Some standard content:
Ministry of Machinery and Electronics Industry of the People's Republic of China Standard SJ3197-89
Heat treatment of beryllium bronze elastic elements
Published on February 10, 1989
Implemented on March 1, 1989
The Ministry of Machinery and Electronics Industry of the People's Republic of China issued the Ministry of Machinery and Electronics Industry of the People's Republic of China Standard Heat treatment of beryllium back copper elastic elements
1 Subject content and applicable scope
1.1 Subject content
SJ3197-89
This standard specifies the relevant rules for material acceptance, heat treatment process specifications, heat treatment quality control and inspection of corrugated bronze elastic elements for the electronics industry.
1.2 Scope of application
This standard applies to the heat treatment of corrugated paste steel bars and strip elastic elements for the electronics industry, and is only for reference for rod and wire elastic elements.
2 Reference standards
GB5233
GB3134
GB4340
GB6397
JB1821
Processing bronze—Chemical composition and product shape Beryllium copper bars and strips
Beryllium bronze wire
Bronze rod
Chemical composition analysis method of beryllium bronze
Vickers hardness test method
Metal tensile test method
Metal tensile test specimen
Elastic properties test method of metal strip
3 Terminology of heat treatment of beryllium paste copper
3.1 Annealing
Annealing of beryllium bronze means heating and keeping warm for a sufficient period of time below the β phase eutectoid transformation temperature. The purpose of annealing is mainly to soften the structure and eliminate stress.
3.1.1 Low temperature annealing
Generally at 550~570℃, keep warm for 2~6h. The cold-processed beryllium bronze undergoes recrystallization through low temperature annealing to eliminate work hardening, which is usually used as an intermediate softening process. 3.1.2 Stress relief annealing, generally at 150~200℃, keep warm for 1~1.5h, also known as stabilization treatment. 3.2 Solution treatment
Solution treatment of beryllium bronze is also called annealing, which is heated above the solvus line, kept warm for a certain time, and then quickly cooled by water. The solution temperature is generally 770~790℃. Approved by the Ministry of Machinery and Electronics Industry of the People's Republic of China on February 10, 1989 and implemented on March 1, 1989
SJ3197-89
The purpose of solution treatment is to fully dissolve the beryllium-rich phase (β phase) in beryllium bronze into the matrix to obtain a supersaturated α solid solution, so as to prepare the organization for subsequent aging strengthening; at the same time, the material after solution treatment has good plasticity and is easy to process and shape in the factory.
3.3 Aging||tt ||Solution treated or solution treated and then cold worked beryllium bronze is kept at an appropriate temperature for a certain period of time to decompose the supersaturated α solid solution and precipitate the strengthening phase.
The purpose of aging treatment is mainly to precipitate the strengthening phase through the supersaturated α solid solution, obtain the ideal high strength, hardness, elasticity and other properties, and obtain stable part size and shape. 3.3.1 Peak aging: Beryllium blue steel containing 1.6~2.0% beryllium is kept at 320~340℃ for 2~3 h aging treatment, due to the full precipitation of the strengthening phase, its strength and hardness reach the highest value. Bee value aging is suitable for elastic components with high comprehensive performance requirements.
3.3.2 Under-aging: lower than the peak aging temperature, generally 250~280℃, keep warm for 2~3h. Due to insufficient precipitation of the strengthening phase, the highest strength and hardness are not reached. Under-aging is suitable for elastic components with low requirements for strength and elasticity, but certain requirements for plasticity, toughness and fatigue performance; or it is used to improve the cutting performance of beryllium bronze. 3.3.3 Over-aging: higher than the peak aging temperature, generally 350~400C, keep warm for 0.5~2h. Due to the aggregation of strengthening phases, the strength and hardness are significantly reduced. Over-aging is suitable for elastic components with low requirements for strength and elasticity, but high working temperature, and high requirements for organizational stability and conductivity. 3.3.4 Step-by-step aging: first carry out low-temperature pre-aging at 150~240℃, and then carry out pre-aging at 320~340℃. Peak aging. Step aging can improve elastic limit, fatigue life and stress relaxation resistance. 3.3.5 Double or multiple aging: Aging is completed twice or multiple times. It can reduce deformation, stabilize size and further improve mechanical properties.
