JPS62196359A - Non-heattreated steel for hot forging and production thereof - Google Patents

Abstract

PURPOSE:To improve mechanism properties, particularly toughness, of the titled steel to be obtained, by limiting a cooling velocity to a specific temp. range after casting at the time of manufacturing ingots, etc., from a molten steel in which steel composition is specified. CONSTITUTION:In a process for manufacturing ingots or billets from the molten steel having a composition mentioned below, the cast steel is cooled from 1,400-1,000 deg.C at a cooling rate of >=2 deg.C/min to be formed into the titled steel. The composition of the above steel consists of, by weight, 0.1-0.6% C, 0.02-2.0% Si, 0.1-3.0% Mn, <=0.05% P, <=0.05% S, 0.001-0.3% Zr, 0.001-0.1% Al, 0.001-0.02% N, one or more kinds among 0.01-3.0% Cr, 0.01-1.0% Cu, 0.01-2.0% Ni, 0.01-1.0% Mo, 0.001-1.0% V, 0.001-0.30% Nb, and 0.001-0.30% Ti, and the balance Fe with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a non-tempered steel for hot forging and a method for producing the same.

(Conventional technology) Even in the past, many mechanical parts such as automobile parts are formed by hot forging, then subjected to tempering treatment consisting of quenching and tempering, and then subjected to mechanical processing such as cutting and grinding. Manufactured by Such thermal refining treatment is extremely useful as a heat treatment for adjusting the mechanical properties of parts to desired values, and has traditionally been considered an essential treatment.

However, in today's situation where there is a strong demand for streamlining production lines and improving productivity, there are
There are many points that should be improved in the conventional manufacturing line form from the viewpoints of (1) improving productivity by preventing quench cracking during quenching, and (2) improving productivity by preventing deformation during quenching.

As a means to solve these current problems in the conventional technology at once, it is possible to omit the above-mentioned tempering treatment, and for this purpose, precipitation strengthening elements such as v are added to refine the structure and strengthen the precipitation. Various types of so-called non-thermal forging steels have been proposed that utilize the above-mentioned methods and have the required properties as-forged.

For example, in Japanese Patent Publication No. 60-45250, polygonal ferrite is formed in austenite grains by cooling the formed part at a rate of 0°7°C/sec or less over a temperature range of 1000°C to 550°C after hot forging. It is disclosed that the material is dispersed in a large amount and has a substantially fine-grained structure.

JP-A No. 59-100256 utilizes the coarsening suppressing effect of Teno Ti in the medium carbon 211 SR region, and
It is proposed to limit the i/N ratio.

JP-A-60-103161 discloses that C: 0.05 to 0.
Cr4Mn=2.20-5.9 within the range of 15%
It is disclosed to adjust to 0.

In this way, in the past, by adjusting the composition and structure of the steel, it was possible to create a non-temperature treatment that utilizes the precipitation hardening of compounds such as V and Nb during cooling after hot forging. They had obtained steel parts.

However, these conventional non-tempered steel parts have inferior toughness compared to conventional hot-forged steel parts, so they have not been put to practical use in a limited number of parts where toughness is not required. However, it has been impossible to put it into practical use in important parts that require high strength and toughness.

In particular, in order to reduce the load during processing for relatively large hot forged parts, it is necessary to heat the steel material to a temperature of 1200°C or higher.
Even if grain-refining elements such as V, Nb, and Ti are added to refine the structure, most of the compounds of these elements decompose into solid solution during high-temperature heating prior to forging, and the fine grains The chemical effect also disappears. For this reason, in order to take advantage of grain refinement by refining elements, it is necessary to devise heat treatment after vigorous hot forging, and in the end, achieving high strength and high toughness is expensive and cannot be achieved with conventional technology. It was extremely difficult.

(Problems to be Solved by the Invention) Thus, an object of the present invention is to provide a non-tempered steel for hot forging, particularly for hot forging of large parts, and its production, which eliminates the drawbacks of the prior art as described above. The purpose is to provide a method.

(Means for solving the problem) In order to achieve the above object, the present inventors conducted various studies and found that there was a solution from a completely different perspective from the conventional method, and completed the present invention. I let it happen.

