自动翻译工具金属热处理外文文献及翻译

2021年1月19日发(作者：文化参赞)


原文

Heat

treatment

of

metal



The

generally

accepted

definition

for

heat

treating

metals

and

metal

alloys

is

“
heating

and

cooling

a

solid

metal

or

alloy

in

a

way

so

as

to

obtain

specific

conditions

or

properties.
”

Heating

for

the

sole

purpose

of

hot

working

(as

in

forging

operations)

is

excluded

from

this

definition
．
Likewise
，
the

types

of

heat

treatment

that

are

sometimes

used

for

products

such

as

glass

or

plastics

are

also

excluded

from

coverage

by

this

definition
．

Transformation

Curves

The

basis

for

heat

treatment

is

the

time- temperature-transformation

curves

or

TTT

curves

where
，
in

a

single

diagram

all

the

three

parameters

are

plotted
．
Because

of

the

shape

of

the

curves
，
they

are

also

sometimes

called

C-curves

or

S-curves
．

To

plot

TTT

curves
，
the

particular

steel

is

held

at

a

given

temperature

and

the

structure

is

examined

at

predetermined

intervals

to

record

the

amount

of

transformation

taken

place
．
It

is

known

that

the

eutectoid

steel

(T80)

under

equilibrium

conditions

contains
，
all

austenite

above

723
℃，

whereas

below
，
it

is

the

pearlite
．
To

form

pearlite
，
the

carbon

atoms

should

diffuse

to

form

cementite
．
The

diffusion

being

a

rate

process
，
would

require

sufficient

time

for

complete

transformation

of

austenite

to

pearlite
．
From

different

samples
，
it

is

possible

to

note

the

amount

of

the

transformation

taking

place

at

any

temperature
．
These

points

are

then

plotted

on

a

graph

with

time

and

temperature

as

the

axes
．
Through

these

points
，
transformation

curves

can

be

plotted

as

shown

in

Fig.1

for

eutectoid

steel
．
The

curve

at

extreme

left

represents

the

time

required

for

the

transformation

of

austenite

to

pearlite

to

start

at

any

given

temperature
．
Similarly
，
the

curve

at

extreme

right

represents

the

time

required

for

completing

the

transformation
．
Between

the

two

curves

are

the

points

representing

partial

transformation.

The

horizontal

lines

Ms

and

Mf

represent

the

start

and

finish

of

martensitic

transformation.

Classification

of

Heat

Treating

Processes

In

some

instances
，
heat

treatment

procedures

are

clear-cut

in

terms

of

technique

and

application
．
whereas

in

other

instances
，
descriptions

or

simple

explanations

are

insufficient

because

the

same

technique

frequently

may

be

used

to

obtain

different

objectives
．
For

example,

stress

relieving

and

tempering

are

often

accomplished

with

the

same

equipment

and

by

use

of

identical

time

and

temperature

cycles
．
The

objectives
，
however
，
are

different

for

the

two

processes
．



The

following

descriptions

of

the

principal

heat

treating

processes

are

generally

arranged

according

to

their

interrelationships
．

Normalizing

consists

of

heating

a

ferrous

alloy

to

a

suitable

temperature

(usually

50
°
F

to

100
°
F

or

28
℃

to

56
℃
)

above

its

specific

upper

transformation

temperature
．
This

is

followed

by

cooling

in

still

air

to

at

least

some

temperature

well

below

its

transformation

temperature

range
．
For

low-carbon

steels,

the

resulting

structure

and

properties

are

the

same

as

those

achieved

by

full

annealing
；
for

most

ferrous

alloys,

normalizing

and

annealing

are

not

synonymous.

Normalizing

usually

is

used

as

a

conditioning

treatment,

notably

for

refining

the

grains

of

steels

that

have

been

subjected

to

high

temperatures

for

forging

or

other

hot

working

operations.

The

normalizing

process

usually

is

succeeded

by

another

heat

treating

operation

such

as

austenitizing

for

hardening,

annealing,

or

tempering.

