CN101835916A

CN101835916A - Steel for CVJ ball cages

Info

Publication number: CN101835916A
Application number: CN200880112822A
Authority: CN
Inventors: 近藤邦夫; 山本忠之
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Nippon Steel Corp
Priority date: 2007-10-22
Filing date: 2008-10-22
Publication date: 2010-09-15
Anticipated expiration: 2028-10-22
Also published as: JP5071038B2; CN101835916B; JP2009102684A; MX2010004254A; WO2009054394A1; KR20100059951A

Abstract

A steel for CVJ ball cages which contains by mass C: 0.1 to 0.25%, Si: 0.05 to 0.7%, Mn: 0.05 to 1.2%, Cr: 0.3 to 1.2%, S: 0.005% or below, P: 0.03% or below, N: 0.02% or below, O (oxygen): 0.01% or below, and sol. Al: 0.005 to 0.1% with the balance consisting of Fe and unavoidable impurities, which may further contain one or more elements selected from among Mo, Ni, Ti, V and Zr instead of part of Fe, and which can attain a sufficient lifetime even when used for a ball cage of a downsized and lightened CVJ to be subjected to a stress greater than conventional.

Description

CVJ ball cage steel

Technical field

The present invention relates to ball cage (ball cage) steel that part adopted of the constant velocity cardan joint (CVJ) of a kind of automobile etc.

Background technology

As shown in Figure 1, automobile to be used for from drive axle be such structure to the constant velocity joint that is driven the axletree transferring power (hereinafter to be referred as making CVJ), promptly, insert a plurality of balls 5 between outer ring (outer race) (outer shroud) 4 on the driven shaft 2 being fixedly set in the interior figure (inner race) (interior ring) 3 on the drive shaft 1 and being fixedly set in, utilize ball cage 6 to keep these balls.Because this ball cage 6 and inner ring 3 will transmit very large revolving force in mechanism, therefore, need higher intensity, toughness and fatigue strength.

Thereby, use the converted steel (case-harde ned steel) of having been paid higher surface hardness by carburizing, quenching and having rotated fatigability for these parts, as converted steel, the physical construction steel alloy that such Cr system, Cr-Mo system, Ni-Cr system, the Ni-Cr-Mo of SCr415, SCM415, SNC415, SNCM415 that in the past adopted JIS is.

But recently, for the requirement increase of CVJ miniaturization and, the stress that acts on ball cage compared with the past becomes big.In converted steel in the past,, therefore, for example as following patent documentation 1～5, proposed to solve the technology of the problems referred to above point by the research alloy composition because static strength, toughness and fatigue strength are not enough.

In patent documentation 1, disclose and make Cr-Mo amount suitableization and add Nb or steel that Ti forms, in patent documentation 2, disclose the steel that Cr-Mo suitableization of amount and interpolation Nb or Ti and interpolation B, Ni are formed.In patent documentation 3 and 4, disclose and make Cr-Mo suitableization of amount and add the steel that B forms.In addition, in patent documentation 5, disclose the steel that interpolation B forms in the Cr steel.

Patent documentation 1: Japanese kokai publication hei 1-39351 communique

Patent documentation 2: Japanese kokai publication hei 5-117806 communique

Patent documentation 3: Japanese kokai publication hei 9-53150 communique

Patent documentation 4: Japanese kokai publication hei 9-53169 communique

Patent documentation 5: TOHKEMY 2005-105379 communique

But the converted steel that proposes in these patent documentations is compared with the steel of JIS defined and is all had the problem that cost of alloy is higher, manufacturing also reduces.Also exist the life-span compared with the past to reduce such problem.

Summary of the invention

The object of the present invention is to provide a kind of CVJ ball cage steel, though this CVJ ball cage with steel than be applied to act on than the ball cage of bigger in the past bearing strength test among the CVJ of miniaturization and more, also can obtain enough durable life-spans in the past.

The inventor investigates in minute detail than among the CVJ of miniaturization and, that effect has the ball cage than bigger in the past bearing strength test just can't use at short notice more example in the past, and analyze the reason that influences the life-span most, studied its method of life of prolongation.As a result, obtain the opinion shown in following (a)～(h).

When (a) increasing the joint corner cut of CVJ in the high speed rotating process, the stress that ball cage is loaded surpasses the strength of materials, causes the ball cage fracture.Thereby it is very important improving the strength of materials.

