Mahle GmbH (Ed.) Cylinder Components: Properties, applications, materials

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3.5 Bearing materials 63

Descrip-

tion

Chemical composition of

the base alloy

[%]

Application/

properties

Process Minimum

hardness

(alloy/steel

back)

Specific

bearing

load

capacity

[MPa]

Design

Al Sn Si Cu other

MAS

84 10 4 2 Bearings;

high load

capacity with

high wear

resistance

Cast

aluminum

alloy hot

roll-plated

on steel

MAS 18:

65–70 HR 15T

55–74 HV

Steel:

60–96 HRB

110–210 HV

55 Bi-metal material with

fine precipitation of

the tin and silicon

phase in an aluminum

matrix, roll-plated

onto low-carbon steel

with a galvanically

applied intermediate

layer of nickel

MAS

89 6 2 1 Ni 1

0.26

0.16

Plain

bearings,

bushings, and

thrust was-

hers; medium

load capacity

with high

wear resi-

stance and

embedability

Cast alumi-

num alloy

roll-plated

on steel

MAS 19:

62–69 HR 15T

48–62 HV

Steel:

82–99 HRB

155–235 HV

60 Bi-metal material

with fine precipitation

of the tin phase

in an aluminum

matrix, combined

with an intermediate

aluminum layer and

roll-plated onto a low-

carbon steel back

MAS

89 6 2 1 Ni 1

0.25

0.16

Plain

bearings,

bushings,

and thrust

washers; high

load capacity

with high

wear resi-

stance and

embedability

Cast alumi-

num alloy

roll-plated

on steel

MAS 20:

65–72 HR 15T

55–65 HV

Steel:

82–99 HRB

155–235 HV

70 Bi-metal material with

fine precipitation of

the tin phase in an

aluminum matrix,

combined with an

intermediate AlMn/

AlSi layer and roll-

plated onto a low-

carbon steel back

MAS

84 10 4 2 Bearings;

high load

capacity with

high wear

resistance

Cast

aluminum

alloy hot

roll-plated

on steel

MAS 23:

72–80 HR 15T

75–90 HV

Steel:

70–98 HRB

125–230 HV

75 Bi-metal material with

fine precipitation of

the tin and silicon

phase in an aluminum

matrix, roll-plated

onto low-carbon steel

with a galvanically

applied intermediate

layer of nickel

MAS

83 15 2 Bearings;

high load

capacity with

high confor-

mability

Cast

aluminum

alloy hot

roll-plated

on steel

MAS 26:

65–75 HR 15T

60–70 HV

Steel:

70–98 HRB

125–230 HV

85 Bi-metal material

with aligned tin phase

in the aluminum

matrix, combined

with an intermediate

aluminum layer and

roll-plated onto a low-

carbon steel back

64 3 Bearings

Table 3.3: Alloys of cast bronze (overlays, see Table 3.6)

Descrip-

tion

Chemical composi-

tion of the base alloy

[%]

Application/

properties

Process Minimum

hardness

(alloy/steel

back)

Specific

bearing

load

capacity

[MPa]

Design

Cu Pb Sn other

MCB

78 20 2 Bearing material

for tri-metal

bearings

Lead-bronze

alloy cast on

steel

MCB 1:

66–88 HR 15T

80–190 HV

Steel:

68–87 HRB

121–172 HV

See upper

limit of

overlay

Bi-metal material,

copper-tin base

material, cast on

steel

MCB

75 23 2 Bearing material

for tri-metal

bearings

Lead-bronze

alloy cast on

steel

MCB 2:

max. 75 HR

15T

max. 95 HV

Steel:

63–99 HRB

115–230 HV

See upper

limit of

overlay

Bi-metal material,

copper-tin base

material, cast on

steel

MCB

80 10 10 Bearing material

for rod bushings

Lead-bronze

alloy cast on

steel

MCB 5:

75–88 HR 15T

95–160 HV

Steel:

43–97 HRB

90–215 HV

130 Bi-metal material,

copper-tin base

material, cast on

steel

MCB

96 4 Lead-free bea-

ring material for

tri-metal sputter

bearings

Lead-free

bronze cast

on steel

MCB 15:

