GOST 28426-90

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  ГОСТ 28426-90

GOST 28426−90 Thermodiffusion strengthening and protection of metal products. General requirements for technological process

GOST 28426−90

Group B04

INTERSTATE STANDARD

THERMODIFFUSION STRENGTHENING AND PROTECTION OF METAL PRODUCTS

General requirements for technological process

Thermodiffusion strengthening and protection of metal products.
General requirements for technological process

ISS 25.200
AXTU 0070

Date of introduction 1991−01−01

INFORMATION DATA

1. DEVELOPED by the Ministry of public education of the BSSR, USSR State Committee on management of quality and standards

2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on management of quality and standards from 16.01.90 N 44

3. INTRODUCED FOR THE FIRST TIME

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

The designation of the reference document referenced	Item number
GOST 3.1121−84	1.8
GOST 3.1405−86	1.8
GOST 9.301−86	2.1
GOST 12.0.003−74	7.2
GOST 12.0.004−90	7.13
GOST 12.1.005−88	7.6
GOST 12.1.014−84	7.8
GOST 12.1.041−83	7.5
GOST 12.2.003−91	7.9
GOST 12.2.007.9−93	7.9
GOST 12.2.032−78	7.11
GOST 12.2.033−78	7.11
GOST 12.3.002−75	7.3
GOST 12.3.004−75	7.3, 7.13
GOST 12.3.005−75	7.13
GOST 12.3.009−76	7.10
GOST 12.3.020−80	7.10
GOST 12.4.004−74	7.12
GOST 12.4.011−89	7.12
GOST 12.4.021−75	7.7
GOST 12.4.045−87	7.12
GOST 12.4.068−79	7.12
GOST 12.4.103−83	7.12
GOST 2789−73	1.6
GOST 2912−79	Annex 2
GOST 2999−75	6.5
GOST 3773−72	Annex 2
GOST 4526−75	Annex 2
GOST 6912.2−93	Annex 2
GOST 9450−76	6.5
GOST 9849−86	Annex 2
GOST 20495−75	1.9
GOST 30558−98	Annex 2
GOST 30559−98	Annex 2
THAT 6−09−5304−86	Annex 2
THAT 6−12−94−78	Annex 2
SNiP 2.04.05−86	7.4
SNiP 2.09.02−85*	7.4
_________________ * Instead of acting 31−03−01 SNiP, here and hereafter. — Note the CODE.
ONTP 24−86	7.4

5. REPRINTING. November 2005


This standard applies to the technological process of thermodiffusion strengthening and protection of metal products in the synthesized powder saturating environments.

The standard is designed for enterprises and organizations using thermal diffusion method of hardening metal products in powder environments.

1. GENERAL PROVISIONS

1.1. Thermodiffusion strengthening in the synthesized powder environments — one of the methods of chemical-thermal treatment of metal products.

The method consists in heating metal articles Packed in a container together with the powder mixture to a predetermined temperature, and aging at this temperature until obtaining the desired thickness of the diffusion layer. The contents of the container to prevent oxidation of the fusible sealing stopper or protective atmosphere.

When the thermal diffusion treatment is carried out, the saturation of the surface metal products by one or several elements (metals and non-metals in various combinations). The formation of the diffusion layer occurs as a result of direct contact of the surface of the product with particles of the powder mixture, and formed in the container during heating and aging of the active gas phase.

1.2. The composition of the saturating environment must ensure that the diffusion layer the optimal composition and structure defining surface hardening and protection products, in relation to the conditions of their intended use.

1.3. Thermal diffusion processing in the synthesized powder environments applicable to metal articles made of alloys based on iron, Nickel, cobalt, refractory metals, aluminum, copper, sintered metal materials, etc., of any geometrical shape and size.

1.4. Thermal diffusion processing in the synthesized powder environments leads to changes in the chemical, and in some cases, the phase composition of surface layers of products and is carried out to impart desired mechanical and physical-chemical properties of wear resistance, Rashoroshina, resistance to chemical and electrochemical corrosion and erosion, cavitation etc.

1.5. The thermal diffusion treatment of the product subjected to pre-heat (annealing, normalization, improvement) and machining.

1.6. Thermal diffusion processing in the synthesized powder environments ensures the preservation of the surface roughness, the arithmetical mean deviation of the profile which is not lower than 0.63 mm according to GOST 2789.