4 Beryllium bronze material
4.1 Brand, variety, supply status and mechanical properties The brand, variety, supply status and mechanical properties of beryllium bronze materials shall comply with the provisions of Table 1. 4.2 Chemical composition||tt| |The chemical composition of beryllium back copper material shall conform to the provisions of Table 2, 2
QBeMg2-0.1
QBcMg1.7-0.1
Plate, strip
Plate, strip
Plate, strip
Plate, strip
Plate, strip
SJ319789
Grade, variety,
State and mechanical properties
Tensile strength
39 0 ~ 590 | | tt | | 370 ~ 570 | | tt | | 540 ~ 785 | | tt | | 390 ~ 590 | | tt |
590~690
690~830
Elongation
Vickers hardness
90~130
120~180
180~215
215~250
90~130
120~180
180~215
215~250bZxz.net
Note: For strips and ribs with a thickness of <0.25mm and wires with a diameter of <1.0mm, 0g and 3 are not specified. Remarks
GB3134
QBeMg2-0.1
QBcMg1.7--0.1
1.90~2.20
1.35~2.10
1.60~1.85
1.30~2.00
1.60~1.7 9
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Table 2Chemical composition
Alloy element
0.20~0.40
0.20~0.40
0.20~0.50
Note: ①Impurities not listed in the table are included in the total impurities, home
0.10~0.25
0.10~0.25
②Chemical composition analysis method is based on YB600 regulations and agreement between supply and demand parties. 4.3 Quality
Impurity elements (maximum)
0.150.15/0.15
0.150.15/0
0.150.15/0
0.05~0.15
010015015
0.05~0.15
0.0050.50
0.100.15/0.15
4.3.1 The size, allowable deviation and surface quality of the supplied materials shall comply with the requirements of YB552, GB3134 and YB720.
The grain size and β phase structure of beryllium copper bars and strips shall conform to the requirements of Table 3. Table 3 Refractory grain size and B phase structure
0.30~1.50
Average grain size
0.015~0.045
0.015~0.055
0.015~0.060
5 Heat treatment equipment
Heating equipment
A small amount of granular form is allowed (primary and secondary), but long strips or continuous chains are not allowed (third level).
The main heating equipment for bronze plating heat treatment includes: box-type electric furnace, tubular protective gas electric furnace, well-type air circulation electric furnace vacuum electric furnace, salt bath tank and oil bath tank, etc.: It is recommended to use special equipment for beryllium bronze heat treatment: ammonia decomposition protective atmosphere solid bath furnace and vacuum aging furnace
5.2 Temperature control instrument
The automatic temperature controller recording instrument, thermocouple, compensation wire, etc. used in the heating furnace should be calibrated regularly: To ensure the control accuracy, it is recommended to use PID or microcomputer automatic temperature controller. Generally, the heating should be effectively uniform in the overflow area, and the uniformity should be guaranteed within 5 t
5.3. Cooling trough
The cooling trough should be located below or near the solid solution furnace, and have sufficient volume and provide clean running water to ensure rapid and uniform cooling of the parts
6 Heat treatment of beryllium bronze
6.1 Heat treatment process specifications
SJ3197-89
Conventional treatment (solid solution and peak aging) process specifications shall comply with the provisions of Table 4 Table 4
QBcMg2-0.1
QBeMgl.7-0.1
QBcMg2-0.1
QBeMgl.7-0.1
Degree (℃)
780±10
Temperature change (C)
320±5
340±5
Conventional heat treatment process specifications
Component thickness or diameter (mm)
@3~020
Note: ① The aging treatment referred to in this section is the peak value aging treatment. ②The specifications in the thickness and diameter column refer to the 5 specifications in the table for each grade, and the state in the material state column refers to the 4 states in the table for each grade. When the parts are large or the furnace is full, the solidification and aging holding time should be appropriately extended, holding time (min) holding time (h) 6.1.2 In order to obtain special properties such as high ductility, electrical conductivity, dimensional accuracy, fatigue life, low elastic aftereffect and stress relaxation resistance, a special aging heat treatment process can be used, and its mechanical properties are not limited by Table 5. 6.2 The mechanical properties after aging treatment shall comply with the provisions of Table 3. 5 QBeMg2-0.1 QBwMg1.7-0.1 Note: ①S is the aging state.
