DE2165105B2 - Process for the production of ball head bolts - Google Patents

Description

1. First method According to the second method, the ball

65 head bolts with the exception of the spherical surface before the anti-carburization treatment

A low-alloy steel with more than 0.4O ⁰ ZoC layer can be given, for example a copper is used as the starting material for the ball-head pin coating or some other equivalent means, and

3 '4

After the case hardening, these different surface load conditions, for example layers that were thrown from the carburization protection treatment, complicated impact structures from several directions, completely removed, vibrations, etc., must be applied. These operations increase the manufacturing high fatigue resistance is granted,
costs for the ball head bolt. In addition, the invention relates to a method for special care to ensure that the production of a ball head bolt, in which as an off ball head bolt due to the iy. the penetrating material is a low carbon steel or a hydrogen gas used by the acid deformation properties required to remove the low carbon alloy with excellent carbon anti-carburization coatings; in addition, it stains, does not become brittle. io is a comparison with this starting material

In the case of third known processes, the cold to the known carburizing heat treatment can be easily deformed, case hardening, etc. fairly light carburizing heat treatment applied, be performed; However, if the one with a ball-headed bolt, the thread provided part of the ball head bolt by the same compared to the known ball head bolt the high-frequency heating is remunerated, the 15 or even better characteristic properties Has the tip or the head of the screw bolt faster.

heated than the rest of the bolt, so that the process characterized by the claims

not evenly tempered entire bolts. Remedial measure for the production of a spherical head-um To remedy this disadvantage, the double bolt is with regard to the heat treatment space distance between the Hoda frequency induction process easier and simpler than the well-known vertical coil and the bolt in general, and it can be compared to the well-known enlarged the usual status, which is why a procedure with a shorter procedure time which have such an unusually large distance on ball head bolts with the same or better self-pointing Make a multi-shaft high frequency induction coil.

times as much electrical energy as that coil is needed. According to the invention, a hollow is required to manufacture a coil that has a normal coil spacing. In addition, the shank part of the ball-head bolt, which is low in carbon or a low-carbon steel bolt, is hardened by the case hardening and has a carbon content of G, 12 with such a high surface hardness that the form- up to 0.23 ⁰ Zo (for example JIS S-15C, S-20C, ductility or ductility or toughness noticeably reduced 30 SNCM-21-26, SCM-21-23) and is at rings. Can be processed excellently at room temperature;

As things stand, the ball head bolt should then be made of this starting material in accordance with the following advantageous the following process steps are formed and heat-wise: treated.

35 The starting material is shaped as a ball head bolt and the hole surface of this ball head

1. Since the ball surface of the ball head bolt has a certain case hardening treatment continuously irregular turning and sliding granted; then the remuneration is paid in the usual way. or is subjected to sliding movements, currency heat treatment carried out and finally When it is under a vibrating load, only the spherical part of the ball head bolt should be attached Surface hardness have a hardness number by means of high frequency induction heat treatment is higher than 60 on the Rockwell Scale, hardens or case-hardened.

and a sufficient wear resistance. This shows the metallic structure of the upper. In addition, the spherical head surface layer should be made of martensite and the metallic bolt through a diffusion treatment of the 45 structure of the ball interior made of sorbitol, troostite and Surface carbon of the ball head stud formed ferrite, while the surface layer of the be made sufficiently malleable. Shank part and the threaded bolt part made of sorbitol

and its inner part made of sorbitol, troostite and one

2. In any case, it should be avoided that small amounts of ferrite are formed.

the screw bolt and its interior unequal 50 Abbreviations used for the individual Hard are what steels called decarburization are at the end of the description or carburization is the case. In addition explained.