In other words, the conventional method of preventing austenite structure coarsening based on the effect of inhibiting austenite grain growth by dispersing carbonitrides cannot fully demonstrate its effect at temperatures such as 1200 to 1300°C such as in hot forging. This is because when heating to a high temperature, carbonitrides completely decompose (decompose and form a solid solution in austenite), so that the effect of correcting the growth I of austenite grains is completely lost.

Therefore, in order to achieve the object of the present invention, it is necessary to use a compound that does not decompose into solid solution even under heated conditions. Such compounds include MnS, TiN -, ZrN
-There are nonmetallic inclusions such as Alz03.5ift. By the way, 8Q, which is a conventional austenite refining compound,
The decomposition temperature of N is 1100°C.

However, these nonmetallic inclusions are not the same as the conventional 'J1?
In method i, the distribution is coarse and sparse, and as it is, it is not in a state where it can effectively inhibit crystal grain growth. Furthermore, in the past, it has generally been desired to reduce the number of nonmetallic inclusions as much as possible, and there has been no idea of actively utilizing them.

After conducting various experiments, we found that by using a steelmaking raw material containing Zr, the sulfides in the steel became extremely fine, out of the nonmetallic inclusions that were previously coarse and sparsely distributed. It was found that not only the oxides in the steel became dispersed, but also the oxides in the steel became extremely finely dispersed.

Due to the effect of such Zr addition, finely dispersed sulfides,
It is thought that the presence of oxides suppresses the coarsening of austenite crystal grains during high-temperature heating before hot forging. On the other hand, since these nonmetallic inclusions do not decompose even at such high temperatures, grain growth of austenite grains in the high temperature region after forging is suppressed, and at the same time, many finely dispersed inclusions act as transformation nuclei. These effects combine to refine the final structure of the forged material, improving the toughness of the steel.

Furthermore, by finely dispersing sulfides and oxides, other inclusions in the steel are also finely dispersed, and the toughness of the steel is further improved.

Therefore, the gist of the present invention is, in weight %, C: 0.1 to 0.6%, Si: 0.02 to 2.0
%, Mn: 0.1-3.0%, P: 0.05%
Below, S: 0.05% or less, Zr: 0.00
1-0.3%, Al: 0.001-O11%
, N: 0.001 to 0.02%, and Cr: 0. O1-3.0%, Cu: 0.01-1.
0%, Ni: 0°01-2.0%, Mo: Q, Ql-1
, 0%, V: o, oot~1.0%, Nb: 0.00
1 to 0.3% and Tj: 0.001 to 0.3%, and further contains a total of 0.001 to 0.5% of rare earth elements and/or S: 0.05 ~0.5%, l”b:Q, 005~0.
59A.

Ca: 0.001-0.05%, Te: 0.001-0
．． 2%, Sago.

01-0.5%, and Bi: 0.01-0.5% 1
It is a non-thermal steel for hot forging, which contains one or more types of iron, and the remainder is Fe and unavoidable impurities.

In addition, in another aspect, the gist of the present invention is to
In ffl amount%, C: 0.1-0.6%, Si: 0.02-2.0
%, Mn: 0.1-3.0%, P: 0.05%
Below, ・S: 0.05% or less, Zr: 0.0
01-0.3%, Al: 0.001-0.1
%, N: 0.001 to 0.02%,
and 'Cr: 0.01-3.0%, Cu: 0.01-1
．． 0%, Ni: 0°01~2.0%, Mo: 0.01~
1.0%, V: 0. OQl ~ 1,0%, Nb:Q, 0
01-0.3% and Ti: 0.001-0.3% 1
0.001 to 0.5% in total of rare earth elements, and/or S: 0.05 to o, s%, Pb: 0.005 to o, s%
, Ca: 0.001~0.05%, Te: 0.001~
0.2%, Se: 0.01-0.5%, and Bi: 0
．． In the process of manufacturing steel ingots or slabs from molten steel, steel containing one or more of 01 to 0.5% and the balance consisting of Pe and unavoidable impurities is heated to 1400 to 1000°C after casting.
This is a method for producing non-tempered steel for hot forging, which comprises cooling at a cooling rate of 2° C./min or more, preferably at a cooling rate of 5 to b.

Here, "manufacturing steel ingots or billets" includes both methods such as ingot-forming and continuous casting. However, the effects of the present invention are particularly exhibited when the agglomeration method is used. When using continuous casting method,
This is because the cooling rate is often restricted by other operating conditions.

