Autocatalytic nickel-phosphorus coating--Specification and test methods
Some standard content:
National Standard of the People's Republic of China
Technical requirements and test methods for autocatalytic nickel-phosphorus coating Autocatalytic nickel-phosphorus coating-Specifications and test methods This standard refers to IS01527-1987 Specifications and test methods for autocatalytic nickel-phosphorus coating. 1 Subject content and scope of application
This standard specifies the requirements and test methods for autocatalytic nickel-phosphorus coating: This standard is applicable to autocatalytic phosphorus coatings on ferrous metal and non-ferrous gold chips substrates. 2 Reference standards
G83505
Surface roughness Terminology Surface and its parameters
GB4956
GB5931
GB5935
GH 6458
GB6459
GB6460
GB6461
GB6462
GB 6463
GB 6465
GB9790
GB 11379
GB12334
GB12335
GB 12609
3 TerminologyWww.bzxZ.net
Measurement of the thickness of non-magnetic coatings on hygroscopic metal substrates Magnetic method GB/T 13913-92
Test method for thickness of gold re-plating and chemical treatment coatings on light industrial productsBeta-ray backscattering methodTest method for porosity of metal coatings on light industrial productsNeutral salt spray test for metal coatings (NSS test)Acetate spray test for metal micro-coatings (ASS test)Copper accelerated acetate spray test for metal coatings (CASS test)Rating of electroplated specimens after corrosion test of metal coatings on substrates with cathodesMicroscopic measurement of thickness of metal and oxide coatingsReview of methods for measuring thickness of metal and other optical coatingsGold Corrosion of metal and other inorganic coverings Night corrosion test (CORR test) Vickers and Knoop microhardness tests on metallic coverings and other related coverings Chromium electroplated coatings for engineering
Definitions and general rules for thickness measurement of metallic and other inorganic coverings Metallic coverings that are anodic to substrate Rating of specimens after corrosion test Current integration Count of metallic coverings and related finishes Sample inspection procedures Important surface refers to certain parts of the workpiece that have been covered or are to be plated, and the coating on this surface is important to the appearance and/or performance of the workpiece.
4 Information that the purchaser should provide to the supplier
4.1 Necessary information
Standard number of this standard;
Thickness of the coating and any base layer, in n
Main surface, should be indicated in detail on the drawing, or with samples with appropriate markings. Parts that do not need to be plated with a self-catalytic nickel-phosphorus chain layer should also be indicated;
GB/T 13913-92
Metallurgical state of the base metal, nominal composition or detailed description. d
4.2 Additional information
If necessary, the purchaser should also provide the following information: Special requirements for pretreatment and limited pretreatment+a
b, special requirements for heat treatment and limited heat treatment1c. In order to minimize the magnetic particles or fine iron contained in the coating, the steel parts shall be demagnetized after bonding. 5 Pretreatment of base metal
5.1 Surface condition
The supplier shall check the visible surface defects on the main surface that may be detrimental to the final finishing, and shall draw the attention of the purchaser to the relevant defects before treatment.
5.2 Stress relief before plating
5.2.1 If the purchaser stipulates that the steel parts shall be stress relieved before plating, unless otherwise specified, the heat treatment conditions listed in Table 1 shall be used. Table 1 Heat treatment conditions for stress relief before plating (except surface quenching parts) Maximum tensile strength value of steel Rr
21050~1 150
=-1 450~1 800
Method: 1) or heat treatment at a higher temperature for a shorter time. Temperature, C
No requirement
190--220
190~22013
190~220
5.2.2 If stress relief is performed after shot peening, the heat treatment temperature should not exceed 220℃. Process
5.2.3 Surface quenched parts should be heat treated at 130-150℃ for not less than 5h. If it is allowed to reduce the hardness of the substrate surface, heat treatment can be performed at a higher temperature for a shorter time. 5.2.4 Non-ferrous metals generally do not require stress relief heat treatment, but brass and copper alloys that are subjected to stress or cause surface cracking in ammonia or ammonium salt solutions should be stress relieved. 5.3 Shot peening
5.3.1 General requirements
If shot peening is specified to produce normal stress, the purchaser shall specify an appropriate method. In order to prevent different stress states on the surface, the entire surface shall be sprayed during the peening process. 5.3-2 Requirements for steel
If shot peening is used to improve fatigue strength, the peening intensity shall be at least:
0. 3 mm for tensile strength less than 1 100 MPa : 0.4mm for steel with tensile strength equal to or greater than 1100MPa. Shot peening should spray all the relevant parts, that is, the steel ball prints overlap each other. In order to avoid deformation, a lower shot peening intensity should be used in thin-walled areas, but this cannot completely and effectively avoid the reduction of thermal strength. 5.3.3 Requirements for non-ferrous metals
The shot peening intensity of non-ferrous metals should be specified by the requirements. 5.4 Base layer
For the following reasons, some base metals need to be bonded with a base layer: a. Increase bonding strength
b. Prevent diffusion:
c. Prevent plating solution contamination.