The invention will be described in the following with reference to the

elastic extensibility, a sufficient drawing explained in more detail. This shows in
have high yield strength and tensile strength. 55 Fig. 1 is a temperature-time diagram of the heat.

and a corresponding stretch resistance F i g. 2 is a temperature time diagram according to FIG

to have. In particular, the shaft part of the first known method should

Ball head bolt has a high resistance to 6 «F i g. 3 is a temperature time diagram according to FIG Bending stress and high fatigue second known method,

or alternating strength can be granted. F i g. 4 is a temperature time diagram according to FIG

third known method,

5a schematically shows a hollow ball head bolt

The invention is therefore based on the object. 65 and a test device for

the above-mentioned disadvantages of the known ball F i g. 5 b plotted in a diagram

to eliminate the head bolt and to develop a method of searching results from being wound by means of the test device, due to the load tests carried out on the ball head bolt, although it measured Fig. 5a,

where the bending stress exerted on the central part of the sphere is greater than that at the center of the sphere the flexural deflection that has taken place is applied,

F i g. 5 c shows a diagram according to FIG. 5 b, in which, however, the ordinate corresponds to the absorption energy,

6 shows the hardness distribution in the hardened layer of the spherical part of the ball head bolt,

F i g. 7 the work of deformation or the deformation

17 shows the fine structure of the inner part of the shaft and the screw bolt of the ball head bolt after applying the known third heat treatment process, Ferrite + troostite + a small amount of martensite, magnification four hundred times.

A case-hardening steel, for example, JIS · SCM-21. with a salary

deformation resistance, plotted over the deformation from 0.13 to 0.18 ° / »C, 015 to 0.35 ° ο Si, 0.60 to deformation ratio, where K ₁ or ω denotes the deformation 0.85 ⁰ ZoMn, 0.9 to 1.2 ° Ό Cr, less than 0.30 ⁰ ZoCr, - - - less than 0.30 ⁰ ZoNi and 0.15 to 0.30 «/ oMo, ver

turns. This raw material is heat treated

resistance or the work of deformation of the ball head bolt material (JIS · SCM-21) according to the invention, while in contrast to Ver '' d Vfidd b

delt to create spherical carbide and im

equals K ₁ ' or ω' the deformation resistance or 15 state of a cross-sectionally round rod or

a coiled or coiled round rod. The coiled round rod is first formed at room temperature into a hollow ball head bolt, hereinafter referred to as a blank, using the manufacturing process described in Japanese Patent 15548/1969 is filled, heated to a suitable temperature between 890 and 920 ° C, which is selected according to the carbon content of the ball head bolt. In the case of one shown in FIG. 1 with the point A marked temperature of 800 ° C is passed into the Ermartensitisch, 30 hitzungsofen propane gas as enrichment gas in order to increase the carbon content of the surface layer of the blank, whereby the atmospheric gas at a dew point temperature in the range between - * 5 and -3 ⁰ C is held. The surface layer and the inner part of the screw period in which the blank is held in the bolt temperature range of the ball head bolt according to the known between 890 and 920 ° C, depends

"" according to the desired depth of carburization of the blank, for example 1 hour for a depth of about

specify the deformation work of the ball head bolt material (JISSMC-4) according to the state of the art,

8 shows a photographic image of the peen structure the spherical surface layer of the spherical head ao bolt. according to the heat treatment process according to the invention, martensitic, magnification one hundred times,

9 shows the fine structure of the inner ball part of the ball head bolt after the heat treatment process drive, sorbitol + troostite + ferrite, four hundred times magnification,

10 shows the fine structure of the spherical surface layer of the spherical head bolt according to the known one first heat treatment process, magnification one hundred times,

11 shows the fine structure of the spherical inner part, of the bolt shank part, and the surface layer and the inner part of the bolt shank part and the

0.5 mm. The enrichment gas is supplied in

first heat treatment process according to Fig. 10, sorbitol, four hundred times magnification,

Fig. 12 the fine structure of the spherical surface layer of the spherical head bolt after the application 4 ° time D, which is at the beginning of the last third of the known second and third heat treatment storage time, interrupted, whereupon the treatment process, martensite + residual austenite, one hundred blank in the Period C to D, as shown in FIG. 1 earth-fold magnification, visible, at the above-mentioned temperature the difference

13 which is subjected to photographically taken common fusion carburizing treatment, same fine structure of the ball inner part of the ball head 45 After completion of the diffusion treatment process bolt after the application of the known second (D), the blank is in the oil bath of, for example