Thus, in the present invention, by making the nonmetallic inclusions as described above fine and uniformly dispersing them in the matrix, the growth of crystal grains is inhibited and the intended purpose is achieved. These inclusions are generated in molten steel and in high-temperature austenite during the solidification process, so by rapidly cooling the temperature range in which these inclusions form and precipitate, the inclusions are formed and precipitated in a uniform and fine manner.

In the present invention, there are no particular restrictions on the type, amount, or dispersion form of nonmetallic inclusions, but it is sufficient that the type and amount of nonmetallic inclusions are the same as those actually contained in ordinary steel compositions. The idea is that the degree of dispersion obtained when cooling as defined in the present invention is performed is sufficient.

However, particularly effective nonmetallic inclusions include MnS, ZrN
, TiN, the amount of which is Mn: 0.6 to 2.5
Weight%, Zr: 0.005-0.03% by weight, Ti:
The effect is significant in the range of 0.005 to 0.03% by weight.

Therefore, according to the present invention, by controlling the precipitation and dispersion of nonmetallic inclusions during solidification of the molten metal, it is possible to prevent the growth and coarsening of austenite grains during heating before hot forging and after hot forging.

In this way, the idea of suppressing the cooling rate immediately after casting is not mentioned at all in the prior art mentioned above.
Furthermore, its effect of preventing the growth and coarsening of austenite grains after hot forging due to inclusions is a matter that has not been known in the past.

In particular, in the present invention, the heating temperature during hot forging is 1200
It is particularly effective in manufacturing relatively large hot forged parts at temperatures as high as ~1300°C, for example, parts weighing 1 kg or more.

(Function) Next, the reason why the carbon content and cooling conditions are limited as described above in the present invention will be explained in detail.

C: If C exceeds 0.6%, the toughness will deteriorate and cause the same poor toughness problem as conventional hot forging non-thermal steel, so 0.6
The upper limit was %. Also, if it is less than 0.15, it will not be possible to obtain the required strength as a mechanical structural component, so 0.1%
was set as the lower limit.

Note that hot forged parts are often used after induction hardening, and in this case, Cff1 must be 0.25% or more to obtain a sufficient induction hardening effect;
If it exceeds 0.2%, quench cracking may occur.
It is preferably 5 to 0.55%.

Si: Si is a very effective element for ensuring strength, but
If it exceeds 2%, the ferrite base becomes brittle and the toughness deteriorates significantly, so the upper limit is set to 2%, preferably 1.5%. Also, what about Si? 8 It is used as an effective element for deoxidizing steel,
If the content is less than 0.02%, deoxidation will be insufficient and the composition, texture, and properties of the steel will become unstable, so the lower limit is set at 0.02%.
%, preferably 0.05%.

Mn = Mn is an extremely useful element with a large toughening effect, and 0
．． Addition of 1% or more can be effective.

If the content is less than 0.3%, hot working cracks may occur, so the lower limit is 0.1% or more, preferably 0.3%.
% or more. If the Mn content exceeds 2.0%, if the size of the hot forged part is small and the cooling rate after hot forging is relatively high, bainite will be mixed instead of a uniform ferrite pearlite Mi texture. Become. Content is 3
%, an abnormally coarse U-weave that deteriorates the toughness will occur.

Therefore, the upper limit is set to 3% or less, preferably 2% or less.

P, S, N: P, S, and N all deteriorate toughness, and if the upper limits of their respective limited ranges are exceeded, it becomes difficult to obtain superior toughness to conventional non-tempered steel for hot forging. Therefore, p: 0
．． 0.05% or less, S: 0.05% or less, N: 0.00
It was set at 1 to 0.02%. It is preferable to keep these elements in very small amounts, but in order to improve machinability, Si
may be contained above the upper limit.

Zr: If the Zr content is kept to a very small amount by treatment with an additive containing Zr, inclusions will be dispersed very uniformly and finely, improving the toughness after hot forging. However, the effect of improving toughness is recognized even in extremely fine particles whose content cannot be quantitatively analyzed using current analytical methods.However, the lower limit value was set as o, ooi%.As the Zr content increases, the above-mentioned In addition to the effect of fine and uniform dispersion of inclusions, the formation and precipitation of very fine Zr compounds further effectively refines the structure and improves toughness after hot forging.

