Weight Reduction Opportunities in

Bolted Joints

Mexico Fastener Fair 2017

Material & Design Considerations

Mark Mahaffy

Yair Diaz

Motivation – CO2 Regulations

2010 2015 2020 2025

170

190

210

100

130

150

110

90

180

220

200

160

120

140

CO

2-E

mis

sio

ne

n in

NE

FZ

-

Äq

uiv

ale

nte

n [g

CO

2/k

m]

Empirical Daten1 Target values

Gültige Grenzwerte

Offizielle Vorschläge

1IC

CT

(2014),

D

OT

(2011),

M

ET

I (2

011)

Global Comparison CO2-limits

Emission regulations

Kxtreme – Ultra High Tensile Fasteners

KXtreme® - Overview, Property Classes & Target Applications

Ultra High Tensile Standards

15.10.2015 5

- Ultrafeste Schrauben sind bis

Festigkeitsklasse 16.8 in VDA 235-205

und USCAR Guide UHSFG-1416U-2014

beschrieben. Diese Schrauben müssen

ein bainitisches Gefüge aufweisen.

Two relevant standards Description

Conventional high strength bolts are described up to property class 12.9 in ISO 898-1. These bolts must demonstrate a martensitic microstructure.

(c) KAMAX Automotive GmbH – confidential – technical data may be subject to change

KXtreme® Property Classes

Ch

as

sis

E

ng

ine

KXtreme

Chassis

Property Class

Tensile Strength [Mpa]

Yield Strength [Mpa]

Application

Coating

KXtreme

Engine 16 17

Property Class 14.8U 14.9U 15.8U 15.9U 16.8U 17.8U

Tensile Strength [Mpa] 1400 - 1550 1400 - 1550 1500 - 1650 1500 - 1650 1600 - 1750 1700 - 1850

Yield Strength [Mpa] ≥ 1200 ≥ 1340 ≥ 1290 ≥ 1430 ≥ 1400 ≥ 1450

Application

Coating

Ultrahigh strength fasteners for engine internal applications (Downsizing, Uprating)

KAPHOS® N / KAPHOS® L / polymeric coatings / oil treatment

Engine external applications and Chassis applications

Zinc Nickel / Zincflake

14 15

1250 - 1400 1400 - 1550 1500 - 1650

≥ 1180 ≥ 1340 ≥ 1430

12 14 15

12.9U 14.9U 15.9U

1.200

1.000

0

800

1.600

1.800

1.400

1.040

KXtreme - Engine

1.700 1.600

1.400

KXtreme - Chassis

1.500

Te

nsile

str

ength

[M

Pa] 1.500

1.400

1.220

ISO 898-1

1.040

800 16.8U

12.9U

17.8U

10.9

8.8

15.9U /15.8 U

14.9U

Property Class 14 15 16 17

Subcategory/ Designation 14.8U 14.9U 15.8U 15.9U 16.8U 17.8U

Tensile Strength Rm [MPa] 1) 1,400 – 1,550 1,500 – 1,650 1,600 – 1,750 1,700 – 1,850

Yield Strength Rp0,2 [MPa] 1)

≥

1,200

≥

1,340

≥

1,290

≥

1,430

≥

1,380

≥

1,450

Yield to Tensile Strength

Ratio Rp0,2/Rm 2)

~

0.86

~

0.96

~

0.86

~

0.95

~

0.86

~

0.86

Fracture elongation A5 2) ≥ 10% ≥ 9% ≥ 8% ≥ 8%

Necking Z 2) ≥ 50% ≥ 48% ≥ 46% ≥ 46%

KXtreme Mechanical Property Table

15.10.2015 7

1) Strength values measured on standard specimens 2) Ductility values (Toughness) on standard specimens

Subject to technical changes

(c) KAMAX Automotive GmbH – confidential – technical data may be subject to change

Downsizing Potential

Torque controlled

Torque and angle

controlled

(yield controlled )

KXtreme® 15.9U allows downsizing to the next smaller bolt dimension

Comparison of 10.9 vs 15.9U fasteners at different sizes

UHT Heat Treat Process

15.10.2015 9

Time

Tem

pera

ture

Ac3

RT

Tempering

Austenitizing Conventional

Heat Treatment

(Q&T)

UHT: Bainitic

Austempering

Ms

Isothermic transformation

Oven Salt bath Washing / Drying

Oven Oil bath Water bath Oven

UHT

Standard

Description Bainitic austempering DIN EN 10052

Fundamental difference to

martensitic tempering is

the quenching and

holding at a temperature

greater than the

martensite start

temperature (Ms)

(c) KAMAX Automotive GmbH – confidential – technical data may be subject to change

KAMAX UHT – No Design Limitations up to M22

Bolt lengths, shapes Head types

All current head shapes

All current bolt lengths, thread

types and external shapes (center

collar, grooves)

03.11.2015 (c) KAMAX Automotive GmbH – confidential – technical data may be subject to change 10

UHT Summary

19.06.2017 11

Up to property 17.8U

Bainitic Microstructure

No size limitation

Engine Applications:

Production up to PC17.8U

Connecting Rod Bolts

Cylinder Head Bolts

Bearing Cap Bolts

Fly Wheel Bolts

Damper Bolts

Chassis Applications

PC12.8U in Production

PC14.8U first applications in customer

testing. Production July 2017.