1.7. After the thermal diffusion treatment, if necessary, can be made of the operation of finishing machining: grinding, polishing, etc.

1.8. The contents and layout of technical documents for the process of thermal diffusion processing must comply with GOST 3.1121. Requirements for completing the documents according to GOST 3.1405.

1.9. Basic terms and definitions GOST 20495. Additional terms and explanations given in Appendix 1.

2. REQUIREMENTS TO THE PROCESSED PRODUCTS

2.1. Products coming on the thermal diffusion treatment, must meet the requirements of the drawing, to be dry, clean, free of traces of oil, coolant, paint, rust, scale and mechanical damage in accordance with GOST 9.301.

2.2. Protection areas on the surface from diffusion saturation is carried out by coating them with protective coatings, electrolytic coatings and other measures, taking into account the used process of thermal diffusion processing.

2.3. Heat treatment after diffusion saturation is prescribed for products required by the operating conditions make the core of a certain complex of physical-mechanical properties. Heat treatment after diffusion saturation is allowed to put products, the performance of which is provided only the surface layer or level of physical and mechanical properties of the core of the product is achieved by the selected mode of cooling and temperature of diffusion saturation.

2.4. The heat treatment is selected in accordance with the chemical composition of the material and the requirements to the mechanical properties of the core.

2.5. Mode is selected and the method of heating during heat treatment must guarantee the integrity (no cracking and spallation) and the obtaining (or maintaining) the desired structure, chemical and phase composition and the thickness of the diffusion layer.

3. REQUIREMENTS FOR TECHNOLOGICAL MATERIALS

3.1. For the preparation of synthesized saturating environment and conducting thermal diffusion treatment materials to be applied and substances produced according to the current normative-technical documentation.

3.2. Components of powder mixtures from which the synthesized saturating environment, must have a certificate indicating the marks and names of the substance, designation of the standard or technical conditions on which they are made.

3.3. The composition of the synthesized powder mixture should include: substances that are sources of saturating elements; a stabilizing additive; reducing agents (in the case of oxides as sources of the saturating elements); technological fillers (refractory metal oxides), protecting the mixture from sintering and (or) absorbing excess heat in the fusion reactions; activators of the synthesis of (halogen-containing substances).

To store the synthesized powder mixture should be in closed containers with proper marking.

3.4. If you reuse the synthesized powder mixture to it shall be added to the activator in the amount of 1% to 3% of the mass of the used compound and from 20% to 50% fresh mix.

3.5. Quality control of the synthesized saturating environment is conducted by the control regime of thermal diffusion processing samples of the metal workpiece.

Temperature and time parameters of the control regime, the shape, size of samples and types of control are determined by the requirements of processed product and are installed by the developer documentation.

3.6. Control of the composition of the synthesized saturated environment is allowed to carry out chemical, x-ray, electron-graphical and other analysis methods.

3.7. The technological process of thermal diffusion saturation of the surface layer of metal products synthesized powder mixtures needs to create a diffusion layer based on compounds of boron (Borisovna), chromium (chromium plating), etc.

Appendix 2 shows the composition of the initial components of the synthesized powder mixture for formation of a saturating environment when the thermal diffusion treatment of steel products based on single-phase boriding and chromium.

4. REQUIREMENTS FOR TECHNOLOGICAL PROCESS

4.1. The technological process of thermal diffusion processing of products consists of:

1) load product into the container and fill them the synthesized powder mixture;

2) conducting a thermal diffusion process;

3) unloading and cleaning products;

4) control on appearance, thickness and microhardness;

5) heat treatment products (if necessary);

6) quality control.

4.2. The process of thermal diffusion treatment of metallic products must be conducted under conditions precluding oxidation.

4.3. During thermal diffusion processing with the use of containers with fusible shutter loading of goods and filling their synthesized powder mixture should meet the following requirements:

1) the distance between the bottom of the container and product must be not less than 20 mm;

2) the powder in the container should be evenly compacted;

3) the distance between products or product and the container walls must be at least 10 mm;

4) packing of goods into a container should avoid the plastic deformation in process of saturation;

5) saturating the layer of powder on the product should be not less than 30 mm.

In one container is allowed to handle single or multiple (batch) of products.

In the container, if necessary, can be control samples or specimens.

4.4. Saturation without a container to hold bulky products by installing them on pallets and filling with the working surface of the saturating powder mixture. The process of thermal diffusion processing must be carried out in a protective atmosphere.