(b) adopt the higher material of intensity to make the ball cage of CVJ and implemented long duration test, even but high-strength material, when in the high speed rotating process, increasing the joint corner cut of CVJ with the CVJ of reality, whether the destruction that yet can't suppress ball cage, causing ball cage to destroy does not have corresponding relation with the simple strength of materials.

(c) whether can suppress ball cage destruction and investigate improving surface hardness or raising toughness, but all can't improve strength at break, the situation of Jiang Diing is also a lot of on the contrary.

(d) investigation result according to joint corner cut that increases CVJ with the CVJ of reality in the high speed rotating process and ball cage destructive corresponding relation can be clear and definite, and ball cage ruptures and is to begin to take place from the stress concentration portion of the corner part of the window that is used for fixing ball.Therefore, demonstrate good corresponding relation with the intensity of notch tension test as can be known.

The material design objective of the breaking tenacity when (e) thereby as can be known, being used to improve with converted steel as the member of the such characteristic shape of ball cage is to improve notch tensile intensity (Notched tensile strength).That is, under the situation that makes the ball cage miniaturization and, it is big that the stress of being loaded becomes, but in this case, when desiring to guarantee with the breaking tenacity more than the equal extent in the past, as long as improve notch tensile intensity.

(f) then, the notch tensile intensity that improves the converted steel that is used as ball cage has been implemented research.The result can be clear and definite, and as aftermentioned, notch tensile intensity depends on the S amount largely.Relative therewith, common tensile strength does not also rely on the S amount.Converted steel also can be used for various uses such as gear, carries out machining mostly.But, consider from the aspect of guaranteeing machinability, add S usually energetically, but change thinking specifically and reduce S amount in the steel, found that notch tensile intensity obviously raises.That is, in order to improve notch tensile intensity, enable promptly to estimate that machinability can reduce, reducing the S amount also is unique method.

(g) observe according to the section after the tension test, the raising that reduces the notch tensile intensity behind the S depends on that what of inclusion the MnS that has extended be.In notch tension test, stress concentration is in notch part at the trial, if under stress concentration portion, have the MnS that has extended, then can become the destructive starting point, carburizing portion produces brittle rupture, and, because the toughness of the central part of carburizing does not reduce because of the MnS that has extended yet, therefore, in case crack in early days, then crack growth does not stop and can rupturing under low-stress.In common tension test, even there is the MnS extended, there is not the breach of stress concentration yet, therefore, carburizing portion is difficult to produce brittle rupture, and rupture stress raises.Thereby when reducing MnS reducing the S amount and being the inclusion amount, common tensile strength can rise hardly, but can improve notch tensile intensity widely.Purposes of the present invention, be the domination that strength at break during ball cage uses is subjected to this notch tensile intensity, therefore, by reducing the S amount, even can provide miniaturization also to be difficult to destructive, the higher CVJ of reliability.In addition, this effect is fit to the technology of the so peculiar Shape Parts of ball cage, for other purposes that are subjected to common tensile strength, fatigue strength domination, almost can't expect the effect that this S amount reduces, can reduce machinability on the contrary, therefore, be not the technology that can use.

(h) Fig. 2～17th is X-axis, is that the drafting of Y-axis ground forms with the mechanical properties with the S amount for the steel with various chemical constitutions that adopts in embodiment described later.In addition, as mechanical properties, common tensile strength (level and smooth tensile strength) and notch tensile intensity are used as its index.

Fig. 2 and Fig. 3 are arrangements with SCr415 is basis and change the graphic representation that level and smooth tensile strength after the carburizing of steel (steel No.1～8) of S amount and notch tensile intensity form.As shown in Figure 2, even reduce the S amount, level and smooth tensile strength is also almost constant.But as shown in Figure 3, notch tensile intensity changes greatly because of the S amount, and when the S amount in the reduction steel, its intensity rises significantly.

