This drafting unit: The 20th Research Institute of China Electronics Technology Group Corporation This specification assists the drafting unit: Nanjing Hongguang Airborne Equipment Factory The main drafters of this code: Zhang Wenjie, Miao Feng, Zhang Juan, Ma Jing, Gao Hua, Zhang Weiming, Peng Hanmin 1 Scope This specification specifies the requirements, techniques and test methods for the protection of low-alloy structural steel, stainless steel or high corrosion-resistant copper alloy threaded fasteners for outdoor electronic equipment.
This specification applies to the protection of low alloy structural steel, stainless steel and high corrosion resistant copper alloy threaded fasteners.
2 References The following documents contain provisions which, through reference in this specification, constitute provisions of this specification. For any referenced or dated reference document, any subsequent amendments (not including errata content) or revisions do not apply to this specification, but parties using the specification are encouraged to explore the possibility of using the latest version. For undated references, the latest edition applies to this specification.
GB/T3098.17-2000 fasteners mechanical properties hydrogen detection brittle preload test parallel bearing surface method (idtISO15530: 1999) GB/T'1955-1997 metal covering overlay thickness measurement anode dissolution coulomb method GB/T5270- 1985 Metallic coating on metal substrate adhesion test method GB/T6462-1986 Metal and oxide coating cross-section thickness microscopy GB/T11378-89 metal coating thickness profile measurement method GB150.9-86 military equipment environment Test method damp heat test GB.150.10-86 military equipment environmental test method mold test GB150.11-86 military equipment environmental test method salt spray test 3 requirements 3.1 material fastener protection materials should comply with the corresponding material specifications or standards, and Passed the test. Corrosive materials used in the protective treatment process shall be eliminated and neutralized to ensure that corrosion is not caused by the use of these materials, and that the fasteners shall meet the performance requirements specified in this specification after the protective treatment.
195-3.2 plating process selection According to the different metal materials of the fastener base, the corresponding plating process should be selected. The specific requirements are as follows: low-alloy structural steel threaded fasteners should be coated with zinc-chromium coating.
High corrosion-resistant copper alloy threaded fasteners, preferably coated with zinc-nickel alloy plating.
Stainless steel threaded fasteners should be pickled-passivated.
3.3 Plating process 3.3.1 Environmental conditions Work site should be clean, ventilation environment temperature: 1 (TC35C relative humidity: no more than 70% 3.3.2 process 126.96.36.199 zinc chromium coating process zinc chromium coating process as Show: stainless steel pickling, passivation process as shown: before and after the installation of fasteners protective process. 3.3 main process operations 33.3.1 pre-treatment 188.8.131.52.1 unless otherwise specified, all mechanical processing such as: cutting Drilling, heat treatment, etc. shall be completed before the plating of the fasteners. 184.108.40.206.2 According to the type of base metal and the shape and size characteristics of the fasteners, different cleaning processes are used to remove the oil seal, oxide film and metal shavings. And mechanical processing, such as scribing and coloring, should pay attention to avoid excessive corrosion.
220.127.116.11.3 If necessary, remove stress before plating and heat treatment according to the conditions specified in Table 1.
Table 1 Heat treatment for stress relief before plating. Maximum tensile strength Rmax temperature (2) Time (h) No requirement Note 1: Fastening of maximum tensile strength rating greater than 1050Hpa (corresponding to hardness values â€‹â€‹of 34HRC, 340HV, 320) Piece (excluding surface hardening), as required by the ordering party, to relieve stress according to the heat treatment conditions given in the table.
Note 2: It is permissible to use different heat treatment conditions than those in Table 1, such as changing the time and temperature as appropriate, but it must be proved that the change is effective.
Note 3: Due to the need of the ordering party, the surface-hardened fasteners shall be heat treated at 13 (TC15r for a period of not less than 5 h. If the surface hardness of the substrate is allowed to decrease, it may be treated at a higher temperature and for a shorter period of time.