4.5. Load the containers and a tray in the oven should be not later than 24 h after packaging.

4.6. The temperature-time mode of the process of thermal diffusion saturation choose by mean of the processed products (material grade, shape, dimensions) and the required parameters of the diffusion layer (thickness, chemical and phase composition, structure, hardness).

The duration of exposure is calculated since the heating of the container to the saturation temperature. Warm-up to the saturation temperature depends on the size of the container, the composition of the saturating mixture, the mass of packaging, temperature and capacity of the furnace and other parameters.

4.7. Cooling after saturation must comply with the requirements of the workpiece, and to eliminate the possibility of oxidation products and saturating the mixture.

4.8. To unpack containers after cooling them to room temperature. The contents of the container discharged into a special tray or other device, excluding the possibility of contact with the saturating mixture of foreign substances.

4.9. Products should be cleaned from the powder mixture and, if necessary, rinsed in hot and cold water and to preserve.

4.10. To clarify the temperature-time parameters of technological process of thermal diffusion processing of products in powder synthesized environments should be conducted the control treatment experienced the product samples with subsequent analysis of parametric dependencies, time, temperature, thickness and chemical composition of the diffusion layer.

Annex 3 shows the characteristics of the process of thermal diffusion processing of steel products for single phase in the synthesized powder boronovanii environment.

Annex 4 shows the characteristics of the process of thermal diffusion processing of steel products in chrome plating powder in the synthetic environment.

5. REQUIREMENTS FOR TOOLING AND EQUIPMENT

5.1. The thermal diffusion treatment of the metal products may be performed in furnaces of various designs of periodic and continuous action: mine, chamber and pusher-type furnace with nichrome, silicon carbide and other heaters.

Depending on the specific conditions and volumes of production of heating furnace and the device must be equipped with teplonositelya.

The heating device must provide:

1) heating the product to a predetermined temperature;

2) the uniformity of the temperature field within ±10 °C;

3) the automatic registration, regulation and record temperature with an accuracy of ±10 °C.

5.2. The size and shape of the container for thermal diffusion processing is selected in accordance with the dimensions and shape of the workpieces with the requirements set out in clause 4.3.

Containers shall be made of heat-resistant steels or alloys with a wall thickness of not less than 5 mm. In containers welded seams must be double (inside and outside of the container). In the case of the thermal diffusion processes at temperatures below 800 °C allowed the production of containers made of low alloy or carbon steels.

5.3. Pallets for thermodiffusion processing of large products need to be a minimum thickness of 10 mm.

Pallets should be made of low alloy or carbon steels.

6. REQUIREMENTS FOR QUALITY CONTROL

6.1. The quality of diffusion layer control on the products or check the samples passed the thermal diffusion treatment along with products.

Depending on the process of thermal diffusion processing and the function of the product control of the diffusion layer:

1) appearance;

2) total thickness of the diffusion layer;

3) the thickness of the outer zone of the diffusion layer;

4) the microstructure of the diffusion layer;

5) the phase and chemical composition of the diffusion layer;

6) hardness of the surface layer.

6.2. The product must have a uniform matte gray, silver or shiny color of the surface.

6.3. The thickness and microstructure of diffusion layer control on ProTrainer the microsection metallographic method.

6.4. Phase and chemical composition of the diffusion layer was controlled by x-ray diffraction or electron microprobe methods.

6.5. The hardness of the surface layer is determined according to GOST 2999 or GOST 9450.

7. REQUIREMENTS OF SAFETY AND ECOLOGY

7.1. In aerial environment and waste waters in the presence of other substances or factors, the processes of thermal diffusion processing and protection of metal products synthesized in saturated environments, toxic substances do not form and do not require special measures for the protection of the environment.

Shall be disposal of waste products by secondary use in the process in accordance with claim 3.4. The remaining amount of the powder mixture should be used as a technology of the fillers according to claim 3.3 or in other mixtures.

7.2. When carrying out a thermodiffusion treatment processes should be provided for measures to protect workers from possible effects of hazardous and harmful factors in accordance with GOST 12.0.003:

high gas content and dust in the working area;

high surface temperature of equipment and tooling.

7.3. In the development and implementation of the process of thermal diffusion processing should be taken into consideration General requirements for industrial processes according to GOST 12.3.002, and General requirements for processes of thermal treatment of metals according to GOST 12.3.004 (in terms of sec. 2).