The Zr compound at this time also has the effect of promoting recrystallization of austenite crystals and suppressing subsequent coarsening of crystal grains when forging is performed at a temperature of 1100° C. or higher, for example. In this case, if the Zr content exceeds 0.3%, the toughness deteriorates, so the upper limit was set to 0.3%.

Al: 8Q is a very useful element as a deoxidizing element, and if the content is less than 0.001%, problems such as bubbles and surface flaws are likely to occur. In addition, if it exceeds 0.1%, hot processing cracks are likely to occur, so the lower limit value should be set to o.
, ooi%, and the upper limit was set to 0°1%.

Cr-CuSN1% MOLV% Nb1Ti: All of these elements are effective in changing the structure after hot forging into a fine ferrite/pearlite &lI weave to improve strength and toughness, and at least one or two of these elements are effective. or more is added. In order to realize this toughening effect,
Since Cr, Cu, Nl, and Mo need to be at least 0.01%, and V, Nb, and Ti need to be at least 0°.001%, these were set as the lower limits. Also, Cr 3
．． 0%, Cu 1.0%, Ni 2.0%, Mo 1.
If it exceeds 0%, the structure after hot forging will have a thick toughness (l
On the other hand, Vl, 0%, )lb
If the content exceeds 0.3% and 3% of TiO, the ferrite/pearlite structure will become extremely brittle and the toughness will deteriorate, so these were set as the respective upper limit values.

Therefore, in the present invention, Cr: 0.01 to 3°0
%, Cu O, 01-1.0%, Ni: 0.01-2.
0%, Mo: 0.01-1.0%, V: O, OOl ~
1.0%, Nb: 0.001-0.3%, T turtle: 0.
001 to 0.3%.

Rare earth elements: In the case of hot forging using high temperature heating, the toughness can be greatly improved by adding rare earth elements in particular.

This improvement effect is even greater in Zr-treated steel, and the effect is observed when the content of hto exceeds 0.01%. Even if the amount of rare earth elements added exceeds 0.5%, the improvement effect is saturated, so the upper limit was set at 0.5%.

Machinability improving element: When it is required to improve machinability, S % P
One or two of b, Ca, Te, Se, Bi
It is effective to add more than one species. S: 0.05%, Pb:
0.005%, Ca: 0.001%, Te: 0.001
%, Se: 0.01%, and Bi: 0.01% are the minimum contained jets that work effectively, so these were set as the lower limit values. S: 0.5%, Pb: 0°5%, Ca: 0.05
%, Te: 0.2%, Se: 0.5%, Bi: 0°5%
Even if the content exceeds the above, the effect of improving the 711 resistance will be saturated, and the toughness will actually deteriorate significantly, so these are set as the upper limit values.

The present invention relates to a non-thermal steel for hot forging having the above-mentioned steel composition, but in order to maximize the effect of Zr addition in the present invention, it is necessary to
Preferably, the cooling rate is 2°C/min or more per 100°C. When the cooling rate is greater than 2℃/min, 2℃
sulfides formed for cooling rates less than /min,
Coagulation and coarsening of oxides and nitrides no longer occurs, and these inclusions become uniformly and finely dispersed. In particular, Z
Coagulation and coarsening of inclusions involving r-compounds begins to occur at a cooling rate lower than 5°C/min and becomes noticeable when the cooling rate is lower than 2°C/min. As a result, the toughness is significantly reduced.
The lower limit of the cooling rate was set to 2°C/min, preferably 5°C/min. In terms of finely uniform dispersion of inclusions and compounds, the higher the cooling rate, the more effective it is, but this increases the likelihood of problems such as surface cracking, so set the cooling rate as high as possible within the range that can avoid problems. This is desirable.

Generally, the upper limit is 15°C/min.

As described above, according to the present invention, after casting 1400 to 100
The cooling rate in the temperature range between 0°C and 2°C/min or more, preferably 5 to 00°C has a very large effect on the size and distribution of sulfides and nitrides, and has a significant impact on the segregation of The present invention takes advantage of the fact that the hot forged structure in the high temperature range is significantly changed by inclusions, and if the inclusions are dispersed as finely and uniformly as possible, the toughness after hot forging is improved. From 1ooo℃
It has been found that by increasing the cooling rate until , sulfides, oxides, and nitrides are uniformly and finely dispersed, and the improvement in toughness becomes even more remarkable. In particular, in Zr-treated steel, fine and uniform dispersion of sulfides and oxides becomes remarkable, and Zr
In r-containing steel, the effect of setting the cooling rate after casting to 2° C./min or more is remarkable, such as suppressing agglomeration and coarsening of Zr compounds.

