JPH05209220A - Production of parts made of steel - Google Patents

Abstract

PURPOSE:To produce high quality parts made of steel without intermediate and temper heat treatments by applying high velocity hot forging to a nonheat- treated steel stock, finishing the above forging at the prescribed temp., and then forming the resulting preformed body into the prescribed shape by means of warm forging at low draft. CONSTITUTION:High velocity hot forging is applied to a nonheat-treated steel stock to form it into a preformed body having a shape near to the prescribed shape. It is preferable that this steel stock has a composition containing, by weight, 0.3-0.6% C, 0.1-2.0% Si, 0.2-2.5% Mn, 0.005-0.1% Al, 0.005-0.3% N, and <=0.5% V and/or Nb as essential components, also containing Cr, Ni, Mo, W, S, Pb, Bi, Te, etc., as optional additive components, and having the balance Fe with impurities. Further, the above hot forging is done at 1100-1250 deg.C and finished at the finishing temp. where the initial crystal grain size becomes increased. By the above procedure the hardness of the preformed body can be regulated to HRC 20 to 28, and warm forging is applied to the preformed body at 600-700 deg.C at low draft to form it into the prescribed shape. By this method, the parts made of steel free from strain can be obtained while obviating the necessity of notmalizing, quench-and-temper, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving the quality of steel parts and simplifying the manufacturing process. For example, automobiles, household electric appliances, office equipment, industrial machine tool parts, agricultural machine parts, textile machines. The present invention relates to a method of manufacturing a steel part used for manufacturing various steel parts used in parts and the like.

[0002]

2. Description of the Related Art In recent years, in manufacturing various steel parts, in order to reduce the product cost, the working means is from cutting to cold or warm forging (including general plastic working in so-called cold or warm. .) Is often changed.

The forgeability of the steel material in such cold or warm forging is greatly influenced by the deformation resistance of the material, the deformability, the toughness of the tool, the wear resistance, the lubricant, etc. Without comprehensive progress in these technologies, it is difficult to completely replace the conventional main machining means, cutting.

However, in recent years, these techniques have been rapidly advanced, and cold or warm forging has been adopted for many parts.

Cold or warm forging is a processing method superior to cutting in terms of productivity, material yield, etc., and is close to precision cutting parts in terms of processing accuracy, which was the most technically difficult. Therefore, the applications are expanding rapidly.

In general, when manufacturing steel parts by cold or warm forging, a steel material such as a wire rod or a bar material is subjected to a pretreatment such as pickling and then a pretreatment such as coating and lubrication. After that, the surface condition was adjusted, and the product was cut into a state close to the product weight, and then cold or warm forging of several steps was performed.

[0007]

However, in some of the cold or warm forged products, the crystal grains may be abnormally coarsened due to the working strain accumulated during the cold or warm forging. However, this may lead to uneven strain, which sometimes causes cracking or requires normalization. It has been an issue to reduce the deterioration of quality due to the occurrence of strain and the decrease of productivity due to the necessity of normalizing.

[0008]

SUMMARY OF THE INVENTION The present invention has been conceived in view of the above-mentioned conventional problems, and does not necessarily require an intermediate heat treatment such as normalizing, and does not require quenching and tempering. It is an object of the present invention to provide a method for manufacturing a steel part that does not require heat treatment, eliminates the occurrence of uneven strain, and can improve the quality of steel parts and simplify the manufacturing process. ..

[0009]

A method of manufacturing a steel part according to the present invention is a high-speed hot forging of a non-heat treated steel material (meaning hot plastic working, which is representatively referred to as "forging"). ) Is added to finish the forging at the final temperature of the hot forging to increase the initial grain size and form a preformed body with a shape close to the prescribed shape of the steel part, and then warm forging with a low degree of workability. (Means plastic working in a warm state, and is representatively referred to as “forging” here). It is characterized in that it is formed into a predetermined shape by adding, and in an embodiment adopted as necessary. Is a non-heat treated steel material, wt%
And C: 0.3 to 0.6%, Si: 0.1 to 2.0%,
Mn: 0.2-2.5%, Al: 0.005-0.1
%, N: 0.005 to 0.3%, V: 0.5% or less, Nb: 0.5% or less as a basic component, and an optional additive component is Cr: 5 0.0% or less, N
i: 5.0% or less, Mo: 3.0% or less, W: 3.0%
One or more of the following, S: 0.03 to 0.
15%, Pb: 0.05 to 0.30%, Bi: 0.00
5 to 0.10%, Te: 0.005 to 0.10%, which may consist of the balance Fe and impurities, and is hot forged in an embodiment adopted as necessary. In the embodiment in which the temperature is set to 1100 to 1250 ° C. and also adopted as necessary, the hardness after hot forging is set to H _R C20 to 28, and is also adopted as necessary. The embodiment is characterized in that the warm forging temperature is set to 600 to 700 ° C., and means for solving the above-mentioned conventional problems with the configuration of the invention related to the method for manufacturing a steel component described above. I am trying.