GB/T13913-92
In order to prevent diffusion and plating solution contamination, a 2-5um thick copper or nickel layer should be electroplated on base metal chips with a content of more than trace amounts of bismuth, cadmium, lead, magnesium, tin and zinc, but bronze and yellow metal are excluded. In order to increase the bonding strength between the coating and certain base metals, a 2 μm copper or copper base layer may be plated on base metals with trace amounts of lead, lead, inlay, saw, titanium and tungsten.
6 Requirements for coatings
6.1 Appearance
The appearance of the main surface in the plated state may be bright, semi-bright or matte. Unless otherwise specified, when visually inspected, the surface should be even and should not have defects such as pitting, cracks, blistering, delamination or nodules. The appearance of the coating depends on the brightness and flatness of the substrate. Defects existing on the base metal before plating, including hidden defects, may reappear on the bonding layer. In addition, post-plating heat treatment may produce spots and discoloration. Such defects may be allowed to exist after consultation and agreement among the relevant parties. 6.2 Surface roughness
If the purchaser specifies the roughness, it should be measured in accordance with the provisions of GB3505. The surface roughness of the coating is generally not better than the surface roughness of the substrate before bonding. 6.3 Thickness
The minimum thickness of the autocatalytic nickel-phosphorus alloy and the bottom layer coated on the main surface and the measurement method shall be specified by the purchaser. The thickness selection is shown in Appendix C.
It should be allowed for the purchaser to specify the sample for measuring the coating thickness at the same time. 6.4 Hardness
If the purchaser requires the hardness value, it shall be measured after heat treatment according to the method specified in GB9790, and the result shall be within ±10% of the hardness value specified by the purchaser (see Appendix B and 8.3). 6.5 Bonding strength
It shall be determined by the purchaser according to the following principles. The coating shall be able to pass one or more bonding strength tests in Article 7.2. a. When the bending test described in Article 7.2, 1 is adopted, the coating shall not fall off. The cracking of the coating on the bending and stretching surface shall not be considered as poor bonding strength of the coating. b. When the thermal shock test described in 7.2.2 is adopted, the bonding layer shall not bubble or peel off. c. When the punching test described in 7.2.3 is adopted, the coating shall not bubble or flake off. d. When the file test described in 7.2.4 is adopted, the coating shall not peel off. 6.6 Porosity
Unless otherwise specified, when the porosity test is carried out by the appropriate method of GB5935, the porosity level is generally not less than 8 when evaluated according to GB6461 and GB12335. In some critical applications, it is required to be completely free of porosity, and the level shall not be less than 10. 6.7 Requirements for its body anti-corrosion performance
: When specified, the autocatalytic nickel-phosphorus alloy plated parts can be tested according to one of the test methods specified in GB6458.G, GB6459, G6460, and GB6465. The test results are evaluated according to GB6461 and GB12335, and the acceptance level is determined by the purchaser. 6.8 Corrosion resistance of coating
If required, the purchaser shall specify the corrosion resistance of the coating and its test and evaluation methods. 6.9 Wear resistance
If required, the wear resistance of the coating and its test and evaluation methods shall be specified. Appendix ID (reference) lists the different test methods currently in use.