Using selected material and special

processing data shows risk for hydrogen

induced failure is similar to PC10.9

System cost & weight savings when designed

up front

KXtreme

(c) KAMAX Automotive GmbH – confidential – technical data may be subject to change

KX – Lightweight Bolt

T. Schmitt

M. Kellner

Weight Reduction & Increased Function

Weight Reduction

19.06.2017 13

Head weight reduction up to 34%

Inner Hex Extrusion adds Value to the Weight Reduction

• Hex flange head and internal

hex drive are adjusted to the

next standard size

(c) KAMAX Automotive GmbH – confidential – technical data may be subject to change

Results

All specimens fail in threaded section.

Lightweight-head has no negative impact on the ultimate tensile strength.

Wedge Tensile Results

19.06.2017 14

Wedge Tensile Test (10°)

• According to DIN EN ISO 898

10°

Elongation [%]

Tensio

n [

MP

a]

(c) KAMAX Automotive GmbH – confidential – technical data may be subject to change

Lightweight Bolt Summary

19.06.2017 15

Reduction of head weight up to 34 %.

Additional functionality through internal hex

drive.

Non proprietary design, no patent required.

Possible application to every size and head

shape.

Lightweight head is independent of shaft and

thread length.

Available with all coating systems.

Selected as lightweight head for 2 global

automotive OEMs

KX - Lightweight Bolt

(c) KAMAX Automotive GmbH – confidential – technical data may be subject to change

KXact – Precision Clamp Load

33.362%

52.462%

14.138%

Typical Clamp Load Variation Contributors

19.06.2017 (c) KAMAX Automotive GmbH – confidential – technical data may be subject to change 17

Tightening angle 𝜗

Cla

mp

lo

ad

FM

FM, min

FM, max

ΔFM

Factors of influence*

Thread tolerance

Tensile strength tolerance

Friction window

* Averaged for M6 – M20 u. 8.8 – 16.8

∆𝐹𝑀 =𝐹𝑀,𝑚𝑎𝑥−𝐹𝑀,𝑚𝑖𝑛

𝐹𝑀,𝑚𝑖𝑛 [%]

KAMAX Optimized Bolt

19.06.2017 (c) KAMAX Automotive GmbH – confidential – technical data may be subject to change 18

Example M12x1.75 10.9

0%

5%

10%

15%

20%

25%

30%

Stand der Technik KX-Vorspannkraftoptimierte Schraube

Cla

mp

load

sp

read

Gewindetoleranzen Vergütungsstreuung Reibwertfenster

13%

56%

31%

9%

18%

14%

Clamp load spread

reduced by 59%

Thread tolerance Current: 6g

Optimized for reduced clamp load

spread: 4g

Tensile strength tolerance Current: 1040-1190 MPa

Optimzed for reduced clamp load

spread: 50 MPa

Friction window Current: Δµ = 0.06

Optimzed for reduced clamp load

spread: Δµ = 0.03

Thread tolerance Tensile strength

tolerance Friction window

Current PC 10.9 bolt KX optimized bolt

Reduced Clamp Load Variation

19.06.2017 (c) KAMAX Automotive GmbH – confidential – technical data may be subject to change 19

Reduced: tensile strength tolerance + thread tolerance + friction window Tensile strength: 50 MPa

Thread tolerance: DIN13 / KN5602 / 4g

Friction window: Δµ = 0.03

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

M6x1 4g M8x1,25 4g M10x1,5 4g M12x1,75 4g M16x2 4g M20x2,5 4g

Cla

mp

lo

ad

vari

ati

on

16.8

14.8

12.9

10.9

8.8

Summary

19.06.2017 (c) KAMAX Automotive GmbH – confidential – technical data may be subject to change 20

Precise installation of clamp load

For special applications a clamp load

spread of ± 5 % possible

Light weight potential due to reduced max.

loads and reduced surface pressure.

For applications with narrow clamp load

requirements

Tightening angle 𝜗

Cla

mp

lo

ad

FM