70–92 HR 15T

90–145 HV

Steel:

80–100 HRB

150–240 HV

See upper

limit of

overlay

Bi-metal material,

copper-tin base

material, cast on

steel

MCB

96 4 Lead-free bea-

ring material for

tri-metal bearings

(sputter or HVOF

overlay)

Lead-free

bronze cast

on steel

MCB 16:

75–88 HR 15T

90–140 HV

Steel:

76–94 HRB

140–200 HV

See upper

limit of

overlay

Bi-metal material,

copper-tin base

material, cast on

steel

91 4 Bi 4

Ni 1

Lead-free bea-

ring material for

tri-metal bearings

with galvanically

applied overlay

Lead-free

bronze cast

on steel

MCB 17:

68–85 HR 15T

80–125 HV

Steel:

80–100 HRB

150–240 HV

See upper

limit of

overlay

Bi-metal material

with bismuth,

copper-tin base

material, cast on

steel

MCB

91 8 Ni 1 Lead-free bearing

material for rod

bushings

Lead-free

bronze cast

on steel

MCB 20:

75–88 HR 15T

90–140 HV

Steel:

53–85 HRB

100–165 HV

See upper

limit of

overlay

Bi-metal material,

copper-tin base

material, cast on

steel

3.5 Bearing materials 65

Table 3.4: Sin

tered bronze alloys

Descrip-

tion

Chemical composi-

tion of the base alloy

[%]

Application/

properties

Process Minimum

hardness

(alloy/steel

back)

Specific

bearing

load

capacity

[MPa]

Design

Cu Pb Sn other

MSB

80 10 10 Standard bronze for

bushings

Lead-bronze

alloy sintered

on steel

MSB 10:

60–85 HR 15T

60–145 HV

Steel:

55–85 HRB

100–165 HV

130 Bi-metal material

with consistently

formed lead phase,

copper-tin base

material, sintered

on steel

MSB

101

80 10 10 Bronze for bushings

sintered on hard

steel; niche appli-

cation for improved

press fit

Lead-bronze

alloy sintered

on hard

steel

MSB 101:

60–83 HR 15T

60–145 HV

Steel:

87–94 HRB

170–200 HV

130 Bi-metal material

with consistently

formed lead phase,

copper-tin base

material, sintered

on hard steel

MSB

91 8 Ni 1 Sintered lead-free

bronze bushings

with increased resi-

stance to corrosion

Lead-free

bronze alloy

sintered on

steel

MSB 20:

77–85 HR 15T

90–190 HV

Steel:

56–85 HRB

105–165 HV

150 Lead-free copper-

tin bi-metal

material, sintered

on steel

MSB

201

91 8 Ni 1 Sintered lead-free

tri-metal bearing

material, and for

lead-free bushings

on steel for incre-

ased resistance to

corrosion; niche

application for

improved press fit

Lead-free

bronze alloy

sintered on

hard steel

MSB 201:

77–85 HR 15T

90–190 HV

Steel:

87–94 HRB

170–200 HV

150 Lead-free copper-

tin bi-metal mate-

rial, sintered on

hard steel

Table 3.5: Wh

ite metal

Descrip-

tion

Chemical compo-

sition of the base

alloy

[%]

Application/

properties

Process Minimum

hardness

(alloy/steel)

Design

Pb Sb Sn As

L 23 83 15 1 1 Bushings for electric motors,

transmissions, compressors,

and automobile engines

Excellent embedability,

conformability

White metal

cast on steel

15 HB

2.5 / 15.6

25 / 30

50 HRB

90 HB

1/30

Bi-metal material, with

white metal cast on steel

66 3 Bearings

Table 3.6: Overlays

Descrip-

tion

Chemical composition of the

base alloy

[%]

Application/

properties

Process Specific

bearing

load

capacity

[MPa]