6.10 Solderability
GB/T 13913--92
If required, the purchaser shall specify the solderability of the coating and its test and evaluation methods. 6.11 Chemical composition
If required, the purchaser shall specify the chemical composition of the nickel-phosphorus alloy layer. If not specified, the coating shall be provided according to Table 2 and shall comply with the specified range of typical composition. In this case, the chemical composition data is generally not provided. Table 2 Chemical composition of bonding layer
Test method
7.1 Test of coating thickness.
The measurement method used to measure the thickness of the coating at any position on the main surface should ensure that the measurement error is less than 10%. 7.1.1 Weight gain method
7.1.1.1 Principle
The plated sample is the same as the base material of the workpiece. The mass added by the coating is measured and the coating thickness is calculated. 7.1.1.2 Measurement
Measurement of the area of the sample
Weigh the clean and dry sample to an accuracy of 0.001g. Then plate the sample under the process conditions, clean and dry the plated sample, and weigh it to the same temperature as the sample when weighing the plated sample. 7.1.1.3 Calculation
The coating sequence is calculated according to formula (1).
10(m -- )
武a-
Coating thickness.mm;
Sample mass before plating, more:
m.~---Sample mass after plating·B
Density of coating·g/cm\:
Surface area of sample plating.m\.
Note: The density of the chain varies with its phosphorus content. Typical examples are shown in Table 3. Table 3 Density of typical nickel-phosphorus coating
Content, treatment
7.1.2 Cross-section metallographic method
Measure according to the method specified in GB6462. 7.1.3 Engineering tool measurement method
Density+8/cm
Measure the thickness of the specified part on the part or sample before and after plating to calculate the coating thickness. Commonly used measuring instruments such as dry rulers can measure accurately to 0.002 mm at specified locations and obtain a direct reading of thickness. 7.1.4 Magnetic method
GB/T 13913-92
The magnetic method specified in GB4956 is applicable to the thickness measurement of autocatalytic nickel-phosphorus coatings on magnetic substrates with a phosphorus (non-magnetic) content greater than 9% and not subjected to heat treatment. The instrument must be calibrated with steel samples plated in the same solution and the thickness of the coating measured by the microscope method specified in GB 6462.
7.1.58 X-ray backscattering method
Measure according to the method specified in GB5931. The 3-ray backscattering method is limited to base metals with atomic numbers less than 18 or greater than 40. The actual phosphorus content of the coating should be taken into account. Therefore, the measuring instrument needs to be calibrated with a standard sample with the same base and coating phosphorus content as the workpiece being tested.
7.2 Coating bonding strength test
7.2.1 Bend test
The sample is bent 180° along a mandrel with a minimum diameter of 12 mm or 4 times the thickness of the sample and examined with 4 times magnification. 7.2.2 Thermal shock test
For different base metals, according to the requirements of Table 4, the parts coated with white catalytic nickel-phosphorus are heated in a furnace for 1 hour. The workpiece is ignited in room temperature water.
Note: If this test method has an adverse effect on the mechanical properties of the part, this method should not be used and other test piece methods should be used instead. Table 4 Temperature of hot exposure test
Metal valve
Copper and alloy
Aluminum and aluminum alloy
7.2.3 Punching test
30a±10
150±10
250+10
250±10
Use a spring-loaded punch to punch several indentations on the coating, with a distance of about 5mm between each indentation. The punch is processed by cutting, and its head radius is 2mm
7.2.4 File test
If necessary, the plated workpiece can be tested with a file. The file is 45 degrees to the coating to remove the non-main surface so as to expose the interface of the base metal/coating.
7.3 Coating porosity test
The test is carried out in accordance with the method specified in GB5935. 7.4 Determination of coating composition (nickel and phosphorus content) For typical coatings, the alloy composition can be determined by analyzing and determining the nickel and (or) phosphorus content: for non-typical coatings, the alloy composition should be determined by determining the total amount of nickel and phosphorus as specified by the purchaser.
7.4.1 Preparation of samples
Prepare a 20-50μm original nickel-phosphorus bond layer on a lead foil with one side covered to prepare a thin sheet sample for analysis. The aluminum foil can be dissolved and removed with a 10% sodium hydroxide solution. If it is pre-treated with zincate, the coating obtained will have a better bonding strength, but a tightly bonded coating can also be obtained by dipping the clean lead foil into an autocatalytic nickel-phosphorus solution. 7.4.2 Determination of nickel content (dimethylglyoxime gravimetric method) 7.4.2.1 Principle
Dissolve the sample in nitric acid, add citric acid to neutralize the existing iron complex, precipitate the nickel with dimethylglyoxime, then filter, dry and weigh.