In the method for manufacturing a steel part according to the present invention, C: 0.3 to 0.6% and Si: 0.1 are% by weight.
~ 2.0%, Mn: 0.2-2.5%, Al: 0.00
5 to 0.1%, N: 0.005 to 0.3%, and V:
One or two of 0.5% or less and Nb: 0.5% or less is a basic component, and an optional additive component is Cr: 5.0%.
Below, Ni: 5.0% or less, Mo: 3.0% or less, W:
One or more of 3.0% or less, S: 0.0
3 to 0.15%, Pb: 0.05 to 0.30%, Bi:
0.005-0.10%, Te: 0.005-0.10
%, A non-heat treated steel material composed of the balance Fe and impurities can be used.

In this case, C is a basic component for securing the strength, so it is desirable to set it to 0.3% or more, but if it is too much, the ductility and toughness decrease, so it is desirable to make it 0.6% or less. , Si is effective as a deoxidizing element, so it is desirable to set it to 0.1% or more, but it is desirable to set it to 2.0% or less because if it is too much, the forgeability is lowered, and Mn is a deoxidizing and desulfurizing element. It is preferable that the content be 0.2% or more because it is effective as the above and is also effective for improving the strength.
% Or less, Al is preferably 0.005% or more for deoxidation and particle size adjustment, but if it is too much, it lowers the workability, so 0.1% or less is desirable, N is preferable to be 0.005% or more because it forms a nitride to improve the toughness of the component, but if it is too much, the workability decreases, so it is preferable to make it 0.3% or less. Nb improves the toughness of parts by forming carbonitrides, but if it is too much, it increases the deformation resistance during forging, so it is desirable to make it 0.5% or less for all of Cr, Ni, Mo. , W improves the strength and toughness of non-heat treated parts, but if they are too much, they lower the workability. It is desirable that S, Pb, Bi, e it may be added in the above range so advantageously also when performing the cutting in finishing a effective element in improving the machinability.

Next, high-speed hot forging is applied to the non-heat treated steel material to complete the forging at the hot forging end temperature at which the initial crystal grain size increases, thereby preforming a shape close to the predetermined shape of the steel part. Shape into the body.

At this time, the reason why the high speed hot forging is applied to the steel material is that the hot forging end temperature can be raised by the high speed hot forging. This is because the initial crystal grain size of the preform is increased by controlling the temperature high.

In order to make the initial crystal grain size of the preformed body large, it is desirable to set the hot forging final temperature to 900 ° C. or higher. From this point of view and from the viewpoint of operation, etc. From the hot forging temperature 1100
It is more desirable to set the temperature in the range of ˜1250 ° C.

Further, the preform is made to have a shape close to the predetermined shape of the steel part in order to reduce the workability in the subsequent warm forging.

[0016] Then, it is desirable that the hardness of the preform to be the H _R C20~28 is after hot forging as described above, a sufficient strength is low hardness of the preform difficult to obtain On the contrary, if the hardness of the preform is high, the warm forgeability is deteriorated.

After the hot forging, the preformed body is formed into a predetermined shape by applying a warm forging with a low workability. The warm forging temperature at this time is the warm forgeability and the crystallinity. From the viewpoint of preventing particle coarsening, etc., 600-700 ℃
It is more desirable to set the range to.

FIGS. 1, 2 and 3 show the procedure for calculating the degree of processing in steel parts of various shapes, which is a simple compression process or a simple compression process from the preform 1a shown in FIG. 1 (a). The workability F when obtaining the steel part 1b shown in FIG. (Where, h ₀ is the height before processing, S ₀ is the cross-sectional area before processing, h ₁ is the height after processing, S ₁ is the cross-sectional area after processing), and FIG. The workability F in the case of obtaining the steel part 2b shown in FIG. 2B from the preform 2a shown in FIG. (However, S ₀ is the cross-sectional area before processing and S ₂ is the cross-sectional area of the opening after processing). Upsetting or similar processing from the preform 3a shown in FIG. The workability F when obtaining the steel part 3b shown in FIG. (However, S ₀ is the cross-sectional area before processing and S ₃ is the cross-sectional area of the processed portion after processing).

In the warm forging, which is exemplified by such a workability, it is particularly desirable that the workability F be 10% or less.

Therefore, since it is possible to form a predetermined shape by warm forging, one-step finishing is possible, and intermediate heat treatment such as normalizing can be eliminated.