Then, Fig. 4 and Fig. 5 are that having put in order with SCM415 is basis and change level and smooth tensile strength steel (steel No.9～16), after the carburizing of S amount and the graphic representation of notch tensile intensity; Fig. 6 and Fig. 7 are that having put in order with SCr420 is basis and change level and smooth tensile strength steel (steel No.17～24), after the carburizing of S amount and the graphic representation of notch tensile intensity; Fig. 8 and Fig. 9 are that having put in order with SCr420 is basis and change level and smooth tensile strength steel (steel No.25～32), after the carburizing of S amount and the graphic representation of notch tensile intensity; Figure 10 and Figure 11 are that having put in order with SAE8617 is basis and change level and smooth tensile strength steel (steel No.33～41), after the carburizing of S amount and the graphic representation of notch tensile intensity; Figure 12 and Figure 13 have put level and smooth tensile strength steel (steel No.42～49), after the carburizing of the change S amount to add steel that Ti forms in SCr415 system and the graphic representation of notch tensile intensity in order; Figure 14 and Figure 15 have put level and smooth tensile strength steel (steel No.50～57), after the carburizing of the change S amount to add steel that Nb forms in SCM420 system and the graphic representation of notch tensile intensity in order; Figure 16 and Figure 17 have put level and smooth tensile strength steel (steel No.58～65), after the carburizing of the change S amount to add steel that Ti, Nb form in SAE8617 system and the graphic representation of notch tensile intensity in order.Same with Fig. 2 and Fig. 3, even reduce the S amount, level and smooth tensile strength is also almost constant, but when the S amount in the reduction steel, notch tensile intensity rises significantly.

The present invention promptly finishes according to above-mentioned opinion, and its purport is the CVJ ball cage steel of following (1)～(4).

(1) a kind of CVJ ball cage steel, it is characterized in that, in quality % contain C:0.1～0.25%, Si:0.05～0.7%, Mn:0.05～1.2%, Cr:0.3～1.2%, below the S:0.005%, below the P:0.03%, below the N:0.02%, O (oxygen): below 0.01% and sol.Al:0.005～0.1%, rest part is made of Fe and impurity.

(2) the CVJ ball cage steel of above-mentioned (1) is characterized in that, in quality %, substitutes the part of Fe and also contains below the Mo:0.7%.

(3) the CVJ ball cage steel of above-mentioned (1) or (2) is characterized in that, in quality %, substitutes the part of Fe and also contains below the Ni:1%.

(4) each CVJ ball cage steel in above-mentioned (1)～(3), it is characterized in that, in quality %, substitute the part of Fe and also contain Ti:0.3% below, Nb:0.3% is following, V:0.3% is following and below the Zr:0.3% in more than one.

Adopt the present invention, a kind of CVJ ball cage steel be provided, though this CVJ ball cage with steel more in the past than the ball cage that was applied to act among the CVJ of miniaturization and more than bigger in the past bearing strength test, also can obtain enough durable life-spans.

Description of drawings

Fig. 1 is the sectional view of an example of expression constant velocity joint.

Fig. 2 represents that SCr415 is the relation of S amount and level and smooth tensile strength in the steel grade.

Fig. 3 represents that SCr415 is the S amount in the steel grade and the relation of notch tensile intensity.

Fig. 4 represents that SCM415 is the relation of S amount and level and smooth tensile strength in the steel grade.

Fig. 5 represents that SCM415 is the S amount in the steel grade and the relation of notch tensile intensity.

Fig. 6 represents that SCr420 is the relation of S amount and level and smooth tensile strength in the steel grade.

Fig. 7 represents that SCr420 is the S amount in the steel grade and the relation of notch tensile intensity.

Fig. 8 represents that SCM420 is the relation of S amount and level and smooth tensile strength in the steel grade.

Fig. 9 represents that SCM420 is the S amount in the steel grade and the relation of notch tensile intensity.

Figure 10 represents that SAE8617 is the relation of S amount and level and smooth tensile strength in the steel grade.

Figure 11 represents that SAE8617 is the S amount in the steel grade and the relation of notch tensile intensity.

Figure 12 represents to add the relation of S amount and level and smooth tensile strength in the steel grade that Ti forms in SCr415 system.

Figure 13 represents to add the S amount in the steel grade that Ti forms and the relation of notch tensile intensity in SCr415 system.

Figure 14 represents to add the relation of S amount and level and smooth tensile strength in the steel grade that Nb forms in SCM420 system.

Figure 15 represents to add the S amount in the steel grade that Nb forms and the relation of notch tensile intensity in SCM420 system.

Figure 16 represents to add the relation of S amount and level and smooth tensile strength in the steel grade that Ti and Nb form in SAE8617 system.

Figure 17 represents to add the S amount in the steel grade that Ti and Nb form and the relation of notch tensile intensity in SAE8617 system.