7.4.2.2 Reagents
During the analysis, only recognized analytical reagents and distilled water or water of equivalent purity may be used. CB/T 13913-92
(1+1) nitric acid solution, prepared by mixing 1 volume of nitric acid (density about 1.42 g/mL) and 1 volume of water; b. 1% isobutyl ketone or medium alcohol solution: c. Citric acid:
d. (1+1) nitrogen water, density about 0.88 g/mL, diluted with water to 1+1. 7.4.2.3 Equipment
Sand core glass crucible.
Oven, capable of maintaining a temperature of 110±2℃. 7.4.2.4 Procedure
Weigh approximately 0.1 g of the sample (see 7.4.1) to the nearest 0.0001 g and transfer to a 400 mL beaker. Dissolve the sample in 20 mL of nitric acid solution (see a. in 7.4.2.2). Heat the solution to boiling to volatilize the dihydrogen nitrate. Cool the solution to room temperature, dilute it to 150 mL with water, add about 1 g of citric acid (see c. in 7.4.2.2), and then add ammonia water (see d. in 7.4.2.2) to adjust the pH value of the solution to between B and 9. Heat the solution to 60-70°C, and add 30 mL of diacetyl solution (see b. in 7.1.2.2) under stirring. Mix and keep at 60-70°C for 1 hour, then cool to below 20°C, and filter the precipitate with a clean, dry, known-weight sand-core glass plug. Wash the precipitate thoroughly with water, then dry it in an oven, keep it at 110±2°C for 1 hour, cool the precipitate to room temperature in a desiccator, and weigh it accurately to 0.0001%.
7.4.2.5 Expression of results
Nickel content is calculated according to formula (2) and expressed as mass percentage: Ni% = 20.32 (mg-m)
Where: m——mass of sample, 8;
m——mass of carboxylic acid
m2——mass of crucible and precipitate.
7.4.3 Determination of phosphorus content (spectrophotometric method) 7.4.3.1 Principle
Dissolve the sample in nitric acid, oxidize phosphorus with potassium permanganate, and dissolve manganese dioxide precipitate with sodium nitrite. Then react with ammonium molybdate or vanadic acid, and measure the absorbance of the chromium complex at a wavelength of about 420 nm. 7.4.3.2 Reagents
Only recognized analytically pure reagents and distilled water or water of equivalent purity can be used during the analysis. 7.4.3.2.1 Decomposition and nitridation reagents
a. Nitric acid solution, 40% (V/V), prepared by mixing 2 parts by volume of nitric acid (density about 1.42 g/mL) with 3 parts by volume of water. h. Sodium nitrite bath NaNO2 20 g/L.
Potassium permanganate solution KMnO.7.6 g/L
7. 4.3.2.2 Reagents for determination
: Hydrochloric acid solution
Dissolve 20 g of sodium molybdate and 1 g of ammonium vanadate in hot water, mix the two solutions, add 200 mL of nitric acid (density about 1.42 g/ml.) and dilute to 1 000 mL with water, and mix well. b. Phosphorus standard solution, equivalent to 1000 mL. solution containing 100 mg of phosphorus. Weigh 0.439 g of potassium dihydrogen phosphate (KHPO) dissolved in water, transfer this solution into a 1 000 mL volumetric flask with a scale,Dilute with water to the mark and mix well.
This standard solution contains 0.1tng phosphorus in 1mL.
7.4.3.3 Equipment
GB/T 13913---92
Spectrophotometer or photoelectric colorimeter equipped with a filter that reaches the maximum absorbance at a wavelength of about 420nm and equipped with a colorimetric light with a light path of 1mm.
7.4.3.4 Method and Steps
7.4.3.4.1 Preparation of Test Solution
Weigh 0.19~0.21F of the sample (see 7.4.1) to the nearest 0.0001.B+ and transfer it into a beaker and dissolve it with 50mL of nitric acid solution (see a. in 7.4.3.2.1).
Heat slowly until the sample is dissolved, then heat to boiling and remove the brown smoke. Dilute the solution to about 100mL, boil it, and add 25mL of potassium permanganate solution (see c. in 7.4.3.2.1). Boil the solution for 5min.