As mentioned above, the cooling rate should be adjusted from casting to 1000'c, but in reality it is difficult to measure the cooling rate from casting to solidification, and cooling should be done in a straight line after solidification. Therefore, the cooling rate can be easily extrapolated, and since it can be easily measured between 1400 and 100° C., this temperature range was set as the target range for numerically limiting the cooling rate.

Note that, if desired, the amount and type of nonmetallic inclusions can be adjusted in advance by, for example, adjusting the degree of deoxidation, or by other means already well known to those skilled in the art.

゛ The thus obtained hot forging steel according to the present invention is generally heated to 1200 to 1300°C, then hot forged at a finishing temperature of 1050°C or higher, allowed to cool, and then optionally machined. , it becomes a non-heat-refined product. There is no restriction on the hot forging at this time, and it may be a conventional one, or a conventional austenite a-refining treatment may be performed after this hot forging.

Next, the present invention will be explained in more detail by way of examples.

Example 1 200 kg of steel having the chemical composition shown in Table 1 was melted in a low-frequency induction furnace, and after casting, it was cut out of a mold and cooled intermittently to a temperature between 1400 and 1000°C. 5.2℃/
The resulting steel ingot was forged into a square bar with a side of 80 mm and used as a material for the next hot forging experiment.

After heating this square bar with side 80+mm to 1250℃, 1
After hot forging into a square bar with a side of 30 mm at a forging finish temperature of 100°C, it was allowed to cool naturally.

JIS from the center of the above simulation hot forged material
Tensile test piece No. 14A (diameter of flat part 10111111
) and JISa Charpy test specimens were prepared and their mechanical properties were investigated.

The obtained temporalities are summarized in Table 2.

Table 2 (Continued on next page) (Continued from Table 2) As shown in Table 2, steel code Nos. 1 to 6 are based on the effect of CL, and steel code No. 1 has a strength of 60 kgf/opening. 2
It is not fit for purpose because it has not reached the target. Copper 1-6 has an impact absorption energy of less than 5 kgf-n+/cn1 and lacks toughness.

Steel symbols 7 to 11 show the effects of 5ilil, steel symbol N17 lacks hardness, and steel symbol 11 lacks toughness.

Steel symbols m12 to m15 show the effect of MnFl, and steel symbol 15 lacks toughness.

Steel symbols 11kl16 to 17 show the effect of Pi, and it can be seen that the lower the PWk, the better the toughness, especially the toughness at low temperatures.

Steel symbols 11118 to 19 are Cu, Ni, Cr,
This is an example of a Mo complex addition system.

Steel symbols 1b20 to 22 show the effect of Cr.

Steel code 111Q22 has a coarse structure containing bainite and has deteriorated toughness.

Steel symbols 23 and 24 show the effect of Mo, and in steel symbol 24, the coarsening and non-uniformity of the structure is noticeable and the toughness is not good.

Steel symbols 25 to 27 are based on the effects of Ti, Nb, and V, and when these elements are contained in large amounts exceeding the upper limit, only the toughness deteriorates significantly without increasing the strength.

Looking at the effect of Zr on Steel Symbol 4 and Steel Symbols NQ28 to NQ33, the effect of Zr addition is clear since Steel Symbol 4 has significantly improved toughness compared to Steel Symbol 28. When the steel code becomes 33, the strength increases, but the toughness greatly deteriorates.

Steel symbol grades 34 to 37 are based on the effect of sl, and steel symbols 11 & 137 are not practical because their toughness is greatly reduced.

Steel symbol numbers 38 to 42 show the effect of Pb stars,
Steel symbol VkL38 had almost the same machinability, particularly drill perforability, as steel symbol 隘4, but there was a strong influence on the drill perforability of steel symbol 隘39, and steel symbol N14
When it becomes 0, there is a significant improvement in turning performance.

Steel symbols 43 to 46 are based on the effect of Te content,
The machinability can be improved by adding Te, and the decrease in toughness is very small, and even steel symbol Kan 46 has practical characteristics.

