INDIVIDUAL PROJECT
Material Science Institute
University of Washington

July 7-23, 1997

The Tempering of Tool Steels

by
Jim Shimel

 

Project Introduction and Concept

 

The world of manufacturing has over 150 types of tool steel available to be used in a wide range of applications. The American Iron and Steel Institute (AISI) has divided these into ten main groups:

Group AISI Designation
Water Hardening

W
Shock Resisting

S
Oil Hardening

O
Cold Work (Medium alloy, Air hardening)

A
Cold Work (High Carbon, High Chromium)

D
Hot Work (Chromium base, Tungsten base, Molybdenum base)

H
High Speed (Tungsten base)

T
High Speed (Molybdenum base)

M
Special Purpose (Low alloy)

L
Mold

P

 

The following procedure is used in the hardening and tempering process:

The technological system involved for the heat treating of these steels say to heat them to (50F to 100F) just above the upper critical temperature (somewhere between 1450F to 2250F) for each type of steel and quench in a solution of water, brine, oil or air cool. At this point the steel is at or near its maximum hardness which makes it too brittle for must things.

The steel needs to be reheated to a temperature slightly below the lower critical temperature and requench the steel.

Goal

The goal of this project is to recognize the six main colors used in tempering.

Light straw 425F

Dark straw 465F

Yellowish brown 490F

Purple 525F

Violet 545F

Pale Blue 590F

 

Objectives

  1. Define the following:

Hardness

Quenching

Tempering

Brittle

2. List and recognize the six tempering colors and their temperature.

 

Activity

Work hand out sheet before demonstration. Demonstration of these temperatures for tempering.

Equipment and Supplies

Hot plate

Pliers

Gloves

Can of Water

8 pieces of ¼ in. dia X6 in. long AISI O 1 (polished)

Safety Glasses

Procedure

  1. Place 7 pieces of AISI O1 on hot plate
  2. Heat hot plate to 425F(218C), when rods turn to light straw color, take one off and quench in water.
  3. Heat hot plate to 465F(241C), when rods turn to dark straw color, take one off and quench in water.
  4. Repeat the procedures in step 2 and 3 for 490F(254C), 525F(274C), 545F(285C), and 590F(310C).
  5. Heat the last piece up to 700F(371C) and quench(look at the color of the material).

 

Worksheet

Define:

Hardness_________________________________________________________________

Quenching________________________________________________________________

Tempering________________________________________________________________

Brittle____________________________________________________________________

 

 

 

AISI

TYPE

COMPOSITION %

HARDNING

TEMPERATURE in DEGRESS F

R/C

Desired

R/C

TEMPERING

TEMPERATURE

COLOR

W1

.6 to 1.4 C

1475

67

58

550

  

S5

.55C .4Mo .8Mn 2.S

1575

62

56

500

  

S7

.5C 1.4Mo 3.25Cr

1550

63

58

525

  

O1

.9C .5W .5Cr 1. Mn

1475

66

62

425

  

O6

1.45C .25Mo .8Mn 1.Si

1525

67

58

575

  

A2

1.C 1.Mo 5.Cr 1.V

1800

66

58

600

  

A6

.7C 1.25Mo 1.Cr 2.Mn

1550

62

59

400

  

D2

1.5C 1.Mo 12.Cr 1.V

1825

62

60

450

  

D5

1.5C 1.Mo 12.Cr 3.Co

1800

64

58

625

  

H19

.4C 4.5W 4.5Cr 2.V 4.25Co

          

H26

.5C 18.W 4.Cr 1.V

          

H42

.6C 6.W 5.Mo 4.Cr 2.V

          

T1

.75C 18.W 4.Cr 1.V

          

T6

.8C 20W 4.5Cr 1.5V 12.Co

          

M1

.85C 1.5W 8.5Mo 4.Cr 1.V

2200

65

60

1100

  

M44

1.15C 5.25W 6.25Mo 4.25Cr 2.V 12.Co

          

L6

.7C .25Mo .75Cr 1.5Ni

          

P21

.2C 4.Ni 1.2Al

          

 

A list of the elements and their symbols:

Carbon = C

Tungsten = W

Molybdenum = Mo

Chromium =Cr

Vanadium = V

Manganese = Mn

Cobalt = Co

Nickel = Ni

Aluminum = Al

Word 97 doc file of this project:  shimel.doc

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