DE102019117288A1 - Machine element and use of a machine element - Google Patents

Abstract

The invention relates to a machine element (1) made of steel, which is hardened on its surface (13) by nitriding at least in some areas and has a surface hardness of ≥ 650 HV 1 and a nitriding depth (NHD) of ≥ 0.1 mm, the machine element ( 1) is lubricated in the area of nitriding by means of a water-based lubricant (2) or a water-based cooling lubricant (2 '), each having a water content of ≥ 20% by weight. The invention further relates to the use of a machine element (1).

Description

The invention relates to a machine element made of steel and the use of a machine element made of steel. To minimize friction, machine elements are often used together with lubricants or cooling lubricants on site.

A number of steels are available for the manufacture of machine elements. For example, through-hardened (martensitic or bainitic) or surface-hardened (case-hardened, carbonitrided or inductively hardened) materials are used for rolling bearings as well as surface-hardened materials (case-hardened, carbonitrided or inductively hardened) for gearwheels. With appropriate surface treatments, these materials are very well suited for use in lubricants containing hydrocarbons.

However, water-based lubricants or water-based cooling lubricants with a water content of ≥ 20% by weight are now becoming increasingly important in the automotive drive train. An expansion of their use to industrial applications is also foreseeable. The main reason for this is that friction losses in a drive train should be reduced as much as possible. At the same time, after water forms a large part of it, such a lubricant offers good properties with regard to heat transfer and heat dissipation.

The DE 10 1009 039 626 A1 discloses a water-based lubricant for the lubrication of chains, gears, roller and plain bearings and seals on rotating shafts.

However, the use of water-based lubricants or cooling lubricants poses new challenges for machine elements made of steel, especially if they are in rolling contact. It was found that machine elements made of standard materials fail in such applications before the calculated or designed service life. This is attributed in particular to embrittlement of the steel with hydrogen, which comes from the water-based lubricant or cooling lubricant. The machine elements fail prematurely, so that the calculated service life values (see ISO / TS 16281 from June 15, 2008 for rolling bearings; see ISO6336ff. From September 1, 2006 for gears) are not achieved.

In the case of roller bearings in particular, but also in the case of gearwheels in gearboxes, significantly reduced service lives have been found when lubricated with water-based lubricants or cooling lubricants. Any corrosion problems on the machine elements could be solved by using suitable additives in the water-based lubricants.

In particular for water-based cooling lubricants in the form of flame-retardant hydraulic fluids, the application of coatings, such as thin-layer chrome plating, or the use of alternative steels such as AISI440C or material no. 1.4108 (X30CrMoN151), recognized.

So it has already been possible to use suitable special materials, such as the above-mentioned steel with material no. 1.4108, achievable service life of machine elements even in water-based lubricants. The widespread use of such special materials is countered by their high material and manufacturing costs.

It is therefore an object of the present invention to provide an inexpensive machine element made of steel which can be used in water-based lubricants or cooling lubricants with a long service life.

The object is achieved for a machine element made of steel by hardening its surface at least in regions by means of nitriding and having a surface hardness of ≥ 650 HV 1 and a nitriding hardness depth (NHD) of ≥ 0.1 mm. The machine element is lubricated in the area of nitriding using a water-based lubricant or a water-based cooling lubricant, each having a water content of ≥ 20% by weight.

Nitrable steels are inexpensive and, after nitriding, are surprisingly more robust than early failures in water-based lubricants or cooling lubricants.

Both the complete surface of the machine element and only a partial area of the surface of the machine element can be hardened by nitriding. The only decisive factor here is that the water-based lubricant or cooling lubricant does not come into contact with a non-nitrided and thus unhardened steel surface in a surface area subjected to rolling.

The machine element is therefore preferably made of nitriding steel. Nitriding steels contain, among other things, nitride formers as alloy components. The elements from the group comprising aluminum, boron, chromium, niobium, titanium, Vanadium, zircon. A steel made of 31CrMoV9 or 32CrMoV13 has proven particularly useful.

In the area of nitriding, the machine element is particularly preferably lubricated by means of a water-based lubricant or a water-based cooling lubricant, each having a water content in the range from 20 20% by weight to <50% by weight.

A mixture of water, glycols and additives (organic and / or inorganic salts), in particular with such a water content in the range from ≥ 20% by weight to <50% by weight, has proven to be a water-based lubricant.

The machine element is preferably designed as a gearwheel or as a roller bearing component, in particular as a bearing ring or as a roller body. Such machine elements are in rolling contact with a counterpart and are therefore subject to an increased risk with regard to the shortening of the service life discussed at the beginning.

The use of a machine element according to the invention in a transmission has proven particularly useful. Use of a machine element according to the invention in a roller bearing, in particular a hybrid bearing, is also advantageous.

A hybrid construction is understood to mean that either the rolling elements or at least one of the bearing rings are formed from a ceramic material, at least one component in rolling contact with the ceramic material being a machine element according to the invention. The ceramic material can be, for example, silicon nitride, aluminum dioxide or sialons.

The use of a machine element according to the invention in a hydraulic unit, a hydraulic fluid being present as the water-based cooling lubricant, is also preferred. The hydraulic unit is in particular a pump.