Steel code 11h47-49 shows the effect of Se and Bi, and steel code N150 shows the effect of combined addition of Ca-3-Te, and in both cases the deterioration in toughness is small.

Steel codes 1 and 51 to 52 are based on the effects of rare earth element inclusion, and even a small amount of rare earth elements can change the toughness.

Class symbols 11m53 to 55 look at the effects of the addition of Ti, Nb, and V. When compared with class symbols Kan 25 to 27, when these elements are added near the upper limit, the strength increases markedly and vE2o decreases. 5 kg-++/cm”.

Example 2 Steel having the components shown in Table 3 was melted in a converter on an actual production line, and this molten steel was cast into a mold having the cross-sectional dimensions shown in Table 4.

These steel ingots of various sizes were cut out at 1400°C, and the surface l and quality of the steel ingots were measured until the temperature reached 1000°C.

At the same time, 30O of molten steel with the same charge as the steel in Table 3
It was cast into a continuous forged slab with a cross section of Ll+wX400 ms+. At this time, the surface temperature of the slab was measured at various positions in the casting machine to determine the cooling status for reference.

Table 4 shows the cooling rates of these steel ingots or slabs.

These steel ingots or slabs were rolled into steel bars with a diameter of 1300 mm, then hot forged in the same manner as in Example 1, and the mechanical properties of the final products were examined. The results are shown in Table 5.

The cooling rate for symbol 2 is less than 2°C/min compared to symbols A, 8, and 8, and the Charpy impact recovery energy is significantly lower.

The value of the symbol ``ha'' is close to that of the ``habo'' symbol ``ha''.

Claims (8)