50 ° C suddenly quenched. The inner fine structure of the blank consists of a larger amount after the above-mentioned heat treatments Martensite and a small amount of troostite and ferrite. This fine structure fully meets the requirements that of the quenched structure of the material used as the starting material according to the invention Stahls JIS SCM-21. Since about it

and the screw bolt part of the ball head bolt removed from the spherical part later by the high frequency measure of the invention as well as the surface layer of the induction heat treatment to be hardened Screw bolt after the application of the known can be the surface carbon content of the kugeligei third heat treatment process., sorbitol, four-part of the ball head bolt easily by influencing a hundred times the magnification of the atmospheric gas dew point in the carburization

15, the fine structure of the inner part of the shaft 60 can be regulated in the process. If, therefore, the surfaces and the screw bolt part of the ball head bolt carbon content of the spherical part to about 0.60 ° / After the application of the heat according to the invention is selected, the surface layer of the kuge Treatment process, sorbitol + troostite + a gelige part due to the high frequency induction heat itffie amount of ferrite, magnification four hundred times, quenched treatment satisfactorily, and e 6 the fine structure of the shaft part of the spherical 65 is shown in the surface layer of the spherical egg h d Ad d Wäbhd part of a completely quenched martensitic

Structure. That is, the inner fine structure of the ball head bolt produced by the application of heat

or third heat treatment process and the surface layer and the inner part of the shaft or the screw bolt of the ball head bolt after applying the known second heat treatment process, Ferrite + troostite + a small amount of martensite, four hundred times magnification,

14 shows the photographically recorded common Fine structure of the surface layer of the shaft

j | g gg

Kbpfbolzens after the application of the heat treatment

day of the year according to the invention, ferrite + troostite

^ Wed four hundred times magnification, and

Io

obtained treatment method according to the invention is in clear contrast to that of the ball head bolt according to the known heat treatment process, in which a surface carbon content is achieved through the use of a carburizing gas atmosphere with a dew point of around -10 ° C is selected in a range of 0.7 to 0.9%, the diffusion heat treatment for improvement the machinability of the shaft part is carried out at a temperature of about 800 ° C, the is lower than the usually used carburizing temperature of about 900 ° C, and at which is then quenched and the internal fine structure obtained from a smaller amount Martensite and a large amount of troostite and ferrite.

According to the heat treatment method according to the invention, the blank is immediately after Carburizing and quenching process tempered in a temperature range between 420 and 430 ° C. The resulting fine structure is made of sorbitol, which is in the carburized surface layer is present, composed, while the fine structure of the inner part of sorbitol and a minor Amount of troostite and ferrite is composed. For this grand, the ball head bolt according to FIG Invention has excellent mechanical properties and improved toughness.

After the blank has been completely tempered, the entire surface of the spherical part continues to be subjected to high-frequency induction quenching or hardening. In this quenching or hardening treatment, the heating depth is in the range from about 0.6 to 0.8 mm. If necessary, a tempering treatment is carried out at a relatively lower temperature range, for example between 150 and 200 ^r C.

The ball head bolt produced by the described method according to the invention is in his Performance and its properties noticeably improved; besides, the manufacturing cost is compared to those of the ball head bolt produced by the known method is significantly lower.

F i g. 1 to 4 show temperature-time diagrams from which the results of the method according to the invention can be seen in comparison with those of the known methods; in this case, FIG. 1 details of the method according to the invention as a function of time, FIG. 2 the known first process, FIG. 3 the known second process and FIG. 4 the well-known third process. In the figures, the means .Y-axis is the heat treatment temperature and the F-axis is the heat treatment time. It means Farther

C ₁ : start of carburization (addition of the enrichment gas),

C ₂ : maximum heating temperature,
C _s : tempering temperature,

C ₃ ': diffusion temperature and quenching or hardening temperature,

C ₄ : tempering temperature at a relatively lower level,

OE on the F-axis: quenching or hardening time,

EH: payment period,
5

HJ: high frequency induction quenching time,

JM: compensation period at a relatively lower level,

Ca: carburization time,
d: diffusion treatment time.