Note 4: Heat treatment should be carried out before all plating preparation or before the aqueous solution cleaning process. The fasteners with excessive oil adhesion should be degreased before heat treatment.
18.104.22.168 Fatigue protection layer According to the type of base metal and the design documents, the fasteners shall be plated according to one of the procedures of 3. 22.214.171.124.2.3. For further detailed plating methods, see Appendix A. 126.96.36.199 Elimination of hydrogen embrittlement If necessary, fasteners can be used to eliminate hydrogen embrittlement according to the heat treatment conditions provided in Table 2.
Table 2 Heat treatment conditions for eliminating hydrogen embrittlement after bond bonding Maximum tensile strength Rmax Temperature (TC) Time (h) No requirement Note l: Heat treatment to eliminate brittle should be in Note 2: For special requirements, allow the temperature to be not higher than tight Firmware: Note 3: Due to the needs of the ordering party, the hardness of the surface ocean surface is allowed to decrease. It can be carried out before the chromate treatment within 4 hours after the end of the search; the heat treatment conditions different from those in Table 2 can be specified by the ordering party. Adopted, but the tempering temperature of the lotus material in the heat.
Fire fasteners, heat treatment should be carried out at 130C1501C, the time is not less than 5h, such as the substrate is produced at a higher temperature and a shorter time.
3.4 Protection of fastener installation process 3.4.1 Application of anti-silver lock agent "When fasteners are required to bear vibration and load requirements, anaerobic locker should be applied to the thread before tightening. Remove excess anaerobic locker.
3.4.2 Coating organic coatings â€œAfter the fasteners are installed, the organic coating should be applied to completely wrap the fasteners.
3.5 plating quality 351 appearance choose different plating process for the corresponding appearance inspection, the specific requirements are as follows: the appearance of the plated zinc-chromium coating is checked according to the method specified in 4.4.1, the basic color is silver gray, and it can be modified. Obtain other colors, such as black, the coating should be continuous and uniform, no leakage coating, bubbles, peeling, cracks, partial over-thickness and inclusions, etc., allowing yellow spots to exist; the appearance of the plated zinc-nickel alloy plating layer is 4. 4.1 The method specified in the inspection, the plating layer should be crystallized, continuous bright, uniform thickness, no peeling, pinholes, bubbles, pitting, etc., allowing partial darkening and discoloration; stainless steel threaded fasteners after pickling-passivation treatment According to the method specified in 4.1, the passivation film should be continuous and dense. After immersing in deionized water, the surface of the fastener should be continuous water film.
3.5.2 Dimensions after plating Unless otherwise specified, measurements shall be made in accordance with the method specified in 4.4.2. The size of the plated fasteners shall be measured in accordance with the method specified in GB/T5267. 3.5.3 Plating thickness 4.3. The fasteners that are not processed after plating (excluding stainless steel fasteners) shall have a main surface thickness not less than the minimum thickness specified by the design. The partial thickness of the edges and edges may be slightly thicker, but shall meet the requirements of GB/T5267. -2002 The thickness requirements specified in Chapter 4 or the design documents. For more details, see the informative Appendix B. 3.5.4 Adhesion strength 4.4 The method specified in the test (excluding stainless steel fasteners). After the test, the plating layer should be continuously attached to the metal substrate, and cracking, peeling or foaming is not allowed.
3.5.5 Hydrogen embrittlement check 4.5 The method specified in the hydrogen brittleness test, if hydrogen embrittlement is found, the process parameters should be modified to ensure protection: Hydrogen embrittlement in the process of the process is eliminated under controlled conditions or according to the heat treatment conditions provided in Table 2 to eliminate hydrogen embrittlement.
3.5.6 Environmental adaptability 188.8.131.52 Damp heat test The test is carried out in accordance with the method specified in 4.4.6. The specimen shall not show rust. Fasteners with a service class of Class 2 are not required to withstand the damp heat performance (see Appendix C for details).
5.6.2 Mold test,) When the electronic equipment is installed by the ordering party, it shall be self-regulated according to the need. 7) When the electronic equipment is installed by the ordering party, it shall be prescribed or not according to the requirements.