Add sodium nitrite solution (see b. in 7.4.3.2.1) drop by drop until the manganese dioxide precipitate is dissolved. Boil the solution for 5min. min, then cool to room temperature. Transfer the solution into a 250 mL volumetric flask, dilute to the mark with water, and mix well. 7.4.3.4.2 Blank test
Using the same method and all reagents in the same amount, but without the sample, perform a blank test in parallel with the determination. 7.4.3.4.3 Plotting the standard curve
Take 100 mL of container, add the volume of standard solution shown in Table 5 (see b. in 7.4.3.2.2). Table 5 Preparation of phosphorus standard solution
Volume of phosphorus standard solution, ml.
Note: 1) Haozhunzaibai solution.
The content of each bottle of solution is processed as follows.
The corresponding mass of phosphorus, tng
Add 25mL of molybdate-vanadate solution (see a. in 7.4.3.2.2) Add water to the scale and mix well. Let the solution stand for 5 minutes and inject the solution into the colorimetric blood.
Measure the absorbance at the maximum absorption (about 420 ntn) with a spectrophotometer. Or use a photoelectric colorimeter equipped with an appropriate filter to measure absorbance. In all cases, adjust the instrument's absorbance to Cen with reference to water, and subtract the absorbance of the standard empty solution from the absorbance of the other standard solutions.
Draw a graph, such as using the phosphorus content (mg) of the standard solution as the horizontal axis and the corresponding value of the absorbance as the vertical axis. 7.4.3.4.4 Determination
Pipette 10mL of the test solution and transfer it to a 100mL volumetric flask, add 50mL of water, and then add 25mL of ammonium molybdate-ammonium vanadate solution, add water to the scale and mix thoroughly, and let the solution stand for 5min. Inject this solution into: - a colorimetric tube. According to 7.4.3. 4.3 Method for absorbance measurement. 7.4.3.5 Expression of results
Compare with the standard curve to determine the corresponding phosphorus content. Phosphorus (P) content is expressed as mass fraction and calculated using formula (3). 2.5 (ms-m)
-mass of the sample, mgt
武f: m-
GB/T 13913-92
基础s-phosphorus content of the aliquot of the test solution used for determination, mgm\-phosphorus content of the aliquot of the blank test solution, n1g. 7.4.4 Determination of phosphorus content (titration method)
7.4.4.1 Principle
Prepare the test solution as specified in 7.4.3.4.1, treat it with ammonium platinum bath to form ammonium phosphate, and then treat it with potassium nitrate solution to convert it into triammonium phosphate: add sodium hydroxide solution, and titrate the unreacted sodium hydroxide with standard hydrochloric acid solution. 7.4.4.2 Reagents
During the analysis, it is recommended to use recognized analytical reagents and distilled water or water of equivalent purity. Reagents for dissolution and oxidation (see 7.4.3.2.1), b. Ammonium molybdate reagent.
Dissolve 15g ammonium molybdate in 80mL of water, add 6ml ammonia water (density about 0.88g/mL), dilute to 1U00mL and mix well,
Dissolve 21g ammonium citric acid in 60mL of water, add 33mL nitric acid (density about 1.42g/mL), dilute to 100mL, mix well:
Mix equal volumes of solution A and solution B while stirring, let the solution stand for 12h, and filter if necessary. c. Nitric acid solution KNO, "TUR/L.
d. Sodium hydroxide standard solution c.Mix equal volumes of solution A and solution B, let the solution stand for 12 hours, and filter if necessary. c. Nitric acid standard solution KNO, "TUR/L.
d. Sodium hydroxide standard solution c.Mix equal volumes of solution A and solution B, let the solution stand for 12 hours, and filter if necessary. c. Nitric acid standard solution KNO, "TUR/L.