Generally, a machine element is made of steel, which is hardened on its surface by nitriding at least in some areas and has a surface hardness of ≥ 650 HV 1 and a nitriding hardness depth (NHD) of ≥ 0.1 mm, the machine element being in contact with one in the area of nitriding water-based lubricant or a water-based cooling lubricant, each having a water content of ≥ 20% by weight, in particular in the range of ≥ 20% by weight to <50% by weight, is used, ideally with regard to the service life of the machine element. Such a machine element is preferably designed as a gearwheel or as a roller bearing component, in particular as a bearing ring or as a roller body.

• 1 ein Maschinenelement in Form eines Wälzlagerbauteils im Schnittbild;
• 2 ein Wälzlager im Halbschnitt mit zwei Maschinenelementen;
• 3 das Wälzlager aus 2 in dreidimensionaler Ansicht;
• 4 ein Getriebe mit Maschinenelementen in Form von Zahnrädern; und
• 5 ein Hydraulikaggregat in Form einer Pumpe mit Maschinenelementen.

The 1 to 5 are to explain machine elements according to the invention and their use by way of example. So shows:

• 1 a machine element in the form of a rolling bearing component in the sectional view;
• 2nd a half-section rolling bearing with two machine elements;
• 3rd the rolling bearing 2nd in three-dimensional view;
• 4th a gear with machine elements in the form of gears; and
• 5 a hydraulic unit in the form of a pump with machine elements.

1 shows a machine element 1 in the sectional view in the form of a rolling bearing component 1b , in particular in the form of a spherical rolling element 1b " . The machine element 1 is made of 31CrMoV9 nitriding steel and has been completely nitrided on the surface. The machine element 1 points as the core material 11 the nitriding steel 31CrMoV9 on the edge area 12 adjacent to a surface 13 of the machine element 1 in a nitriding depth NHD of 0.15 mm is embroidered. In contact with a surface 13 of the machine element 1 there is a water-based lubricant 2nd to lubricate it. The lubrication is said to cause abrasive wear on the surface 13 minimize.

2nd shows a rolling bearing 3rd in half cut in hybrid construction with two machine elements 1 in the form of bearing rings 1b ' made of nitrided steel and rolling elements 10th made of ceramic. The bearing rings 1b ' are nitrided in the area of their raceways and have a hardened edge area there 12 on. There is therefore only a partial nitriding of the surfaces 13 the bearing rings 1b ' in front. There is also a cage 6 recognizable. The space between the bearing rings 1b ' is with a water based lubricant 2nd filled.

3rd shows the rolling bearing 3rd out 2nd in three-dimensional view. The same reference numerals as in 2nd identify the same elements.

4th shows a transmission 4th with machine elements 1 in the form of gears 1a . The gears 1a are made of 32CrMoV13 steel and completely nitrided on the surface. The gear 4th is with a water based lubricant 2nd lubricated.

5 shows a hydraulic unit 5 in the form of a pump in longitudinal section with machine elements 1 , among other things in the form of bearing rings 1b ' and rolling elements 1b " made of nitriding steel with complete surface nitriding, in one housing 6 , which is a water-based cooling lubricant 2 ' includes.

Reference symbol list

1

Machine element

1a

gear

1b

Rolling bearing component

1b '

Bearing ring

1b "

Rolling elements

2nd

water-based lubricant

2 '

water-based coolant

3rd

roller bearing

4th

transmission

5

Hydraulic unit

6

casing

10th

Ceramic rolling elements

11

Core material

12

Edge area

13

surface

NHD

Depth of nitriding

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 101009039626 A1 [0004]

Claims (10)

Machine element (1) made of steel, which is at least partially hardened on its surface (13) by means of nitriding and has a surface hardness of ≥ 650 HV 1 and a nitriding hardness depth (NHD) of ≥ 0.1 mm, the machine element (1) being in the area the nitriding is lubricated by means of a water-based lubricant (2) or a water-based cooling lubricant (2 '), each having a water content of ≥ 20% by weight. Machine element (1) after Claim 1 , the steel being formed from nitrided steel. Machine element (1) after Claim 1 or Claim 2 , the steel being formed from 31CrMoV9 or 32CrMoV13. Machine element (1) according to one of the Claims 1 to 3rd , The machine element (1) being designed as a gearwheel (1a) or as a roller bearing component (1b), in particular as a bearing ring (1b ') or as a roller body (1b "). Use of a machine element (1) according to one of the Claims 1 to 4th in a gearbox (4). Use of a machine element (1) according to one of the Claims 1 to 4th in a roller bearing (3), in particular a roller bearing (3) in hybrid construction. Use of a machine element (1) according to one of the Claims 1 to 4th in a hydraulic unit (5), a hydraulic fluid being present as the water-based cooling lubricant (2 '). Use after Claim 7 , wherein the hydraulic unit (5) is a pump. Use of a machine element (1) made of steel, which is hardened on its surface (13) at least in regions by means of nitriding and has a surface hardness of ≥ 650 HV 1 and a nitriding depth (NHD) of ≥ 0.1 mm, the machine element (1) in the area of nitriding in contact with a water-based lubricant (2) or a water-based cooling lubricant (2 '), each having a water content of ≥ 20% by weight. Use after Claim 9 , The machine element (1) being designed as a gearwheel (1a) or as a roller bearing component (1b), in particular as a bearing ring (1b ') or as a roller body (1b ").

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