Test the method specified in 4.8. The specimen shall not show rust. Fasteners with Class 2 grades are not required to meet the salt spray corrosion resistance requirements (see Appendix C for details on the classification of service grades).
4Quality Assurance Regulations 4.1 Inspection Classification The inspection classifications specified in this specification are as follows: 2 Identification inspection 4.2.1 Inspection items The first batch of coated fasteners shall be subjected to qualification inspection before delivery to the ordering party or when the product specification and process are significantly changed. .
The inspection items are shown in Table 3. The stainless steel fastener inspection items are shown in Table 4. Table 3 Inspection items Table No. Inspection items Identification Inspection Quality Consistency Inspection Requirements Chapter No. Inspection Method Chapter No. Appearance After plating Dimensional plating thickness Attaching strength hydrogen Brittle heat and humidity resistance, mold resistance, salt spray resistance Note: must-check items; items negotiated by OE contractor and ordering party: X is not checked.
Table 4 Stainless Steel Fastener Inspection Item Table No. Inspection Item Appraisal Inspection Quality Consistency Inspection Requirements Chapter No. Inspection Method Chapter No. Appearance After Coating Dimensional Adhesion Strength Hydrogen Embrittle Resistance Moisture Heat Performance Injection Performance Salt Spray Resistance Note: Must Check Project: OE b contractor and the ordering party negotiated the inspection project; X does not check the project.
4.2.2 Qualification criteria The sampling plan for the qualification inspection may be determined by the ordering party and the contractor. According to the inspection method specified in Table 3 (stainless steel fasteners, see Table 4), the fasteners shall be inspected according to the inspection items in the table. When the item is not met, the qualification test is unqualified.
4.3 Quality consistency inspection 4.3.1 Inspection of the appearance of the project, the size of the plating and the thickness of the plating shall be carried out in each production batch. The sampling plan may be determined by the ordering party and the contractor. Stainless steel fasteners are only tested for appearance and post-plating dimensions for each production batch.
4.3.2 Qualification criteria The sampling plan shall be determined by the ordering party and the contractor in consultation, and shall be inspected in the order of the inspection items specified in Table 3 (stainless steel fasteners are shown in Table 4). Anyone who fails to meet the requirements of the requirements of the table shall be deemed to have failed the quality consistency test.
4.4 Inspection method 4.4.1 Appearance Under visual conditions of daylight or natural artificial lighting, visual inspection is used.
4.4.2 The dimensions of 3934-83 after fatigue are measured with a gauge with a tolerance zone of h or H.
4.4.3 The method specified in the fatigue thicknesses of 4955-97, GB6462-86, and GB11378-89 shall be used to measure the plating thickness, or other methods determined by the purchaser and the contractor.
4.4.4 Test method for the adhesion strength specified in 5270-85.
4.4.5 Hydrogen embrittlement test The test method specified in 3098.17-2000 is tested.
4.4.6 Damp heat test Test method specified in 150.9-86, test time 240h. 4.4.7 Test method specified in mold test 150.10-86, test time 28d. 4.4.8 salt spray test 150.11-86 test The method is tested and the sample is subjected to continuous spraying for 48 hours or according to the relevant standards and technical documents, but at least 48h. Appendix A (informative appendix) Supplementary note on the method of fasteners for outdoor electronic equipment fasteners 1 zinc chromium Coating 1.1 Coating Process Zinc-chromium coating (also known as Dacromet) coating process is to apply water-based zinc-chromium coating to the surface of the workpiece by dip coating, brushing or spraying, and baked at 300 Â° C. Bake and cure to form a protective treatment system for inorganic coatings with scaly zinc and chromate as the main ingredients.
1.2 Coating characteristics 1.2.1 It can be used for surface protection of various materials such as steel, cast iron, aluminum and aluminum alloy and iron-based powder. The coating and aluminum and aluminum alloy do not produce galvanic corrosion.