Design

Pb Sn Cu In Al other

P 3 87 10 3 1 Lead-based

overlay for less

demanding appli-

cations

Galvanic

application

70 Galvanically applied lead

layer with homogeneously

distributed copper-tin; with

intermediate nickel layer

P 5 85 10 5 Lead-based over-

lay with improved

wear resistance

Galvanic

application

75 Galvanically applied lead

layer with homogeneously

distributed copper-tin; with

intermediate nickel layer

P 9 78 13 9 Higher load capa-

city for overlays

containing lead

Galvanic

application

80 Galvanically applied lead

layer with homogeneously

distributed copper-tin; with

intermediate nickel layer

Q 1 92 8 High-performance

gasoline engines

Galvanic

application

85 Galvanically applied lead

layer with homogeneously

distributed indium

C 1 88 11 Al

Overlay with

increased wear

resistance for

passenger car

diesel engines

Galvanic

application

80 Galvanically applied lead

layer with homogeneously

distributed aluminum oxide

and local tin enrichment;

with intermediate nickel

layer

C 2 75 10 14 Al

Higher load

capacity and

wear resistance

for passenger car

diesel engines

Galvanic

application

90 Galvanically applied

lead-indium layer with

homogeneously distributed

aluminum oxide and local

tin enrichment; with inter-

mediate nickel layer

H 1 20 1 79 Thermally sprayed

lead-free coating

High velocity

oxygen fuel

spraying

(HVOF)

85 Thermally sprayed alu-

minum-copper layer with

homogeneously distributed

tin phase

S 1 40 1 59 Sputter overlay

for passenger car

diesel engines

Sputter 110 Sputter aluminum-copper

layer with fine homogene-

ously distributed tin phase;

with intermediate nickel-

chrome layer

S 2 30 1 69 Sputter overlay for

high-performance

passenger car

applications

Sputter 120 Sputter aluminum-copper

layer with fine homogene-

ously distributed tin phase;

with intermediate nickel-

chrome layer

S 3 40 1 59 High-performance

diesel engines for

passenger cars

Sputter min. 100 Sputter aluminum-copper

layer with fine homo-

genously distributed tin

phase, with intermediate

aluminum-tin layer

3.6 Market requirements and technology trends 67

Descrip-

tion

Chemical composition of the

base alloy

[%]

Application/

properties

Process Specific

bearing

load

capacity

[MPa]

Design

Pb Sn Cu In Al other

T 2 min.

Lead-free gal-

vanically applied

layer for high-load

applications

Galvanic

application

90 Galvanically applied tin

layer with fine-grained

structure; with intermediate

nickel layer

T 4 90 Ag 10 Lead-free gal-

vanically applied

layer for high-load

applications

Galvanic

application

95 Galvanically applied tin

layer with homogeneously

distributed tin-silver phase,

with intermediate nickel

layer

Table 3.7: Protec

tive coatings (RB: connecting rod bearing, MB: main bearing, BG: bushings)

Descrip-

tion

Chemical composition of the

base alloy

[%]

Application/properties Process

Pb Sn Cu Al

P 1 100 Used for BG surfaces

Oxidation resistance

Galvanic application

P 81 100 Used for RB and MB surfaces

Oxidation resistance

Galvanic application

3.6 Market requirements and technology trends

The goals of ongoing development of engines are higher performance, lower fuel consump-

tion, lower emissions, smaller designs, and lower costs. These result in increased demands

on MAHLE engine components in terms of wear resistance, capacity, and seizure resistance.

Table 3.8 shows a summary of the effects of these goals on the bearing portfolio.

68 3 Bearings

Table 3.8: Market demands and legal goals for engine components

Engine trends Effects on the opera-

ting characteristics of

the engine

Effects on bearings

1. Legal goals

Emissions and particle

reduction

Reduction of engine

friction

Lower oil viscosity Increased wear,

redesign

Reduction of engine

weight

Lighter components,

aluminum crankcases

Excessive housing

deformation

Gasoline direct

injection

Higher piston weight Increased inertial load

Exhaust gas

recirculation

Oil contamination Increased wear

Increase in peak

cylinder pressure

Greater mechanical

loads

Greater loads

Noise Less vibration Reinforced crankcases Reduced housing

deformation

Prohibited materials Lead-free components Lead-free materials

2. Customer demands

Higher performance Greater air consump-

tion and greater blow-

Higher temperatures

and engine speed

Overheating, higher

inertial loads

Increase in peak

cylinder pressure

Greater mechanical

loads

Greater loads

Lower fuel consump-

tion

Reduced engine

friction, downsizing

Lower oil viscosity Increased wear,

redesign

Reduction of engine

weight

Lighter components,

aluminum crankcases

Excessive housing

distortion

Gasoline direct

injection

Higher piston weight Increased inertial loads

Longer oil change

intervals

Oil contamination and

aging

Increased wear,

corrosion

Service life, reliability Higher vehicle miles

traveled

Redesign

To meet these demands, the bearings are adapted in terms of dimensions and materials.

