Klausur 3 August Sommersemester 2017, Fragen und Antworten PDF

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Summary

Institut für Eisenhüttenkunde
Department of Ferrous Metallurgy
Univ. Prof. Dr.-Ing. Wolfgang Bleck...

Description

Master examination „Steel Design“ 03.08.2017 Name, first name:

Matriculation number:

Declaration:

I am healthy and able to take part in the examination.

Signature:

Task

Points

1 2 3 4 5 6 7 8 9 10 11 12 13 14

3 6 4 4 4 2 4 1 3 4 5 3 3 4

Sum

50

You need 44% to pass the examination.

Achieved points

Points after review (additional points)

Steel Design Task 1

2 AHSS I

3 Point(s)

Using a light optical microscope, you compare three thin sheets: a mild steel, a DP-steel and a TRIP-steel. Sketch the observed microstructure, paying attention to the different grain sizes! Which phases can be observed in the microstructure of the three steel types? Give the approximate volume fractions. (3 Points)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design Task 2

3 AHSS II

6 Point(s)

a) Sketch the stress strain curves of the following steels in the given diagram (figure 1): (i) a DP-Steel and (ii) HSLA-Steel (without temper rolling). Explain the individual

Stress / Spannung

material behavior of the steels. (4 Points)

Strain / Dehnung Figure 1

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design

4

b) What is the influence of the following factors on the ultimate tensile strength of DPSteels? (1.5 Points) i)

A larger martensite volume fraction

ii)

A larger ferrite grain size

iii)

A higher carbon content in martensite

c) Is there any influence of the martensite island diameter on the mechanical properties of DP-steels? Explain your answer briefly. (0.5 Points)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design Task 3

5 AHSS III

4 Point(s)

Dual phase steels typically have a structure with 5 to 30 Vol .-% martensite. Explain the upper and lower limits based on microstructure-property correlations. (4 Points)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design

6

Task 4

AHSS IV

4 Point(s

The special properties of TRIP-steels are related to the presence of retained austenite in the microstructure. a)

How is it possible to have retained austenite stable in a 0.2 wt.-% C steel? Explain your answer briefly. (2 Points)

b)

Is the retained austenite thermodynamically and/or mechanically stable? (2 Points)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design

7

Task 5

deep drawing steel I

3 Point(s)

A characteristic indicator for the deep drawing ability of a steel is the r-value. a)

Describe the meaning of the r-value. (2 Points)

b)

Describe the formula for r-value calculation. (1 Point)

c)

Tensile tests have been performed for two different materials (A and B). For Material A the r-value corresponds to 1.4, whereas the r-value for Material B is 2.3. Which material is more suitable for deepdrawing applications in the automotive industry? (1 Point)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design Task 6

8 deep drawing steel II

2 Point(s)

Deep drawing steels are separated into two types. The microstructures for both types are shown in figure 1. a)

Which type is visible in figure 1a), which in figure 1 b)? (1 Point)

Figure 1: Micrographs of microstructure of two deepdrawing steels

b)

Describe briefly the characteristics of both microstructures. (1 Point)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design Task 7 a)

9 pipe manufacturing I

4 Point(s)

What is the name of the first basic processing step used in the production of seamless tubes broadly? (1 Point)

b)

Name three typical processing unit or techniques, which are used in the following process step (stretch forming). (3 Points)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design

10

Task 8

pipe manufacturing II

1 Point(s)

What is the most commonly used welding process for welded pipe without using welding filler material? (1 Point)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design Task 9

11 Oil Country Tubular Goods (OCTG)

3 Point(s)

What is the most important aspect in improving the corrosion resistance to sour gas in high strength quenched and tempered steels for oil pipes from materials science point of view? (3 Points)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design

12

Task 10 a)

precision tubes

4 Point(s)

What is the purpose of an “Autofrettage” treatment and how does this treatment affect the microstructure of the steel? (2 Points)

b)

For which components is the “Autofrettage” treatment necessary? Explain your answer briefly (2 Points)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design Task 11

13 line pipes

5 Point(s)

a)

Name two media, which are typically transported with line pipes? (1 Point)

b)

What are the requirements of the application areas on line pipes? Name at least two environmental conditions and explain the resulting requirements for the material. (2 Points)

c)

What is the problem with media with an increased H2S content? Explain the relevant chemical components and name the damage mechanisms. (2 Points)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design

14

Task 12

special alloyed steels

3 Point(s)

Stainless steels can be separated into different groups based on their microstructure. Complete table 1 with the microstructures of the stainless steels. (3 Points) Table 1 Microstructure

Head of Department: E-Mail:

C

Cr

Mo

Ni

0,01 –

16,5 –

0,1 –

8,0 –

0,03

21,0

5,0

26,0

0,01 –

21,0 –

0,1 –

4,5 –

0,05

28,0

5,0

8,0

0,06 -

12,0 –

0,1 –

0–

1,10

17,0

2,0

2,5

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Cu

N

other

0,02 –

Ti/Nb:

0,25

5/10 x C

0,1 –

0,05 –

W: 0 –

3,5

0,30

1,0

-

-

-

0 – 2,0

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design Task 13 a)

15 rail steels

3 Point(s)

The mechanical properties of some rail steels are improved with head-hardening. How does this treatment affect the final microstructure ? (1 Point)

b)

Talking about rails, there are two factors that determine the service lifetime, according to the field of application. Name both factors and explain what leads to their occurrence. Give an example for the fields of application they are used for. (2 Points)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224

Steel Design Task 14

16 tool steels

4 Point(s)

Tool steels are usually quenched and tempered. a)

Name at least 2 reasons why tool steels are tempered. (2 Points)

b)

What should be considered according to the tempering temperature? (1 Point)

c)

Give a short explanation why tool steels are tempered several times instead of tempering them once for a long time. (1 Point)

Head of Department: E-Mail:

Univ. Prof. Dr.-Ing. W. Bleck [email protected]

Fon: +49 241 8095782 Fax: +49 241 8092224...