GB/T 34891-2017 PDF in English
GB/T 34891-2017 (GB/T34891-2017, GBT 34891-2017, GBT34891-2017)
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Rolling bearings -- Parts made from high-carbon chromium bearing steels -- Specifications for heat treatment
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Standards related to (historical): GB/T 34891-2017
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GB/T 34891-2017: PDF in English (GBT 34891-2017) GB/T 34891-2017
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 21.100.20
J 11
Rolling Bearings - Parts Made from High-carbon
Chromium Bearing Steels - Specifications for Heat
Treatment
ISSUED ON: NOVEMBER 01, 2017
IMPLEMENTED ON: MAY 01, 2018
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Technical Requirements ... 5
4 Test method ... 8
Appendix A (Informative) Effective wall thickness of the ferrule and effective
diameter of the roller ... 16
Appendix B (Normative) Steel ball crushing load test procedure and crushing
load value after heat treatment ... 18
Appendix C (Normative) Decarburization depth of bearing parts after quenching
... 21
Appendix D (Informative) Allowable deformation of bearing ferrule after
quenching and tempering ... 22
Appendix E (Informative) Residual austenite content of bearing part after
quenching and tempering ... 25
Appendix F (Normative) Curved surface hardness correction ... 26
Appendix G (Normative) Pickling inspection procedure ... 28
References ... 31
Rolling Bearings - Parts Made from High-carbon
Chromium Bearing Steels - Specifications for Heat
Treatment
1 Scope
This Standard specifies the technical requirements and test methods for
annealing, quenching and tempering of G8Cr15, GCr15, GCr15SiMn,
GCr15SiMo, GCr18Mo steel rolling bearing rings and rolling elements
(hereinafter referred to as bearing parts) in accordance with GB/T 18254.
This Standard is applicable to the heat treatment quality inspection of the
above-mentioned steel bearing parts process and finished parts, and also to
the heat treatment quality inspection of other high-carbon chromium steel
bearing parts. For bearing parts with special requirements, perform according
to the specifications of corresponding product drawings.
2 Normative references
The following documents are indispensable for the application of this document.
For dated references, only the dated version applies to this document. For
undated references, the latest edition (including all amendments) applies to this
document.
GB/T 230.1-2009, Metallic materials. Rockwell hardness test. Part 1: Test
method (scales A, B, C, D, E, F, G, H, K, N, T)
GB/T 231.1, Metallic materials. Brinell hardness test. Part 1: Test method
GB/T 272-2017, Rolling bearings. Identification code
GB/T 1172, Conversion of hardness and strength for ferrous metal
GB/T 4340.1, Metallic materials. Vickers hardness test. Part 1: Test method
GB/T 6394, Determination of estimating the average grain size of metal
GB/T 17394, Metallic materials - Leeb hardness test
GB/T 24606, Rolling bearings. Non-destructive testing. Magnetic particle
testing
JB/T 7361, Rolling bearings. Test method for hardness of parts
hardness value and size of the tested parts. The test method is
according to provisions of GB/T 230.1, GB/T 231.1, GB/T 4340.1,
GB/T 17394 and JB/T 7361. The hardness value is converted
according to the provisions of GB/T 1172.
b) For steel balls with a nominal diameter not greater than 15.8750
mm and rollers with a nominal diameter not greater than 15 mm,
the measured surface hardness shall be corrected according to the
provisions of Table F.1 and Table F.2 of Appendix F. The hardness
measurement of the spherical roller is performed on the end face
Microstructure
Use a metallographic microscope to test at a magnification of 500 or
1000 times:
a) The spheroidized annealed structure is etched with a 2% nitric acid
solution, and tested according to the size, number and shape of the
carbide particles according to the first level diagram (see Figure 1);
b) The microstructure after quenching and tempering is tested on the
longitudinal section (the steel ball can be inspected on any surface;
in case of controversy, it is subjected to the longitudinal section),
and etched with 2% ~ 4% nitric acid solution;
c) The martensite structure after quenching and tempering is tested
according to the thickness of martensite, the size and quantity of
residual carbide particles according to the second level diagram
(see Figure 2). The microstructure can be inspected under
quenching conditions, and in case of disagreement, it is tested in a
tempered state;
d) The troostite structure after quenching and tempering is tested
according to the shape, size and quantity of troostite according to
the third level diagram (see Figure 3). The acicular or massive
troostite is tested according to the corresponding troostite level
diagram. The acicular and massive mixed troostite is tested
according to the form and type of troostite of the main part in the
field of view;
e) The bainite structure is tested according to the thickness of bainite,
the size and quantity of residual carbide particles according to the
fifth level diagram (see Figure 5).
Reticulated carbide
Use a metallographic microscope to test at a magnification of 500
times. The annealed sample is inspected on the cross section after
normal quenching and tempering; use 4% nitric acid alcohol solution
for deep etch according to the size and degree of sealing of the
carbide net, according to the fourth level diagram (see Figure 4).