High-strength aluminum alloys for bi-metal bearings are newly developed for this purpose.

New overlays for tri-metal bearings and lead-free materials as a substitute for the traditional

leaded bronze have also been introduced on the market.

4 Connecting rod

4.1 Introduction

The connecting rod connects the piston to the crankshaft, and consists of the crank or big

end, pin or small end, and shank.

The connecting rod small end, which is connected to the piston via the piston pin, transmits

the combustion pressure of the cylinder to a force on the crank pin. The crank pin is eccen-

tric to the rotational axis of the crankshaft, resulting in a moment force that induces a rotary

motion (Figure 4.1). The connecting rod is thus a mechanical element that transforms the

axial motion of the piston into the rotation of the crankshaft.

Figure 4.1:

Main motions of the piston-connecting rod

system

Vertical arrow: oscillating

Circular motion: rotating

The space covered by the connecting

rod during one revolution of the crank-

shaft, also known as the conrod sweep

(Figure 4.2), must be considered in col-

lision studies for the crankcase and

engine block.

While the small end bore is always closed,

the large bore is normally designed to

70 4 Connecting rod

come apart for assembly. Table 4.1 provides information about the different design details

of connecting rods, but not about the interrelationship of individual details. The task of the

designer is to determine the correct conﬁguration associated with the speciﬁcation.

Table 4.1: Types of connecting rods and design parameters

Area Type

Small end Parallel Stepped Trapezoidal

Piston pin (small end) Floating Fixed

Shank I-profile H-profile (motorsport)

Crank end Straight split Angle split

Parting plane of crank end Cracked Machined flat, with fit sleeve/

dowel screw/dowel pins

Tooth profile

Blank production Forging Casting Powdered metal/sintering

Figure 4.2:

Conrod sweep

4.1 Introduction 71

Figure 4.3: Terms and major dimensions of a connecting rod

Figure 4.3 shows the important terms and dimensions of a connecting rod.

72 4 Connecting rod

4.2 Stresses

As the element that transfers forces and motions between the piston and the crankshaft, the

connecting rod is subjected to large, alternating loads. The connecting rod is loaded in com-

pression (under prevailing gas pressure) and in tension (primarily due to inertia force). The

connecting rod is also stressed in bending due to its pivoting motion. As a moving engine

component, it should be as light as possible and sufﬁciently stiff. Sufﬁcient component and

structural strength must also be ensured.

The transmission of power from the piston and piston pin via the connecting rod to the

crankshaft is achieved by the lubrication in the bearings. The force applied to the connect-

ing rod is therefore dependent on the pressure distribution in the lubricant. This, in turn, is

affected by the stiffness of the connecting rod end bores. The inertia force is held in equilib-

rium by the lubrication pressure between the crank journal and the cap-side bearing hous-

ing. The joint integrity between the connecting rod and the cap is provided by the connecting

rod bolts. The connecting rod big end bore ovalizes under inertia force and the bolts are bent

outwards. If the bolt force is insufﬁcient, the connecting rod bolted joint will open towards the

crank journal pin side; see Figure 4.4.

Under maximum gas pressure, however, the connecting rod shank presses on the crank

journal via the hydrodynamic boundary layer. The connecting rod big end bore becomes

transversely ovalized and the bolts bend inward. Due to these deformations, considerable

bending stress occurs in the connecting rod end. The most highly stressed areas in straight-

split connecting rods, in addition to the bolt threads, are the ﬁllets on the transition from the

shank to the big end and to the small end. Angle-split connecting rods have the disadvan-

tage that the upper part of the blind hole thread is located directly in the path of greatest

stress (Figure 4.7).

Figure 4.4:

Horizontal close-in, bolt bending and

gap opening caused by inertia force