Description of reference numerals

1, drive shaft; 2, driven shaft; 3, inner ring; 4, outer ring; 5, ball; 6, ball cage.

Embodiment

Below, describe with the qualification reason of the chemical constitution of steel constituting CVJ ball cage of the present invention.In addition, " % " expression " quality % " of the amount of each element.

C：0.1～0.25％

Because C is the hardness of decision steel or the fundamental element of intensity, therefore, is the element that adds according to desired intensity.In order to ensure the minimum intensity as ball cage, the amount that need make C is more than 0.10%.On the other hand, if the amount of C is too high, then toughness reduces, therefore, make the C amount on be limited to 0.25%.

Si：0.05～0.7％

Si has the effect that makes steel-deoxidizing, and, be to improve hardening capacity and the element of strengthening steel, the amount that need make Si is more than 0.05%.But, if the amount of Si greater than 0.7%, then encourages grain boundary oxidation when carburizing and quenching, notch tensile intensity is reduced, therefore, make the Si amount on be limited to 0.7%.In addition, consider that preferred Si amount is lower from the aspect of notch tensile intensity.Consider also and the balance of deoxidation degree (deacidification level) that the amount of preferred Si is below 0.5%, more preferably below 0.3%.

Mn：0.05～1.2％

Mn also similarly has the effect that makes steel-deoxidizing with Si, and, be to improve hardening capacity and the element of strengthening steel, the amount that need make Mn is more than 0.05%.But, if the amount of Mn greater than 1.2%, then encourages grain boundary oxidation when carburizing and quenching, notch tensile intensity is reduced, therefore, the amount that makes Mn is below 1.2%.In addition, consider that preferred Mn amount is lower from the aspect of notch tensile intensity.Consider also and the balance of deoxidation degree that the amount of preferred Mn is below 1.0%.

Cr：0.3～1.2％

The affinity of Cr and C is bigger, is to carry out the necessary element of carburizing at short notice.In addition, also be the important element of the hardening capacity when guaranteeing carburizing and quenching.In order to obtain this effect, the amount that need make Cr is more than 0.3%.On the other hand, if the amount of Cr is greater than 1.2%, then the Cr carbide is separated out and toughness is reduced.Thereby making the Cr amount is 0.3～1.2%.

Below the S:0.005%

Suppressing the S amount lower is the most important characteristic of steel of the present invention, greater than 0.005%, then can't guarantee the notch tensile intensity that needs as if the S amount.Thereby the amount that makes S is below 0.005%, and more preferably below 0.003%, more preferably below 0.0015%, the S amount is low more, and notch tensile intensity is high more.But, along with the reduction of S exists machinability to reduce such problem, and, then can cause making the steel cost and rise if reduce S, therefore, under the situation of considering these problems, the lower limit of preferred S amount is greater than 0.0009%.

Below the P:0.03%

P is included in the steel as impurity.P reduces the bonding force of crystal boundary and element that toughness is reduced, and is preferably few as much as possible, but low-level if desire is suppressed at the amount of P, then making the steel cost can rise, and therefore, considers economy, and the amount that makes P is below 0.03%.If making the amount of P is below 0.03%, then can obtain sufficient toughness as ball cage.

Below the N:0.02%

N is included in the steel as impurity.If the amount of N is greater than 0.02%, then toughness reduces, and therefore, the amount that makes N is below 0.02%.More preferably the amount of N on be limited to 0.01%, be limited to 0.007% on further preferred.

O (oxygen): below 0.01%

O is included in the steel as impurity.If the amount of O is greater than 0.01%, then toughness reduces, and therefore, the amount that makes O is below 0.01%.

sol.Al：0.005～0.1％

Al is the necessary element of steel-deoxidizing, need contain more than 0.005%.On the other hand, if the amount of Al greater than 0.1%, then can generate the non-metallic inclusion of pencil and toughness is reduced, therefore, the amount that makes sol.Al is 0.005～0.1%.

CVJ ball cage of the present invention also can also contain among Mo, Ni, Ti, Nb, V and the Zr more than one with high strength converted steel except that mentioned component.In this case, need similarly to suppress P, N and O lower as described above.

Below the Mo:0.7%

Mo has the hardening capacity that improves carburizing portion, the effect that improves hardness of steel.Thereby, embody in desire under the situation of this effect, can contain Mo.But the amount of Mo is that 0.7% o'clock effect will be saturated, even the amount of Mo greater than 0.7%, also only causes cost to rise.Thereby, even containing under the situation of Mo, also make its amount on be limited to 0.7%.In addition, in order to obtain this effect, the amount that preferably makes Mo is more than 0.1%.