With particular reference to FIG. 3 and 4, CC is the cooling time, OO 'is the carburization protection time, HM is the time required to remove the carburization protection, and JY is the cooling time in air.

ao As can be seen from Figs. 1 to 4, the heat treatment time OM for producing the ball head bolt according to the invention is compared with the treatment time in the known methods according to FIG. 2 to 4, the shortest. The remuneration

s5 temperature C ₃ is in the method according to the invention, as shown in FIG. 1 can be seen, around 420 ° C., whereas the tempering temperature C ₃ in the known first process is between 550 and 600 ° C., which is why the tempering time EH can be shortened in the process according to the invention. In addition, the payment time EH is both in the known second and in the known third method according to FIG. 3 and 4 respectively longer than in the method according to the invention, since the tempering treatment is carried out at a relatively lower temperature after the quenching.

The mechanical properties and other characteristics of the according to the method of the invention Ball head bolts produced are listed in Table 1, with the properties for comparison the known ball head bolts are indicated that are almost the same size as the inventive Have ball head bolts, have been produced by known methods and instantly used in Japan and the United States for automobiles and the like. A ball head bolt was used in this experiment in the form according to FIG. 5 a used. Its dimensions are as follows:

D - 26 mm 0,
d = 14.46 mm Φ, I = 22.4 mm,
L = 54 mm.

The ball center of the ball head bolt 1 is in the direction of arrow P according to FIG. 5 a loaded. To carry out the load tests 6, 7 and 8 ii Table 1, the ball head bolt 1 is attached to a clamping device 3 by means of a screw nut 2 P indicates the direction of the bending load, the falling load and the bending fatigue load. The Vei search results shown in Table 1 are based on experiments that took place over three years and in the years 1967 to 196 '

"*" ίο

were carried out. Those mentioned in Table 1 that both the deformation resistance and the

Structures and state variables are based on the deformation work performed in accordance with the invention

Heat treatment conditions of ball head pin-used carbon steel JIS · SCM-21 15 bis

zens and the fine values shown in FIGS. 8 to 17 are 20% lower than those of the steel JIS-SCM-4, the

structures. 5 for example in the known first manufacturing

The results of the load tests are from the procedure being applied. This is crucial-

5b and 5c can be seen. Fig. 5b shows the on the advantage with regard to the extension of the Le-

Bending stress exerted in the middle of the sphere. Service life of the tools used. So both

above the bend deflection, while F i g. 5 c, for example, a stamping tool made from quick

Absorption energy is produced over the bending deflection on the io lathe tool and for hollowing out a

Shows middle part of sphere. According to these results, the hollow ball head bolt is used in a

has the due to the heat deformation ratio according to the invention of 60 ° Ό about 10,000 to

Machining ball head bolts produced by the treatment process at JIS · SCM-21 steel, each

In comparison to the already known but only about 2000 to 5000 pieces at JIS ■ SCM-4-

Ball head made by heat treatment process - 15 steel. It is well known, by the way, that a

Bolts have excellent shock resistance - less difference in resistance to deformation

ability, strength and elasticity. Before all or flow resistance of the steel to be machined

Things are shown by the ball head bolt according to the invention or the alloy to be processed, in particular

as shown in FIG. 5 b can be seen in the bending test when working with a high deformation ratio

no break. * ° nis, a considerable effect on the service life

F i g. 6 shows the hardness distribution of the ball of the finished tool and the efficiency of the manufacturing

term ball head bolt, whereby the hardness change exerts the treatment process as mentioned above.

Spherical surface over the distance from the upper The most essential features of the invention are

surface of the spherical part are applied. In summary, the following:

