CN106755798A - Heat treatment normalizing process - Google Patents
Heat treatment normalizing process Download PDFInfo
- Publication number
- CN106755798A CN106755798A CN201510800813.3A CN201510800813A CN106755798A CN 106755798 A CN106755798 A CN 106755798A CN 201510800813 A CN201510800813 A CN 201510800813A CN 106755798 A CN106755798 A CN 106755798A
- Authority
- CN
- China
- Prior art keywords
- temperature
- normalizing
- hardness
- 26hrc
- 40crh
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/28—Normalising
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/002—Heat treatment of ferrous alloys containing Cr
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention discloses a kind of suitable for 40CrH steel and the heat treatment normalizing process of similar structural alloy steel small size part, the technique includes：The first step, makes material hardness more than or equal to 26HRC by normalizing, occurs pearlite and upper bainite in material structure；Wherein heat the material to the first temperature, critical-temperature Ac3 more than 50 DEG C of first temperature at least above material；Second step, by being tempered the pearlite and upper bainite decomposed in normalized structure, makes material hardness adjust to 20~26HRC, and wherein temperature is second temperature；3rd step, tempering passes through cooling by water after coming out of the stove.The present invention can be realized the control of normalizing hardness to 20~26HRC scopes 40CrH and similar structural alloy steel part, and can eliminate unbalance microstructure, realize intensity, the combination of toughness mechanical performance of material settling out.
Description
Technical field
It is applied to 40CrH steel and similar alloy knot the invention belongs to metal heat treatmet category, more particularly to one kind
The heat treatment normalizing process of structure steel small size part normalizing hardness technical requirements high.
Background technology
40CrH steel and similar structural alloy steel are widely used in the parts such as gear, axle, power transmission shaft, knuckle
Manufacture.Machinery military service when it is as driving member after Surface heat-treatent, the strength character requirement to center portion is higher.
Certain company's turbine shaft material is 40CrH steel, and blank dimension is Φ 24 × 270 (mm), and technical requirements for materials is
Cold drawn rear normalizing, normalizing hardness is 20~26HRC (Rockwell hardness).The Ac3 critical-temperatures of 40CrH
(ferritic transformation is the finishing temperature of austenite during heating) is 788 DEG C, if being heated by normal normalizing process
It is 195~220HB (Brinell hardness) to force the hardness range that air cooling is obtained after to Ac3+30~50 DEG C insulation,
Rockwell hardness or the measurement of actual Rockwell are converted into, its hardness is respectively less than 20HRC, does not meet product design requirement.
According to isothermal normalizing technique, the specific heat capacity of air is 1.3KJ/M3 DEG C, and the coefficient of heat conduction is 0.024W/M
DEG C, about 4290KJ/M3 DEG C of the specific heat capacity of steel, the coefficient of heat conduction is 50W/M DEG C, and both gaps are huge,
100Kg steels are cooled to 650 DEG C from 900 DEG C, 550 DEG C of hot-air about 60~80m3/s are needed
Flow velocity, it is clear that this technological parameter is difficult to control to and realizes in the present state of the art, and is heat-treated at present
Equipment manufacturers can not possibly produce the practical isothermal normalizing equipment of production.So by the direct normalizings of 40CrH
Cannot be operated into 20~26HRC hardness requirement actual productions.
The content of the invention
The technical problem to be solved in the present invention is by 40CrH and similar structural alloy steel small size part
Using the composite heat treating process of heat treatment normalizing, realize normalizing hardness control to 20~26HRC models
The normalizing hardness requirement for enclosing.
The present invention mainly uses following technical scheme：
A kind of heat treatment normalizing process, the technique includes：
The first step, material hardness is made more than or equal to 26HRC by normalizing, occur in material structure pearlite and
Upper bainite；Wherein heat the material to the first temperature, stagnation temperature of first temperature at least above material
50 DEG C of more than Ac3 of degree；
Second step, by being tempered the part pearlite and upper bainite decomposed in normalized structure, makes material hardness
It is adjusted in 20~26HRC, wherein temperature is second temperature；
3rd step, tempering passes through cooling by water after coming out of the stove.
Preferably, forced air cooling is carried out in the first step normalizing.
Further, the forced air cooling is quick cooling, and cool time, material went out cooling in 2 minutes
Surface temperature is less than 200 DEG C afterwards.
Preferably, first temperature range is 900~920 DEG C.
Further, quick cooling is cooled in the 3rd step, cool time is 1 minute, material water outlet
Temperature is 250 DEG C.