Annealing

is

a

generic

term

denoting

a

heat

treatment

that

consists

of

heating

to

and

holding

at

a

suitable

temperature

followed

by

cooling

at

a

suitable

rate.

It

is

used

primarily

to

soften

metallic

materials,

but

also

to

simultaneously

produce

desired

changes

in

other

properties

or

in

microstructure.

The

purpose

of

such

changes

may

be,

but

is

not

confined

to,

improvement

of

machinability,

facilitation

of

cold

work

(known

as

in- process

annealing),

improvement

of

mechanical

or

electrical

properties,

or

to

increase

dimensional

stability.

When

applied

solely

to

relive

stresses,

it

commonly

is

called

stress-relief

annealing,

synonymous

with

stress

relieving.

When

the

term

“
annealing
”

is

applied

to

ferrous

alloys

without

qualification,

full

annealing

is

applied.

This

is

achieved

by

heating

above

the

alloy
’
s

transformation

temperature,

then

applying

a

cooling

cycle

which

provides

maximum

softness.

This

cycle

may

vary

widely,

depending

on

composition

and

characteristics

of

the

specific

alloy.

Quenching

is

a

rapid

cooling

of

a

steel

or

alloy

from

the

austenitizing

temperature

by

immersing

the

work

piece

in

a

liquid

or

gaseous

medium.

Quenching

medium

commonly

used

include

water,

5%

brine,

5%

caustic

in

an

aqueous

solution,

oil,

polymer

solutions,

or

gas

(usually

air

or

nitrogen).

Selection

of

a

quenching

medium

depends

largely

on

the

hardenability

of

material

and

the

mass

of

the

material

being

treating

(principally

section

thickness).

The

cooling

capabilities

of

the

above-listed

quenching

media

vary

greatly.

In

selecting

a

quenching

medium,

it

is

best

to

avoid

a

solution

that

has

more

cooling

power

than

is

needed

to

achieve

the

results,

thus

minimizing

the

possibility

of

cracking

and

warp

of

the

parts

being

treated.

Modifications

of

the

term

quenching

include

direct

quenching,

fog

quenching,

hot

quenching,

interrupted

quenching,

selective

quenching,

spray

quenching,

and

time

quenching.


Tempering.

In

heat

treating

of

ferrous

alloys,

tempering

consists

of

reheating

the

austenitized

and

quench-hardened

steel

or

iron

to

some

preselected

temperature

that

is

below

the

lower

transformation

temperature

(generally

below

1300

℃

or

705

℃

).

Tempering

offers

a

means

of

obtaining

various

combinations

of

mechanical

properties.

Tempering

temperatures

used

for

hardened

steels

are

often

no

higher

than

300

℃
(150

℃
).

The

term

“
tempering
”

should

not

be

confused

with

either

process

annealing

or

stress

relieving.

Even

though

time

and

temperature

cycles

for

the

three

processes

may

be

the

same,

the

conditions

of

the

materials

being

processed

and

the

objectives

may

be

different.

Stress

relieving.

Like

tempering,

stress

relieving

is

always

done

by

heating

to

some

temperature

below

the

lower

transformation

temperature

for

steels

and

irons.

For

nonferrous

metals,

the

temperature

may

vary

from

slightly

above

room

temperature

to

several

hundred

degrees,

depending

on

the

alloy

and

the

amount

of

stress

relief

that

is

desired.

The

primary

purpose

of

stress

relieving

is

to

relieve

stresses

that

have

been

imparted

to

the

workpiece

from

such

processes

as

forming,

rolling,

machining

or

welding.

The

usual

procedure

is

to

heat

workpiece

to

the

pre- established

temperature

long

enough

to

reduce

the

residual

stresses

(this

is

a

time- and

temperature-dependent

operation)

to

an

acceptable

level;

this

is

followed

by

cooling

at

a

relatively

slow

rate

to

avoid

creation

of

new

stresses.