Curve A shows the hardness distribution of the spherical 95. Above all, according to the invention, as part of which a low-carbon steel or induction heating process is quenched by the high-frequency starting material according to the invention or a low-carbon alloy steel that has been hardened is used, while curves B , C and D is excellent workable at room temperature. so in each case according to the hardness distributions of the first, second and third processes, which are known more easily at room temperature, and can be carried out more effectively. Corresponding ball-headed bolts. From this, a relatively low carburizing carbon hardness distribution curve is clear that the material content of the surface carburizing layer, for example about 0.6 ¹ Vo, with a relatively low frequency induction hardening in the surface layer carburizing thickness of the surface of about 0, is due to the additional high according to the invention , 3 to the spherical part provided a superior hardness distribution 35 0.5 mm; the chosen diffusion treatment gives, although the carburization concentration and temperature is just as high as the carburization depth is less. The curve A ' shows the quenching or hardening temperature. so that the hardness distribution of the invention, due to the improved, excellent hardening ball-headed bolt, is heated up for a low-carbon steel before the high-frequency induction effect. 40 gives a sufficiently good hardness structure; the remuneration

In Fig. 6, the ordinate indicates the hardness value according to the treatment treatment used for a common one the Rockwell C scale and the abscissa the respective carbon steel applied tempering tempera depth of the surface layer in mm. The acceptance door carried out so that the mechanical own between the hardened surface layer and the shafts, for example toughness or ductility inner part is small, from which the notable 45 fatigue limit, tensile strength or breaking strength impact advantages the carburization and high frequency heat load resistance, load capacity and the like, remark treatment according to the invention can be significantly improved. Finally will will. the high frequency induction hardening process only

Since in the method according to the invention, as in the case of the spherical part of the ball head bolt,

described above, a carbon 50 turns as the starting material, producing a ball head bolt

low-carbon steel or a low-carbon alloy, which despite its low carburization depth and

steel, which has a C content of 0.12 to 0.23% C of its low carbon content

and has excellent properties with regard to wear resistance at room temperature

Workable is used, can have the service life and ductility. In addition,

of the punch, which is made of high-speed steel, 55 which is produced by the method according to the invention

and for hollowing out the hollow ball head bolt adjustment of the ball head bolt

will be remarkably lengthened. the necessary time and the

From Fig. 7 is the deformation ratio counter manufacturing costs considerably reduced The erfinüber the deformation resistance or geleiste- dung proper heat treatment process also th deformation work can be seen, where K ,, K ₁ '60 verdem for producing an article or a part deformation resistance (kg / mm ²⁾ Steels are used in which for a limited part correspond to JIS · SCM-21 or JIS · SCM-4, while this article has a characteristic wear resistance ω, ω ' of the deformation work performed (nim- kg / keit and at the same time for the remaining part this mm ^s ) the steels JIS · SCM-21 or JIS-SCM-4 correspond to a special toughness and strength that speak. Accordingly, 63 is required for the ordinate, as is the case, for example, with valve values kg / mm ² and mm-kg / mm ^s , while the tappets, valve adjusting screws and the like are the case indicates steels in Vo for use in internal combustion engines. From Fig. 7 it is easy to get.

Table 1

12th

Characteristic properties of the ball head bolts produced according to the invention compared to those according to

the known method produced

Characteristic properties

Heat treatment

proceed according to

the invention

1. Procedure
(exercised in Japan)

Treatment method
State of the art

2. Procedure
(exercised in Japan)

3. Procedure (carried out in the USA)

Material quality (main components) (%)

Treatment process after cold working

Tensile strength of the screw bolt part (σ _β : kg / mm ² )

Yield strength of the screw bolt (o _s : kg / mm ² )

Tensile strength of the shaft part (σ _β : kg / mm ² )

Yield point (a _s : kg / mm ² ) elongation (σ: ° / o)

Surface carbon concentration ( ⁰ / o)

Metal structure
and
other
conditions

Carburization depth (mm)

Hardness (HRc)

Bullet

Shaft and
Bolt

surface

Inner part

surface

Inner part

JIS · SCM-21 C: 0.15
Cr: 0.9
Mo: 0.20

Carburization hardening (900 ° C)

■ Quenching and tempering (420 ° Q- * high frequency induc hardening -V quenching and tempering at low temperature (200 ° C)

120 ~ 130
110 ~ 120
110 120

80 90

18 19

0.5 to 0.7

0.3 to 0.6

62 to 63
Martensite (Fig. 8)

Sorbitol + troostite + ferrite (Fig. 9)

Sorbitol (Fig. 14)