SJ3197-89
Mechanical properties after aging treatment
Tensile strength
11001340
1180~1410
1240~1480
1270~1520
1030~1240
11001310
1180~1380
1230~1450| |tt||Elongation
Hardness
325~400
350430
360440
380~450
310370
330410
345~420
360430
②The requirements for the microstructure and performance of beryllium bronze after heat treatment in this section are applicable to bars and strips, and are only for reference to rods and wires. 6.3 Heat treatment quality control
6.3.1 Heat treatment surface quality control
Before heat treatment, clean the parts with cleaning agents such as gasoline and anhydrous ethanol, dry them, and remove surface oil, hand sweat, water stains or other corrosive substances.
The solution treatment of beryllium bronze should be carried out in a protective atmosphere or vacuum heating furnace. If the aging treatment of beryllium bronze is carried out in air, oil bath or salt bath medium, it will cause surface oxidation and discoloration. Although it has no significant effect on the mechanical properties of the material, it will affect the appearance and is not conducive to welding and electroplating. In order to prevent oxidation and improve the surface finish, it is recommended to use protective atmosphere or vacuum aging heat treatment. After aging, it should be cooled to below 100℃ before stopping the vacuum or stopping the protective atmosphere. Commonly used protective gases are: nitrogen, hydrogen, carbon monoxide, which are generally obtained by decomposition of ammonia, petroleum gas, methanol, ethanol, etc. The gas purity and flow rate should be strictly controlled during operation. When vacuum aging is used, the general vacuum degree should be kept above 6.67P (5×10-mmHg). 6.3.2 Control of grain growth during solution treatment The quality of solution treatment directly affects the performance of beryllium bronze after aging. Therefore, the grain growth during solution treatment must be strictly controlled according to the grain size requirements in Table 3. Preliminary tests should be carried out for important parts, and the appropriate solution treatment process specifications should be determined according to the grain size requirements. If the solution treatment temperature is too low or the time is too short, insufficient solid solution will be caused, reducing the aging strengthening effect; and the grains are too fine6
SJ3197--89
small, resulting in an increase in the amount of grain boundary reaction during aging and a decrease in performance. If the solution treatment temperature is too high or the time is too long, it will cause overheating and grain coarsening, mechanical properties will decrease, and even cause local overburning and quenching cracking. If the solution treatment temperature exceeds 800℃, overheating will occur, and if it exceeds 850C, it will cause overburning.
6.3.3 Cooling after solution treatment
After solution treatment, the parts should be quenched into water from the furnace as soon as possible to prevent the precipitation of the second phase. The fire delay time should not exceed 2S for thin and fine parts, and 3S for general parts. The cooling medium for the fire is flowing water, and the water temperature should be below 25℃.