The

generally

accepted

definition

for

heat

treating

metals

and

metal

alloys

is

“
heating

and

cooling

a

solid

metal

or

alloy

in

a

way

so

as

to

obtain

specific

conditions

or

properties.
”

Heating

for

the

sole

purpose

of

hot

working

(as

in

forging

operations)

is

excluded

from

this

definition
．
Likewise
，
the

types

of

heat

treatment

that

are

sometimes

used

for

products

such

as

glass

or

plastics

are

also

excluded

from

coverage

by

this

definition
．

Transformation

Curves

The

basis

for

heat

treatment

is

the

time- temperature-transformation

curves

or

TTT

curves

where
，
in

a

single

diagram

all

the

three

parameters

are

plotted
．
Because

of

the

shape

of

the

curves
，
they

are

also

sometimes

called

C-curves

or

S-curves
．

To

plot

TTT

curves
，
the

particular

steel

is

held

at

a

given

temperature

and

the

structure

is

examined

at

predetermined

intervals

to

record

the

amount

of

transformation

taken

place
．
It

is

known

that

the

eutectoid

steel

(T80)

under

equilibrium

conditions

contains
，
all

austenite

above

723
℃，

whereas

below
，
it

is

pearlite
．
To

form

pearlite
，
the

carbon

atoms

should

diffuse

to

form

cementite
．
The

diffusion

being

a

rate

process
，
would

require

sufficient

time

for

complete

transformation

of

austenite

to

pearlite
．
From

different

samples
，
it

is

possible

to

note

the

amount

of

the

transformation

taking

place

at

any

temperature
．
These

points

are

then

plotted

on

a

graph

with

time

and


temperature

as

the

axes
．
Through

these

points
，
transformation

curves

can

be

plotted

as

shown

in

Fig.1

for

eutectoid

steel
．
The

curve

at

extreme

left

represents

the

time

required

for

the

transformation

of

austenite

to

pearlite

to

start

at

any

given

temperature
．
Similarly
，
the

curve

at

extreme

right

represents

the

time

required

for

completing

the

transformation
．
Between

the

two

curves

are

the

points

representing

partial

transformation.

The

horizontal

lines

Ms

and

Mf

represent

the

start

and

finish

of

martensitic

transformation.

Classification

of

Heat

Treating

Processes

In

some

instances
，
heat

treatment

procedures

are

clear-cut

in

terms

of

technique

and

application
．
whereas

in

other

instances
，
descriptions

or

simple

explanations

are

insufficient

because

the

same

technique

frequently

may

be

used

to

obtain

different

objectives
．
For

example,

stress

relieving

and

tempering

are

often

accomplished

with

the

same

equipment

and

by

use

of

identical

time

and

temperature

cycles
．
The

objectives
，
however
，
are

different

for

the

two

processes
．

The

following

descriptions

of

the

principal

heat

treating

processes

are

generally

arranged

according

to

their

interrelationships
．

Normalizing

consists

of

heating

a

ferrous

alloy

to

a

suitable

temperature

(usually

50
°
F

to

100
°
F

or

28
℃

to

56
℃
)

above

its

specific

upper

transformation

temperature
．
This

is

followed

by

cooling

in

still

air

to

at

least

some

temperature

well

below

its

transformation

temperature

range
．
For

low-carbon

steels,

the

resulting

structure

and

properties

are

the

same

as

those

achieved

by

full

annealing
；
for

most

ferrous

alloys,

normalizing

and

annealing

are

not

synonymous.

Normalizing

usually

is

used

as

a

conditioning

treatment,

notably

for

refining

the

grains

of

steels

that

have

been

subjected

to

high

temperatures

for

forging

or

other

hot

working

operations.

The

normalizing

process

usually

is

succeeded

by

another

heat

treating

operation

such

as

austenitizing

for

hardening,

annealing,

or

tempering.

Annealing

is

a

generic

term

denoting

a

heat

treatment

that

consists

of

heating

to

and

holding

at

a

suitable

temperature

followed

by

cooling

at

a

suitable

rate.

It

is

used

primarily

to

soften

metallic

materials,

but

also

to

simultaneously

produce

desired

changes

in

other

properties

or

in

microstructure.