d. Sodium hydroxide standard solution c.800～1 1001
Note: 1) Micro cracks may occur in the coating with this hardness range. 8.4 Heat treatment to improve bonding strength
Heat treatment requirements
No requirements
Heat treatment according to Appendix R
Heat treatment in Appendix B
In order to improve the bonding strength of the autocatalytic nickel-phosphorus coating on certain base metals, heat treatment should be carried out according to the requirements of the purchaser, or the workpiece with a bond thickness of 50x or less than 50um should be heat treated according to the recommended specifications in Table 8. Thicker coatings should be heat treated for a longer time. The heat treatment temperature recommended in Table 8 has no effect on the alloy base. Table 8 Heat treatment conditions to improve bonding strength
Aged alloys
Age-hardened lead and aluminum alloys
Age-hardened lead and aluminum alloys
Magnesium and aluminum alloys
Copper and copper alloys
Nickel and tin alloys
Titanium and titanium alloys
Carbon steel and alloy steels
Molybdenum alloys
Time, h
Temperature, C
130=15
160±10
100+10
190+10
230+10
280+10
210+10
200-10
9.1 Unless the purchaser and the supplier agree to adopt other representative sampling plans, sampling should be carried out in accordance with the relevant provisions of GB12609. 9.2 When the sampling plan requires separate plated samples, these samples should be plated along with the parts. Note: The autocatalytic plating-phosphorus process is affected by the rapid change of solution concentration. It is recommended to sample and check the coating every day. For the mirror layer that contains a certain phosphorus content and must be subjected to corrosion testing, frequency sampling should be considered. All samples used in the sampling plan should be prepared with the base material of the workpiece sample plated according to this specification. 9.3 Unless agreed by the supplier, all specimens shall be provided by the supplier. GB/T 13913 92
Appendix A
Static load test method for determining brittleness
(reference)
A1 Four specimens of parts shall be randomly selected from each inspection batch. Four specimens coated with autocatalytic nickel-phosphorus alone may also represent each inspection batch.
A2 The load (N) or the bending and elongation (mm) of the parts used in the test shall be specified and consistent with the following requirements. The specimen parts such as spring pins or lock rings installed in holes or on rods shall be the same as the parts used. The maximum continuous tensile stress shall be applied to the specimen. Unless otherwise specified, the specimen shall be kept at 20±1°C for at least 200h under the rated load and then checked for cracks. b. For test specimen parts such as pressure vessels, fasteners, and springs, where static tensile loads in service exceed 25% of the minimum tensile strength specified for the base material, the test shall be subjected to a sustained load equal to 75% of the minimum tensile strength specified for the base material. Testing is not required unless special fixtures or limit load devices are available to meet the service requirements for these parts when the static tensile loads in service exceed 50% of the rated minimum tensile strength of the base material. For parts where static tensile loads in service are between 25% and 50% of the minimum tensile strength specified for the base material, special fixtures and limit load devices are available to meet the service requirements, and four specially prepared test specimens may represent each batch of parts. The dimensions of the cylindrical test specimen are as specified in Figure A1. A 60° V-groove is machined approximately at the center of the standard length of the specimen, with the cross-sectional area at the root of the V-groove being approximately equal to half the total cross-sectional area of the reduced cross-sectional area of the specimen. The radius of curvature at the bottom of the V-groove should be 0.25 ± 0.13 mm. The axis (load direction) of the slotted cylindrical specimen should be perpendicular to the oriented short fiber structure.
A3 The specimen has the same chemical composition (alloy) as the part it represents and reaches the same hardness after heat treatment. When the test group represents the part, the entire coating process including all pre-plating and post-plating treatments should be carried out simultaneously with the production part. Unless otherwise specified, the part or specimen should be subjected to the specified load for at least 200 h at 20 ± 1 ° C. Then check for cracks. 4
A1 Specimens for the static load test method for determining hydrogen embrittlement Appendix
Heat treatment to increase hardness
(reference)
B1 The hardness values obtained according to temperature, heat treatment time and alloy composition are listed in Tables B1 and B2. The hardness value curves after heat treatment at different temperatures and times are shown in Figures B1 and R2. These curves are correct only when the phosphorus content is 5% to 10%. At temperatures above 350°C and above 500°C, the errors of alloys outside this composition range are more significant. In addition, below 400°C, longer heat treatments of more than 1 h often produce the desired effect. Therefore, Figure B2 shows that heat treatment at 400°C for 1 h or 285°C for 12 h will achieve the highest hardness. B2 Rapid heating and rapid cooling should be avoided during heat treatment. When determining the heat treatment time, the mass of the workpiece (kg) should be considered. It is best to heat treat in a cyclic or reducing atmosphere. However, steel parts with a tensile strength exceeding 1400MPa cannot be heat treated in a hydrogen atmosphere. It should be noted that high-temperature heat treatment may have an adverse effect on the mechanical properties and corrosion resistance of some base materials. In order to obtain the required final hardness value, the best combination of heat treatment time and temperature should be considered. Table B1400C Effect of holding time on hardness during heat treatment Content
Instantaneous
Table B2400C Effect of holding time on hardness during heat treatment above Temperature
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