1.2.2 Corrosion resistance is better than electroplating zinc, electroplating chrome, hot dip galvanizing, can be used for fastener protection under higher temperature (not more than 300 Â° C) and more severe corrosion conditions.
1.2.3 Processes will not produce hydrogen embrittlement on the workpiece, which can avoid the danger of hydrogen embrittlement.
1.2.4 Good coating performance for deep-holes, slits, inner wall of pipe fittings, etc. in the workpiece.
1.3 Limitations of application 1.3.1 The curing temperature of zinc-chromium coating is about 300X: It should be considered whether the influence of curing temperature on fastener dimensional accuracy and mechanical properties meets the actual use requirements.
1.3.2 The conductivity of zinc-chromium coating is not good. It is not suitable to use this method to deal with fasteners with conductive connection.
1.3.3 Use zinc-chromium coated protective fasteners with a pitch of not less than 0.3mm. 2 Zinc-nickel alloy plating layer should be used for low alloy structural steel or high corrosion resistant copper alloy threaded fastener with a pitch less than 0.3mm. Alkaline bright zinc (90)-nickel (10) alloy plating process protection, examples are as follows: Table A1 alkaline bright crushing - casting alloy plating conditions and formula examples components and conditions E-sodium hydroxide zinc oxide nickel sulfate sodium tartrate additive Brightener temperature Cathode current density DK anode zinc plate 3 stainless steel pickling-passivation treatment A.3.1 pickling solution formulation and process conditions Table A2 stainless steel pickling solution formulation and process conditions examples components and conditions formula hydrofluoric acid ferric sulfate Time 3.2 Passivation Solution Formulation and Process Conditions Table A3 Stainless Steel Passivation Solution Formulation and Process Conditions Example Component and Condition Formulation Nitric Acid Temperature Time Note 1: After passivation, the acid remaining on the surface should be neutralized in time, thoroughly cleaned, and then Sealing treatment Note 2: Tables A2 and A3 are treated with austenitic stainless steel (eg lCrl8Ni9Ti).
4 Protective measures during fastener installation The ordering party should consider the anti-vibration and load requirements of the fasteners when installing the electronic equipment. Unless there are special requirements, it is generally necessary to take measures to lock the anti-vibration and apply protective coating to further protect the fasteners that are used outdoors, to avoid the failure of the fastener due to vibration and corrosion.
5 Other explanations When applying the fasteners in this specification, the ordering party shall determine the fastener base metal according to the strength requirements of the electronic equipment, the service environment, and whether it bears vibration resistance and load. Material grade 12MnPXt low alloy structural steel, iron brass, lead brass and other high corrosion resistant copper alloy or lCrl8Ni9Ti stainless steel as the base metal material), should be selected to meet the design requirements, and has good environmental corrosion resistance of metal materials.
Appendix B (informative appendix) Keypad thickness selection recommendations corresponding to the service environment Table B1 Excessive thickness corresponding to the service environment Selection Service Environment Grading Marking Applicable Remarks 0.3mm<fastener lay length 0.8nun coated zinc Chromium coating "fastener pitch > 0.8mm for the protection of fasteners with a pitch of <0.8mm galvanized - bismuth alloy for the protection of fasteners > 8mm for the protection of stainless steel fasteners Pickling-passivation treatment Note 1): The plating thickness is limited by the plating process, and is also limited by the size of the fastener. Therefore, within the allowable thickness, the higher the service grade, the thicker the plating thickness. .
2>: The thickness of the zinc-chromium coating provided in the table is based on the density of the coating, but since it is different in specific heat, it is only used as a value for the classification of the coating.
General selection principle of thickness When electrician, the coating composition according to Appendix C (indicative appendix) service environmental condition classification number and corresponding service environmental conditions, example, service environmental condition classification number 4, a very harsh outdoor corrosion condition; service environmental condition classification number 3â€”Outdoor typical temperature conditions; service environment condition classification number 2â€”area where condensation may occur indoors; service environment condition classification number 14 atmosphere and dry room; service environment condition classification number-pure decoration environment.
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