of the constant temperature holding temperature during patenting should be determined by taking into account the temperature at which ferrite precipitates, and the lower limit by taking into account the temperature at which bainite precipitates, and more preferably 400 to 650°C. good. Further, it is desirable that the grain size of the structure obtained after constant temperature treatment is appropriately adjusted by selecting the above-mentioned treatment temperature.

Next, after the above-mentioned patenting treatment, cold rolling is performed, and the rolling rate in this case is preferably in the range of 20 to 75 inches. That is, in order to obtain uniform processing strain in cold rolling, it is preferable to set it to 2 (1 or more), and when it exceeds 75%, it is not preferable because the workability deteriorates.

After the above-mentioned cold rolling, low-temperature annealing is performed, and in this case, it is desirable to perform the annealing at a temperature equal to or lower than the heated austenite transformation point (Acm transformation point). At this time, the grain size of the structure can be changed by adjusting the low-temperature annealing temperature and time, so it is preferable to determine the low-temperature annealing temperature and time depending on the application of the steel material.

The carbide structure of the steel material obtained after such a series of treatments is fine and uniform, and it is possible to improve the structure of the product itself using this steel material, as well as to improve the shearing process of this steel material. It has the characteristics of being able to increase the life of tools used for tools, and also making the shear surface good, and has good workability when processing into mainsprings, cutlery, etc., for example. , it has the advantage that variations in hardening hardness can be made small.

Examples of the present invention will be described below along with comparative examples.

Example According to the process shown in FIG. 1, first, the C-containing layer was
Heavy steel (SK5) is melted and then hot rolled to a plate thickness of 4.
A ma+ rolled material was obtained. At this time, the rolling end temperature is 80
The temperature was kept at 0°C. Next, a part of the rolled material is cooled and then reheated, and the temperature of the other part after hot rolling is adjusted, and the temperature of the other part is adjusted to 2 to 850°C in a continuous heating furnace.
After holding for 3 minutes, a patenting treatment was performed by passing the sample through a continuous lead bath furnace maintained at temperatures of 450°C, 550°C, and 650°C for 2 minutes.

Subsequently, a rolling rate of 50 was applied to each copper strip after patenting.
% cold rolling was carried out, and the plate thickness was reduced to 2 mm.

Next, a part was subjected to low-temperature annealing at 720°C for 2 hours, and the other part was subjected to low-temperature annealing at 720°C for 10 hours. The average grain size of the carbide structure of each of the steel materials thus obtained and its dispersion were investigated, and the results are shown in Table 1. In addition, when the structure of some of the samples was examined, the results were shown in FIGS. 3 and 4.

Table 1 Comparative Example According to the process shown in Figure 2, first, the C content was 0.85.
Weight: After melting 〇 steel (SK5), it is hot-rolled to a plate thickness of 4.
A rolled material of (2) was obtained. Next, the rolled material was heated to 770°C.
After spheroidizing annealing under the conditions of X4hr, the rolling rate was 50%.
A cold-rolled material with a plate thickness of 2 was obtained by performing all of the cold rolling operations, followed by low-temperature annealing at 720° C. for 4 hours. and,
When the average grain size and the variation thereof of the carbide m weave of the thus obtained steel material were investigated, the results are shown in Table 2.

Table 2 As is clear from the results shown in Tables 1 and 2 and Figures 3 and 4, the carbide structure of the steel obtained by the present invention is considerably larger than that of the conventional spheroidizing annealed steel. It was observed that the particles were fine and uniform with little variation in particle size.

In addition, although the above Examples and Comparative Examples are explained using steel strip as an example, even when the explanation is made for wire rods, the carbide structure in the steel of the wire rod according to the present invention is considerably finer and more uniform than that of conventional ones. One thing was recognized. Good results were also obtained with alloy steel.

As explained above, according to the present invention, it is possible to obtain steel materials such as steel strips and steel wires that have small variations in composition and structure and have an extremely fine and uniform carbide structure.
It is easy to manufacture steel products using continuous equipment, which has excellent productivity, and there is no bending or bending of the steel wire when using coil material for spheroidizing annealing as in the past, and the quality is improved. 0, which has a very excellent effect of being able to obtain excellent steel materials.

[Brief explanation of drawings]

Figures 1 and 2 are explanatory diagrams showing manufacturing process 4 of steel materials in Examples and Comparative Examples of the present invention, and Figures 3 and 4 are
The figure is a photograph (400x magnification) of the microscopic ψ structure of a steel material manufactured in an example of the present invention. Patent Applicant Daido Steel Co., Ltd. Representative Patent Attorney Yutaka Kosho Figure 3 Figure 4 Procedural Amendment (Voluntary) March 18, 1980 Commissioner of the Japan Patent Office Kazuo Wakasugi 1 Indication of Case 1988 Patent 1 No. 109872 No. 2 Issue #40 Name Method of manufacturing steel materials 3 Relationship with the case of the person making the amendment Patent applicant 51lfl, -Q It”S (name) 66 Kawide, Hoshizaki-cho, Minami-ku, Nagoya, Aichi Prefecture (371 ) Daido Steel Co., Ltd. 1. The claims in lines 4 to 8 of page 1 of the specification are amended as follows: ``2. Claims (1) C content is 0.40 weight % or more of carbon steel or alloy steel, followed by patenting, then cold rolling, and then low-temperature annealing." 2. Specification No. 2 “0.55 to 1” in lines 17 to 18 of the page
．． Correct "0-fold both angles" to r O, 40-folds and above. 3. "0.55 double f-chi" on page 2, line 19 of the same page is r O,
Corrected to 40% by weight. 4. Make all corrections from page 2, line 20 to page 3, line 7 as follows. "It is not preferable because the amount of erite produced increases. Therefore, the C content should be 0.40 or more. A more desirable steel to which this invention is applied is C:
0.40 to 1.30 weight, 81: 1.0 weight or less, 1% or less, Mn: 1.5 weight or less, the balance substantially consisting of Fe, or this, Cr: 2.0 weight % or less, Mo: 1.0 weight or less, W: 1.0 weight or less,
V: 0.5 weight 5tsu, Ti: 0.5 weight% t% or less 18 or alloy steel with two or more added, other Ni
, Zr, Nb, Ta, Cu, P. 1 of S, Pb, Ca, Ce, RIM, etc.
It is an alloy steel containing a carbon dioxide or two or more species as appropriate, and upper limits of o, s, p, etc. are specified." 5. "C content is 0.85 6. Correct ``Table 1'' in line 17 of the 6th generation to ``Same as 1st - Thorn''. do. 8, page 7, lines 13 to 14 [C content length is 0.8
5 Modified appetizers - Steel (SK5) J is corrected to "steel with chemical composition shown in Table 2". 9, page 7, line 16 [770℃X 4 hr J
f [As shown in Table 2, 770°C x 4 to 6 hours
Correct to J. 10. Correct "50%" on page 7, line 17 to "45-50chi". 11. “720℃ x 4h
"r" is corrected to [also shown in the second column]. 12, page 8, line 1 [2nd Shiji J ′fcr same <
Correct to m2 clothes J. 13. The 2nd costume of the 8th Yoshi will be amended as follows.

Claims (1)

[Claims] (1) After hot rolling carbon steel or alloy steel with a C content of 0.55 to 1.0%, patenting the steel,
A method for manufacturing a steel material having a microstructure, which comprises cold rolling and then low-temperature annealing.