In this way, by forming into a predetermined shape by warm forging, it is possible to obtain a non-heat treated and high-quality steel part without performing heat treatment such as quenching and tempering. In this case, it goes without saying that appropriate finishing may be performed.

[0022]

The method of manufacturing a steel part according to the present invention comprises:
With the above-described structure, the preform obtained by adding high-speed hot forging to a non-heat treated steel material has a large initial crystal grain size, and the preform has a shape close to a predetermined shape. Therefore, the degree of working during the subsequent warm forging is small, and intermediate heat treatment such as normalizing is not always necessary, and heat treatment such as quenching and tempering is performed. Even without them, steel parts with excellent mechanical properties can be obtained, which does not cause coarsening of crystal grains due to heat treatment, and the strength and shape accuracy of steel parts such as fatigue, compression, and tension. Is further improved.

[0023]

[Example] Using a non-heat treated steel material (as-rolled) consisting of the chemical components shown in Table 1, heated to a temperature T ₁ = 1180 ° C. in FIG. 4 by an induction heating device incorporated in a high-speed hot forging machine, Then, after performing high-speed hot forging, the cooling rate was set to 2.
It cooled, adjusting at 6 degree-C / sec, and obtained the preform.

This preform has a shape close to the finished shape of the steel part (flange companion in this embodiment), and was set so that the workability in the later warm forging was 5%. ..

Further, the hardness of the preform _H R _C20~2
It was within the range of 8.

Next, shot blasting for removing the scale during hot forging is performed on the preformed body, and then the temperature T _{2 of} FIG. 4 is 620 ° C., 650 ° C., 680 ° C.
Warm forging was performed at three different temperatures of ° C.

When the characteristics of the flange companion thus obtained were examined, the results shown in Table 2 were obtained.

[0028]

[Table 1]

[0029]

[Table 2]

As shown in Table 2, the warm forging temperature T ₂ = 6
At any of 20 ° C., 650 ° C. and 680 ° C., the grain size number is finer than 10 and shows excellent toughness, and it is possible to omit normalizing as an intermediate heat treatment It was possible to obtain a good result that a steel part having a non-heat treated property and excellent characteristics could be manufactured without requiring a heat treatment for tempering.

[0031]

EFFECTS OF THE INVENTION According to the method for manufacturing a steel part according to the present invention, the initial crystal grain size of the preform obtained by adding high speed hot forging to a non-heat treated steel material is large and ,
Since the preformed body has a shape close to the predetermined shape of the steel part, the degree of workability during the subsequent warm forging is small, and intermediate heat treatment such as normalizing is not necessarily required, and It is possible to manufacture non-heat treated steel parts with excellent mechanical properties without performing heat treatment such as quenching and tempering, and further improve the strength of steel parts such as fatigue, compression and tension. It is possible to improve the quality of steel parts and simplify the manufacturing process.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a procedure for calculating a processing degree.

FIG. 2 is an explanatory diagram showing another example of a procedure for calculating a processing degree.

FIG. 3 is an explanatory diagram showing still another example of a procedure for calculating a working ratio.

FIG. 4 is an explanatory diagram showing a temperature change during hot forging-warm forging adopted in an example of the present invention.

[Explanation of symbols]

 1a, 2a, 3a Preforms 1b, 2b, 3b Steel parts

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C22C 38/12 38/60

Claims (6)

[Claims] 1. A preform having a shape close to a predetermined shape of a steel part is obtained by applying high-speed hot forging to a non-heat treated steel material to finish forging at the hot forging end temperature at which the initial grain size increases. A method for manufacturing a steel part, which comprises forming and then forming into a predetermined shape by applying warm forging with a reduced workability. 2. A non-heat treated steel material, in% by weight, C: 0.3.
~ 0.6%, Si: 0.1-2.0%, Mn: 0.2-
2.5%, Al: 0.005-0.1%, N: 0.00
5 to 0.3%, V: 0.5% or less, Nb: 0.5
% Or less as a basic component, and the balance F
The method for manufacturing a steel part according to claim 1, which comprises e and impurities. 3. The optional additive component of the non-heat treated steel material is Cr:
5.0% or less, Ni: 5.0% or less, Mo: 3.0% or less, W: 3.0% or less, one or more,
S: 0.03 to 0.15%, Pb: 0.05 to 0.30
%, Bi: 0.005 to 0.10%, Te: 0.005
The manufacturing method of the steel component according to claim 2 selected from 0.10%. 4. The method for manufacturing a steel part according to claim 1, wherein the hot forging temperature is 1100 to 1250 ° C. 5. A hardness of the preform after hot forging H _R C
The method for manufacturing a steel part according to any one of claims 1 to 4, wherein the steel part has a size of 20 to 28. 6. The method for producing a steel part according to claim 1, wherein the warm forging temperature is 600 to 700 ° C.