6.3.4 Re-quenching
When the grain size is too fine or the β phase is too much after solution treatment, and the mechanical properties do not meet the requirements (except for the grain size exceeding the upper limit), solution treatment is allowed to be repeated. Generally, the number of re-quenching shall not exceed 2 times. 6.3.5 Control of discontinuous precipitation of grain boundaries during aging treatment For materials with grades QBe2, QBe1.9, and QBe1.7, the discontinuous precipitation of r phase at the grain boundary is sensitive to the aging temperature. The aging temperature and time should be strictly controlled. After peak aging, the grain boundary reaction amount should be controlled within 8%. For QBeMg2-0.1 and QBeMg1.7-0.1 materials containing trace magnesium, the aging temperature or time can be appropriately increased because the addition of magnesium significantly inhibits the grain boundary reaction; after peak aging, the grain boundary reaction amount shall not exceed 2%. 6.3.6 Control of aging deformation
During the aging process of beryllium bronze materials, the length and volume shrink due to changes in the organizational structure. For parts with complex shapes, deformation occurs due to uneven shrinkage. To prevent or reduce deformation, a reasonable fixture can be used; if necessary, manual correction can also be used, and then stress relief annealing is performed. 7 Inspection of beryllium copper paste elastic elements after heat treatment After heat treatment, beryllium bronze elastic elements should be inspected for appearance and various organizational and performance inspections in accordance with the relevant product technical conditions, design documents and process documents. 7.1 Appearance inspection
7.1.1 After heat treatment, the surface of the parts shall not have blistering, cracks, oxidation and rust. 7.1.2. After aging treatment, the geometric dimensions of the parts shall meet the requirements of the drawings. If there are special technical requirements, they should be inspected on special equipment.
7.2 Metallographic inspection
7.2.1 The metallographic specimen should be taken from the largest longitudinal section perpendicular to the surface and parallel to the direction of the material. The evaluation standards for the grain size, β phase and grain boundary reaction are shown in Appendix A, Appendix B and Appendix C. 7.2.2 After solution treatment, the grain size and β phase structure of the material shall comply with the provisions of Table 3. 7.2.3 After aging treatment, in the metallographic structure of the material, a fine, dispersed phase structure shall be formed in the α matrix, and the grain boundary reaction amount shall comply with the provisions of Article 6.3.5. 7.3 Hardness test
7.3.1 The hardness test shall be carried out in accordance with GB4340. The test load should be selected according to Table 6. 7
Test load
State (c)
Allowable thickness (mm)
SJ3197-89
Table 6 Vickers hardness test load table
Degree (cr)
Allowable thickness (mm）
0.15~0.25
0.25~0.35
0.35~0.50
0.50~0.90
Note: ①The hardness value must be a direct measurement value and the conversion value shall not be used. ②Microhardness tester is allowed The microhardness of the measuring plate (Hm) is 200g at this time. 7.3.2 After solution treatment, the hardness value shall comply with the provisions of soft materials in Table 1. 7.3.3 After aging treatment, the hardness value shall comply with the provisions of Table 5. 7.4 Tensile test
Aging state (s)
Allowable friction (mm)
0.15~0.25
0.30~0.45
0.45~0.70
7.4.1 The tensile test is carried out according to GB228, and the sample is prepared along the rolling direction. The strips and bands use the P01 or P8 samples of GB6397. If it is impossible to directly sample from the parts, a standard sample should be specially made and heat treated with the parts in the same furnace.
2 After aging treatment, the tensile strength and elongation of beryllium bronze materials of different grades and states shall comply with the requirements of Table 57.4.2
.
7.5 Elastic performance test
For important elastic components, it is recommended to conduct elastic performance test to detect the bending elastic limit, elastic modulus and elastic aftereffect of the material after aging treatment. The elastic performance test shall be carried out in accordance with JB1821. Magnification
Average grain diameter (μm)
Magnification
Average grain diameter (um)
SJ3197--89
Appendix A
Standard figure for evaluation of beryllium copper solid solution grain size
(reference)
Magnification
Average grain diameter (um)
Magnification
Average grain diameter ( μum)
Magnification
Average diameter of grains (um)
Magnification
Average diameter of grains (um)
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Magnification
Average diameter of grains (um)
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Appendix B
Beryllium paste copper β phase structure rating standard diagram
(reference)
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