JIS · SCM-21
C: 0.4
Cr: 0.9
Mo: 0.2

Editing the
Spherical surface

■ hardening
(850 ° C) - »- quenching and tempering (580 ⁰ C)

- High frequency induction hardening

■ Remuneration at
low temperature (200 ° C)

110 ~ 120

90 ~ U0

120

110
19th

up to 60
Martensite (Fig. 8)

Sorbitol (Fig. 11)

Sorbitol (Fig. U)

Sorbit-I-Troostit + a smaller one Amount of ferrite (Fig. 15)

Sorbitol (Fig. 11)

JIS-SCM-21
C: 0.16
Cr: 0.9
Mo: 0.2

Carburization protection -> - Carburization (900 ° C)

- Diffusion hardening (350 ⁰ C)

- Compensation at
low temperature (200 ⁰ C)

Removal of the
Carburization protection

90 ~ 100

65 ~ 75
95

65
19th
0.7 to 0.9

0.5 to 0.8

up to 64

Martensite + rest
Austenite (Fig. 12)

Ferrite + stroostite
+ a smaller one
Amount of martensite
(Fig. 13)

Ferrite + troostite
+ a smaller one
Amount of martensite
(Fig. 13)

Ferrite + troostite
+ a smaller one
Amount of martensite
(Fig. 13)

according to JIS-SCM-21 C: 0.2
Cr: 0.5
Ni: 0.5
Mo: 0.2

Carburization (900 ° C) -v diffusion hardening (850 ° C) -v quenching and tempering at low temperature (200 ° C) - ^ high frequency induc tempering of the thread - * · air cooling

90 ~ 100

60 ~ 75
90 95

60 65
18 19
0.7 to 0.9

0.5 to 0.8

62 to 64

Martensite + remainder austenite (Fig. 12

Ferrite + Troostite + a smaller amount of Martensil (Fig. 13)

Thread part: sorbitol (Fig. 14), shaft part: ferrite + troostite
+ Martensite (Fig. 16)

Ferrite + Troostite + a smaller amount of Martensi (Fig. 17)

13th Height of fall (mm)
one on the
spherical part
impinging
30 kg weight
before generation
a break Bath treatment
proceed according to
the invention ]
1. Procedure
(exercised in Japan) 14th 1
3. Procedure
(exercised in USA) Characteristic Christian traits Height of fall (mm)
one on the
spherical part
impinging
30 kg weight
before generation
of a strong one
Break 35 to 40 28 to 34 Proceedings of action
State of the art
2. Procedure
(exercised in Japan) 28 to 32 Hardness of the inner part (HRc) 2,700 kg 2,000 kg 28 to 32 1,800 kg 6th Flexural strength of the conical
Part of the shaft, loaded on
of the sphere (fracture generation:
Fig. 5b) 700,000 cycles 100,000 cycles 1,800 kg 69,000 cycles 7th Fatigue strength (bending)
(P _max of fracture generation:
1000 kg cycle, P _min : 100 kg) 1,200 1,000 60,000 cycles 260 8th Firm
speed
against
above
Push and
Blow 71,500 1,500 360 1,000 1,200

The steels listed above in detail in the form of abbreviations have the following combinations Settlements on:

Composition (° / o)

C. Si Mn Ni Cr Mo y P 0.030 S. S-15C Max (J1SS-15C) .... 0.10-0.20 - 0.30-0.60 - - - S-20C 0.15-0.25 0.30-0.60 SCM-21 (JIS-SCM-21) .. 0.13-0.18 0.15-0.35 0.60-0.85 - 0.90-1.20 0.15-0.35 SCM-22 0.18-0.23 0.15-0.35 0.60-0 85 0.90-1.20 0.15-0.35 SCM-23 0.17-0.23 0.15-0.35 0.60-0.85 0.90-1.20 0.15-0.35 SCM-4 (JIS-SCM-4) ... 0.38-0.43 0.15-0.35 0.60-0.85 - 0.90-1.20 0.15-0.35 0.030 SNCM-21 0.17-0.23 0.15-0.35 0.60-0.90 0.40-0.70 0.40-0.65 0.15-0.35 Max SNCM-22 0.12-0.18 0.15-0.35 0.40-0.70 1.60-2.00 0.40-0.65 0.15-0.35 SNCM-23 0.17-0.23 0.15-0.35 0.40-0.70 1.60-2.00 0.40-0.65 0.15-0.35 SNCM-24 0.17-0.23 0.15-0.35 0.70-1.10 2.80-3.40 1.50-2.00 0.30-0.50 SNCM-25 U, 12-0.18 0.15-0.35 0.30-0.60 4.00-4.50 0.70-1.00 0.15-0.30 SNCM-26 0.13-0.20 0.15-0.35 0.80-1.20 2.80-3.20 1.40-1.80 0.40-0.70