Below the Ni:1%

Ni has intensity and the flexible effect that improves steel.Different with Cr, Mo, even it is to add the also less element of detrimentally affect in large quantities, therefore, be effective especially composition for the higher material of design strength.Thereby, embody in desire under the situation of this effect, can contain Ni.But the amount of Ni is that 1% o'clock effect will be saturated, even the amount of Ni greater than 1%, also only causes cost to rise.Thereby, even containing under the situation of Ni, also make its amount on be limited to 1%.In addition, in order to obtain this effect, the amount that preferably makes Ni is more than 0.1%.

Ti, Nb, V and Zr: separately below 0.3%

These elements have coarse-grainization, the effect of raising flexible of crystal grain when suppressing carburizing and quenching.Thereby, embody in desire under the situation of above-mentioned effect, can contain among Ti, Nb, V and the Zr more than one.But if separately amount is greater than 0.3%, then toughness reduces on the contrary, therefore, even under the situation of more than one in containing Ti, Nb, V and Zr, also make separately amount on be limited to below 0.3%.In addition, in order to obtain this effect reliably, the amount that preferably makes Ti, Nb, V and Zr is more than 0.003%.

In addition, CVJ ball cage of the present invention with steel after being processed as the shape of ball cage, through carburizing and quenching and temper and as the part of CVJ.

Embodiment

The steel of the chemical constitution shown in melting table 1 and the table 2 carry out heat forged and hot rolling system and make the sheet material that 25mm is thick, 120mm is wide, 550mm is long it, after carrying out normalizing with 920 ℃, implement tempering and make it softening with 720 ℃.Then, remove surface scale, it is thick afterwards it to be cold working to 16mm, makes it softening with 720 ℃ of enforcement tempering once more.

Table 1

Table 2

From above-mentioned raw materials upper edge and the vertical direction of rolling direction be the T direction take respectively the diameter of parallel portion be the level and smooth tension test sheet of 8mm and similarly the diameter of parallel portion be the notch tension test sheet of 8mm and breach with degree of depth 1mm.Then, under following condition, test film is implemented carburizing treatment and thermal treatment.

At first, with carbon potential 0.9%, 930 ℃ of carburizings 130 minutes, then,, carry out oil quenching afterwards with carbon potential 0.8%, 870 ℃ of carburizings 30 minutes.Then,, measure level and smooth tensile strength and notch tensile intensity, estimate its mechanical properties with 160 ℃ of tempering 2 hours.The measurement result of level and smooth tensile strength and notch tensile intensity is shown in table 1 and the table 2.

Fig. 2～17th, aforesaid, as to adopt this table 2 data pin is X-axis, be the graphic representation that the Y-axis drafting forms with mechanical properties (level and smooth tensile strength, notch tensile intensity) with the amount of S every kind of steel grade.Even reduce the S amount, level and smooth tensile strength is also almost constant, but the S amount of notch tensile intensity in steel can rise when reducing significantly.

Industrial applicibility

When CVJ ball cage of the present invention is applied to act on the ball cage of bigger bearing strength test in the CVJ of miniaturization and with steel, can obtain enough Durabilities. Thereby, go far towards to improve lightweight and the fuel consumption charge of automobile.

Claims

1. a CVJ ball cage steel is characterized in that,

In quality %, contain that C:0.1～0.25%, Si:0.05～0.7%, Mn:0.05～1.2%, Cr:0.3～1.2%, S:0.005% are following, P:0.03% is following, N:0.02% is following, O (oxygen): reach sol.Al:0.005～0.1% 0.01% below, rest part is made of Fe and impurity.

2. CVJ ball cage steel according to claim 1 is characterized in that,

In quality %, substitute the part of Fe and also contain below the Mo:0.7%.

3. CVJ ball cage steel according to claim 1 and 2 is characterized in that,

In quality %, substitute the part of Fe and also contain below the Ni:1%.

4. according to each described CVJ ball cage steel in the claim 1～3, it is characterized in that,

In quality %, substitute the part of Fe and also contain Ti:0.3% below, Nb:0.3% is following, V:0.3% is following and below the Zr:0.3% in more than one.