[Claims] (1) In weight%, C: 0.1-0.6%, Si: 0.02-2.0%, M
n: 0.1-3.0%, P: 0.05% or less, S: 0.
05% or less, Zr: 0.001 to 0.3%, Al: 0.
001-0.1%, N: 0.001-0.02%, further Cr: 0.01-3.0%, Cu: 0.01-1.0%
, Ni: 001-2.0%, Mo: 0.01-1.0%
, V: 0.001-1.0%, Nb: 0.001-0.
30% and Ti: 0.001 to 0.30%, and the remainder is Fe and unavoidable impurities. (2) In weight%, C: 0.1-0.6%, Si: 0.02-2.0%, M
n: 0.1-3.0%, P: 0.05% or less, S: 0.
05% or less, Zr: 0.001 to 0.3%, Al: 0.
001-0.1%, N: 0.001-0.02%, and Cr: 0.01-3.0%, Cu: 0.01-1.0%
, Ni: 0.01-2.0%, Mo: 0.01-1.0
%, V: 0.001-1.0%, Nb: 0.001-0
．． 30% and one or more of Ti: 0.001-0.30%, further S: 0.05-0.5%, Pb: 0.005-0.5%
, Ca: 0.001~0.05%, Te: 0.001~
0.2%, Se: 0.01-0.5%, and Bi: 0
．． A non-thermal steel for hot forging, containing one or more of 01 to 0.5%, with the balance being Fe and unavoidable impurities. (3) In weight%, C: 0.1-0.6%, Si: 0.02-2.0%, M
n: 0.1-3.0%, P: 0.05% or less, S: 0.
05% or less, Zr: 0.001 to 0.3%, Al: 0.
001-0.1%, N: 0.001-0.02%, and Cr: 0.01-3.0%, Cu: 0.01-1.0%
, Ni: 0.01-2.0%, Mo: 0.01-1.0
%, V: 0.001-1.0%, Nb: 0.001-0
．． 30% and Ti: 0.001 to 0.30%, and further contains rare earth elements in a total of 0.001 to 0.5%, the balance being F.
Non-thermal steel for hot forging consisting of e and inevitable impurities. (4) In weight%, C: 0.1-0.6%, Si: 0.02-2.0%, M
n: 0.1-3.0%, P: 0.05% or less, S: 0.
05% or less, Zr: 0.001 to 0.3%, Al: 0.
001-0.1%, N: 0.001-0.02%, and Cr: 0.01-3.0%, Cu: 0.01-1.0%
, Ni: 0.01-2.0%, Mo: 0.01-1.0
%, V: 0.001-1.0%, Nb: 0.001-0
．． 30% and Ti: 0.001 to 0.30%, and further contains a total of 0.001 to 0.5% of rare earth elements and S: 0.
05-0.5%, Pb: 0.005-0.5%, Ca:
0.001-0.05%, Te: 0.001-0.2%
, Se: 0.01~0.5%, and Bi: 0.01~
Non-thermal steel for hot forging, containing 0.5% of one or more kinds, with the balance being Fe and unavoidable impurities. (5) In weight%, C: 0.1-0.6%, Si: 0.02-2.0%, M
n: 0.1-3.0%, P: 0.05% or less, S: 0.
05% or less, Zr: 0.001 to 0.3%, Al: 0.
001-0.1%, N: 0.001-0.02%, further Cr: 0.01-3.0%, Cu: 0.01-1.0%
, Ni: 0.01-2.0%, Mo: 0.01-1.0
%, V: 0.001-1.0%, Nb: 0.001-0
．． In the process of producing steel ingots or slabs from molten steel, steel containing one or more of 30% and 0.001 to 0.30% Ti, with the balance consisting of Fe and inevitable impurities. , 1400~1000℃ after casting
A method for producing non-tempered steel for hot forging, comprising cooling at a cooling rate of 2° C./min or more. (6) In weight%, C: 0.1-0.6%, Si: 0.02-2.0%, M
n: 0.1-3.0%, P: 0.05% or less, S: 0.
05% or less, Zr: 0.001 to 0.3%, Al: 0.
001-0.1%, N: 0.001-0.02%, and Cr: 0.01-3.0%, Cu: 0.01-1.0%
, Ni: 0.01-2.0%, Mo: 0.01-1.0
%, V: 0.001-1.0%, Nb: 0.001-0
．． 30% and one or more of Ti: 0.001-0.30%, further S: 0.05-0.5%, Pb: 0.005-0.5%
, Ca: 0.001~0.05%, Te: 0.001~
0.2%, Se: 0.01-0.5%, and Bi: 0
．． In the process of manufacturing steel ingots or slabs from molten steel, steel containing one or more of 01 to 0.5% and the balance consisting of Fe and unavoidable impurities is heated to 1400 to 1000°C after casting.
A method for producing non-tempered steel for hot forging, comprising cooling at a cooling rate of 2° C./min or more. (7) In weight%, C: 0.1-0.6%, Si: 0.02-2.0%, M
n: 0.1-3.0%, P: 0.05% or less, S: 0.
05% or less, Zr: 0.001 to 0.3%, Al: 0.
001-0.1%, N: 0.001-0.02%, and Cr: 0.01-3.0%, Cu: 0.01-1.0%
, Ni: 0.01-2.0%, Mo: 0.01-1.0
%, V: 0.001-1.0%, Nb: 0.001-0
．． 30% and Ti: 0.001 to 0.30%, and further contains rare earth elements in a total of 0.001 to 0.5%, the balance being F.
In the process of manufacturing steel ingots or slabs from molten steel, steel having a composition consisting of E and unavoidable impurities is heated at 1400 to 1000°C after casting.
A method for producing non-tempered steel for hot forging, comprising cooling at a cooling rate of 2° C./min or more. (8) In weight%, C: 0.1-0.6%, Si: 0.02-2.0%, M
n: 0.1-3.0%, P: 0.05% or less, S: 0.
05% or less, Zr: 0.001 to 0.3%, Al: 0.
001-0.1%, N: 0.001-0.02%, and Cr: 0.01-3.0%, Cu: 0.01-1.0%
, Ni: 0.01-2.0%, Mo: 0.01-1.0
%, V: 0.001-1.0%, Nb: 0.001-0
．． 30% and Ti: 0.001 to 0.30%, and further contains a total of 0.001 to 0.5% of rare earth elements and S: 0.
05-0.5%, Pb: 0.005-0.5%, Ca:
0.001-0.05%, Te: 0.001-0.2%
, Se: 0.01~0.5%, and Bi: 0.01~
In the process of manufacturing steel ingots or slabs from molten steel, steel containing 0.5% of one or more of two or more of the following, with the balance consisting of Fe and unavoidable impurities, is heated to 1400 to 1000°C after casting.
A method for producing non-tempered steel for hot forging, comprising cooling at a cooling rate of 2° C./min or more.