In addition 8 sheets of drawings

Claims (3)

This ball head bolt made of low-alloy carbon steel is generally denied claims: quenched or hardened and then tempered. 1. Process for the production of a spherical head temperature by high-frequency electric induction handbolting Made of carbon steel or alloy steel, case-hardened and tempered. by successive carburization quenching or case hardening, diffusion treatment, tempering or tempering treatment ic and high frequency induction hardening treatment, 2. Second method which only apply to the spherical part of the
Ball head bolt is limited, thereby indicates that a case-hardened or case-hardened steel is used as the starting material Carbon steel with 0.13 to 0.18% C, 0.9 to 15 a carbon content of 0.15 to 0.23% will be 1.2% Cr, less than 0.30% Ni, 0.15 to 0, 30% starting material is used and all parts except Mo, 0.15 to 0.35% Si, 0.60 to 0.85% Mn, and the spherical part of the ball head bolt is used with the remainder being iron, that the carbide is a Copper plating or other suitable temperature hardening treatment means given a carburization preventive treatment; from 890 to 920 ° C is carried out so that the case hardening and the long-term diffusion treatment are then carried out at one of the temperature tempering treatment at a low temperature of the carburization hardening treatment about temperature. Finally, the layers formed by the speaking temperature are carried out that the anti-carburization treatment removes the tempering or tempering treatment at one.
Temperature above 430 ° C is carried out and 25
that the high frequency induction hardening treatment ment exclusively on the spherical part of the third third procedure Ball head bolt is limited. 2. The method according to claim 1, characterized in that in the carburized upper 30 A case-hardening steel with a carbon content of surface layer of the ball head bolt a carbon 0.15 to 0.23% is used as the starting material for the material content set between 0.5 and 0.7% ball head bolts used. Whose entire upper part, at a low temperature, the surface becomes 3. The method according to claim 1 or 2, characterized in set hardening treatment and a long-term Vergado, that the depth of carburization of the 35 processing treatment subjected, after which the with a Ball head bolt set to 0.3 to 0.6 mm threaded part of the ball head bolt through will. the high frequency induction heat treatment driving is remunerated and then slowly cooled down. The three known methods described above 40 have different advantages as well as different, disadvantages described below, i. i.e., according to The inherited process is a low-alloy steel with more than 0.40% C used to make a pretty maintain great hardness, even after the 45 by means of high frequency induction heating or -heating carried out heat treatment of the The invention relates to a method for producing spherical parts. This has a noticeable resistance a ball head bolt, which is responsible for steering or increasing deformation in the case of the kom-suspension device a motor vehicle used cold forming process result and is bar; In particular, it relates to a heat treatment that shortens the life of the deformation process, where a low-carbon steel testifies. If in addition to the original material or a low-alloy steel as a starting material a decarburization layer, i.e. a layer with For the production of a hollow ball-headed bolt use less C, is available, it turns out after the upheaval which is not the desired when stressed by induction hardening Crash-like and variously large impact loads- 55 surface hardness in the starting material, because these genes, vibrations and various other decarburization layers less or no C defaced Strains a long service life. This has the consequence that the wear resistance <knows. The method of heat treatment and the stand of the spherical part of the ball head bolt in is usually considerably reduced for the manufacture of the ball head bolt in general. It is to be used Materials are required as follows, the entire surface layer divided or differentiated: the ball head bolt or the ball surface to remove to remedy the above mentioned problem.