The present invention is with the overcooling austenite isothermal transformation kinetics curve of 40CrH steel, and critical-temperature Ac3
=788 DEG C, Ar1=665 DEG C is theoretical foundation, using 900~920 DEG C of heating and thermal insulations of higher temperature.Plus
Hot temperature is improved, and alloying element is more to dissolve in austenite, and austenite composition is further uniform, increased supercooling
The stability of austenite, moves to right C curve, with appropriate air-cooled velocity interpolation Cooling Austenite Transformation.When
During increase forced air cooling speed, material hardness has reached 26~35HRC, and discreteness is big, and goes out in tissue
Upper bainite is showed.Upper bainite has obvious directionality, and hardness is higher.In machining process, because
Its nonhomogeneous hardness with pearlite, forms the difference for being processed performance, so in rear road processing physical dimension essence
The discreteness of degree is very big, causes gear rolling to process accumulated error unqualified.Meanwhile, because of upper bainite and pearlite
Bulk density is different, and phase transition temperature is inconsistent when impewdance matching is heated, and the swollen difference that rises of volume heat, leads during phase transformation
Causing mid-frequency induction hardening crack tendence increases.
For hardness range (i.e. different upper bainite contents) different after normalizing, corresponding different going is formulated
Stress tempering temperature, decomposes uneven phase upper bainite and high density pearlite, hardness is adjusted to 20~
26HRC.Part uses quick water-cooled after tempering is come out of the stove, it is to avoid temper brittleness.
Specific embodiment
A kind of heat treatment normalizing process, the technique includes：
The first step, material hardness is made more than or equal to 26HRC by normalizing, occur in material structure pearlite and
Upper bainite；Wherein heat the material to the first temperature, stagnation temperature of first temperature at least above material
50 DEG C of more than Ac3 of degree；
Second step, by being tempered the part pearlite and upper bainite decomposed in normalized structure, makes material hardness
It is adjusted in 20~26HRC, wherein temperature is second temperature；
3rd step, tempering passes through cooling by water after coming out of the stove.
Forced air cooling is carried out in the first step normalizing.
The forced air cooling is quick cooling, and cool time, material went out surface temperature after cooling in 2 minutes
Less than 200 DEG C.
First temperature range is 900~920 DEG C.
Quick cooling is cooled in 3rd step, cool time is 1 minute, and material leaving water temperature is 250
℃。
Claims (1)
1. a kind of heat treatment normalizing process, the technique includes：The first step, makes material 40CrH hard by normalizing
Degree is more than or equal to 26HRC, occurs pearlite and upper bainite in material structure；Wherein heat the material to
One temperature, 50 DEG C of more than critical-temperature Ac3 of first temperature at least above material 40CrH, first
Temperature range is 900~920 DEG C；Wherein also need quickly to be cooled down in the normalizing of this step, cool time exists
In 2 minutes, surface temperature is less than 200 DEG C after material 40CrH goes out cooling；Second step, is decomposed by being tempered
Part pearlite and upper bainite in normalized structure, make material hardness be adjusted in 20~26HRC, wherein
Temperature is second temperature；Second temperature is chosen according to the hardness after first step normalizing, hardness after normalizing
When scope is 26~30HRC, second temperature scope is 570~590 DEG C；Hardness range is after normalizing
During 31~33HRC, second temperature scope is 590~610 DEG C；Hardness >=34HRC after normalizing, the second temperature
Degree scope is 620~630 DEG C；3rd step, tempering is quickly cooled down after coming out of the stove by water-cooled, and cool time is 1
Minute, material leaving water temperature is 250 DEG C.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510800813.3A CN106755798A (en) | 2015-11-19 | 2015-11-19 | Heat treatment normalizing process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510800813.3A CN106755798A (en) | 2015-11-19 | 2015-11-19 | Heat treatment normalizing process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN106755798A true CN106755798A (en) | 2017-05-31 |
Family
ID=58916288
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201510800813.3A Pending CN106755798A (en) | 2015-11-19 | 2015-11-19 | Heat treatment normalizing process |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN106755798A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108796194A (en) * | 2018-07-06 | 2018-11-13 | 江苏南钢通恒特材科技有限公司 | 42CrMoA rod irons incude normalizing process |
-
2015
- 2015-11-19 CN CN201510800813.3A patent/CN106755798A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108796194A (en) * | 2018-07-06 | 2018-11-13 | 江苏南钢通恒特材科技有限公司 | 42CrMoA rod irons incude normalizing process |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| WD01 | Invention patent application deemed withdrawn after publication |
Application publication date: 20170531 |
|
| WD01 | Invention patent application deemed withdrawn after publication |