The

purpose

of

such

changes

may

be,

but

is

not

confined

to,

improvement

of

machinability,

facilitation

of

cold

work

(known

as

in- process

annealing),

improvement

of

mechanical

or

electrical

properties,

or

to

increase

dimensional

stability.

When

applied

solely

to

relive

stresses,

it

commonly

is

called

stress-relief

annealing,

synonymous

with

stress

relieving.

When

the

term

“
annealing
”

is

applied

to

ferrous

alloys

without

qualification,

full

annealing

is

applied.

This

is

achieved

by

heating

above

the

alloy
’
s

transformation

temperature,

then

applying

a


cooling

cycle

which

provides

maximum

softness.

This

cycle

may

vary

widely,

depending

on

composition

and

characteristics

of

the

specific

alloy.

Quenching

is

a

rapid

cooling

of

a

steel

or

alloy

from

the

austenitizing

temperature

by

immersing

the

workpiece

in

a

liquid

or

gaseous

medium.

Quenching

medium

commonly

used

include

water,

5%

brine,

5%

caustic

in

an

aqueous

solution,

oil,

polymer

solutions,

or

gas

(usually

air

or

nitrogen).

Selection

of

a

quenching

medium

depends

largely

on

the

hardenability

of

material

and

the

mass

of

the

material

being

treating

(principally

section

thickness).

The

cooling

capabilities

of

the

above-listed

quenching

media

vary

greatly.

In

selecting

a

quenching

medium,

it

is

best

to

avoid

a

solution

that

has

more

cooling

power

than

is

needed

to

achieve

the

results,

thus

minimizing

the

possibility

of

cracking

and

warp

of

the

parts

being

treated.

Modifications

of

the

term

quenching

include

direct

quenching,

fog

quenching,

hot

quenching,

interrupted

quenching,

selective

quenching,

spray

quenching,

and

time

quenching.

Tempering.

In

heat

treating

of

ferrous

alloys,

tempering

consists

of

reheating

the

austenitized

and

quench-hardened

steel

or

iron

to

some

preselected

temperature

that

is

below

the

lower

transformation

temperature

(generally

below

1300

℃

or

705

℃
).

Tempering

offers

a

means

of

obtaining

various

combinations

of

mechanical

properties.

Tempering

temperatures

used

for

hardened

steels

are

often

no

higher

than

300

℃
(150

℃
).

The

term

“
tempering
”

should

not

be

confused

with

either

process

annealing

or

stress

relieving.

Even

though

time

and

temperature

cycles

for

the

three

processes

may

be

the

same,

the

conditions

of

the

materials

being

processed

and

the

objectives

may

be

different.

Stress

relieving.

Like

tempering,

stress

relieving

is

always

done

by

heating

to

some

temperature

below

the

lower

transformation

temperature

for

steels

and

irons.

For

nonferrous

metals,

the

temperature

may

vary

from

slightly

above

room

temperature

to

several

hundred

degrees,

depending

on

the

alloy

and

the

amount

of

stress

relief

that

is

desired.

The

primary

purpose

of

stress

relieving

is

to

relieve

stresses

that

have

been

imparted

to

the

workpiece

from

such

processes

as

forming,

rolling,

machining

or

welding.

The

usual

procedure

is

to

heat

workpiece

to

the

pre- established

temperature

long

enough

to

reduce

the

residual

stresses

(this

is

a

time- and

temperature-dependent

operation)

to

an

acceptable

level;

this

is

followed

by

cooling

at

a

relatively

slow

rate

to

avoid

creation

of

new

stresses.



The

generally

accepted

definition

for

heat

treating

metals

and

metal

alloys

is

“
heating

and

cooling

a

solid

metal

or

alloy

in

a

way

so

as

to

obtain

specific

conditions

or

properties.
”

Heating

for

the

sole

purpose

of

hot

working

(as

in

forging

operations)

is

excluded

from

this

definition
．
Likewise
，
the

types