Decarburization
depth and surface
soft point
a) Surface decarburization and soft spots can be tested by cold
pickling; the inspection procedures are shown in Appendix G;
b) Decarburization depth is determined in accordance with JB/T 7362.
When it is measured by the metallographic method, use 2% nitric
acid alcohol solution to etch in the annealed state. For the hot steel
Appendix B
(Normative)
Steel ball crushing load test procedure and crushing load value after
heat treatment
B.1 Scope
This appendix specifies the crushing load test procedure and crushing load
value for steel balls whose nominal diameter is ɸ3 mm ~ ɸ50.8 mm.
B.2 Steel ball crushing load test procedure
B.2.1 For each batch of heat-treated steel balls, take three sets of balls (9
pieces) for the ball crushing load test. The dimensional tolerances of the steel
balls shall be the same.
B.2.2 When the semi-finished steel ball after heat treatment is taken for the
crushing test, the surface of the steel ball is not allowed to have surface defects
such as wheel injury, pit, bump or pitting.
B.2.3 When the crushing test is carried out, the loading speed can be loaded
as per 980 N/s ~ 5 880 N/s.
B.2.4 When the steel ball crushing test is carried out, if the load value that is
applied to the steel ball has exceeded the standard, and the steel ball is not
crushed, it can be unloaded; if there is special requirement, the steel ball can
be loaded until it is crushed.
B.2.5 Remove the ball-pressing tire from the test machine; open the safety
cover; quickly remove the steel ball and throw it into the iron box with a cover,
so as to prevent the steel ball from breaking and injuring people; record the test
results.
B.2.6 During the test, if the result is inaccurate due to improper placement of
the steel ball or cracks in the steel ball, the result shall be invalid and the sample
shall be re-tested.
B.2.7 During the test, if the crushing load of the steel ball has reached the
specified standard, and the steel ball is broken during unloading, the result is
treated as qualified.
B.2.8 During the test, the loading speed must not be changed abruptly or
unloaded midway.
Appendix G
(Normative)
Pickling inspection procedure
G.1 Cold pickling
Cold pickling is applicable to the inspection of defects such as soft spots,
decarburization on the surface and cracks on the part surface of the bearing
parts after quenching and tempering. Parts shall be sandblasted and degreased
before pickling, so as to remove surface scale and oil; perform the cold pickling
at room temperature.
G.1.1 Cold pickling procedure
G.1.1.1 Pickling treatment
Place the bearing parts in a 6% ~ 30% (by volume) aqueous solution of nitric
acid pickling tank; the pickling time is about 1 min; then, rinse it in a flowing
cold-water bath for 1 min ~ 2 min.
The concentration of nitric acid (mass fraction: 65% ~ 68%) in the pickling tank
is for reference only; it can be adjusted according to the surface darkness and
size consumption of the parts after pickling. When the surface of the pickling
parts is decarburized, the concentration of nitric acid can be 6%.
G.1.1.2 First clearing treatment
In the first clearing tank, perform clearing treatment for the parts after pickling
for 10 s ~ 20 s; then, rinse it in a flowing cold-water tank for 1 min ~ 2 min. The
distribution ratio of the clearing tank solution can be any one of Table G.1.
Table G.1 -- Distribution ratio of the clearing tank solution
Chemical composition
Category
1 2
Volume ratio
Phosphoric acid a - 10% ~ 15%
Sodium hydroxide 3% ~ 5% -
Potassium permanganate 3% ~ 5% 3% ~ 5%
Trisodium phosphate 6% ~ 9% -
Water Allowance Allowance
Note: When the solution is prepared, add water, then add acid, so as to avoid splashing.
a The mass fraction of phosphoric acid shall be ≥ 85%.
a) qualified surface: the surface is uniform and dark gray;
b) soft surface: the surface is cloud-like dark black spots, and the perimeter
is incomplete;
c) decarburization: the surface is grayish white or dark black spots;
d) crack: the surface is dark black and thin stripe.
G.2 Hot pickling
G.2.1 Hot pickling is applicable to the inspection of surface cracks of bearing
parts after quenching and tempering. Parts shall be sandblasted and degreased
before pickling, so as to remove surface scale and oil.
G.2.2 Before the hot pickling, the bearing parts shall be destressed and
tempered. The tempering temperature shall be greater than 350°C and the
tempering time shall be 2 h ~ 3 h.
G.2.3 Place the bearing parts in 50% hydrochloric acid aqueous solution; heat
the solution to 60°C ± 5°C; the pickling time is 10 min ~ 30 min; then, rinse in
flowing cold water for 1 min ~ 2 min.
G.2.4 Dry the hot-pickled parts and place them under an astigmatism lamp to
visually inspect the cracks.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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