7.4. The thermal diffusion treatment is carried out in premises that meet the requirements ONTP 24−86 and SNiP 2.09.02.

Plots of thermal diffusion processing must be equipped with forced ventilation in accordance with SNiP 2.04.05 with cleaning and dispersion in the atmosphere of the exhaust air.

7.5. Maximum allowable concentration of powder substances in the premises and ventilation suction systems must not exceed the limits established by GOST 12.1.041.

7.6. The air of working zone shall conform to the requirements of GOST 12.1.005.

7.7. Local exhaust ventilation device shall be made in accordance with the requirements of GOST 12.4.021.

7.8. The condition of the air environment is controlled according to GOST 12.1.014 and techniques approved by the Ministry of health of the USSR.

7.9. The equipment used for the thermal diffusion treatment, must meet the requirements of GOST 12.2.003 (in terms of sec. 5) and GOST 12.2.007.9.

7.10. Handling and transportation on the site of thermal diffusion processing must comply with the requirements of GOST 12.3.009 and GOST 12.3.020.

7.11. Working place thermodiffusion treatment ergonometrically must comply with the requirements of GOST and GOST 12.2.032 12.2.033.

7.12. When you work in the area of thermal diffusion processing, it is necessary to use means of individual protection in accordance with GOST 12.4.011:

1) special clothing according to GOST 12.4.045;

2) protection of hands according to GOST 12.4.103;

3) protection of the skin of the hands from exposure to dust, toxic media (dermatological protective equipment according to GOST 12.4.068);

4) the means of respiratory protection (filter respirators according to GOST 12.4.004 and dust respirators of a type I-2K).

7.13. Requirements to professional selection of staff to work in the area of thermal diffusion processing must comply with GOST 12.3.004 (in terms of sec. 7) host 12.3.005. Training and knowledge of the employees — according to GOST 12.0.004.

7.14. In areas of thermal diffusion processing should be developed and used instructions on safety, taking into account individual peculiarities of production.

ANNEX 1 (reference). THE TERMS USED IN THE STANDARD AND THEIR EXPLANATIONS

ANNEX 1
Reference

The term	Explanation
The thermal diffusion treatment	Heating of products in reactive saturating mixture and aging at a predetermined temperature with the purpose of changing the chemical composition, structure and properties of the surface layer
Synthesized saturated environment	Powder, chemically active medium, the obtained solid phase physico-chemical interaction of initial components when heated to a certain temperature. Note. Physico-chemical interaction sources of saturated elements, activators and reducing agents is carried out by synthesis using a synthesized air environment, metallothermic recovery, homogenizing annealing, etc.

ANNEX 2 (informative). THE COMPOSITION OF THE SYNTHESIZED POWDER MIXTURE ON THE SOURCE COMPONENTS

ANNEX 2
Reference

1. Thermal diffusion Borisovna

Source components	Mass content, %	Standard or the
Boric anhydride (About)	15−20	TU-6−12−94
Aluminium (Al)	10−12	The corresponding NTD
Iron (Fe)	26−30	GOST 9849
Aluminium oxide (AlO)	35−44	6912.2 GOST, GOST 30558, GOST 30559
Torobert potassium (KBF)	3−5	THAT 6−09−5304−86

2. Thermodiffusion chromium

Source components	Mass content, %	Standard or the
Chromium oxide (CrO)	38−52	GOST 2912
Aluminium (Al)	12−18	The corresponding NTD
Aluminium oxide (AlO)	32,5−36,5	6912.2 GOST, GOST 30558, GOST 30559
Magnesium oxide (MgO)	2−3	GOST 4526
Torobert potassium (KBF)	0,5−1,5	THAT 6−09−5304−86
Ammonium chloride	1−3	GOST 3773

APPENDIX 3 (reference). THE TEMPERATURE-TIME CHARACTERISTICS OF THE THERMAL DIFFUSION TREATMENT OF STEEL FOR SINGLE-PHASE BORONOVANII

APPENDIX 3
Reference

Mode		The layer thickness for steel, µm
Temperature, °C	Time, h	U8A, U10A, U8	9KHS, 60S2, 5KHNM	CVH, KH12MF, X12M	3Х2В8, 4H5MFS
850	2	20−30	20−30	14−16	16−18
4	35−40	40−50	18−20	18−20
6	45−50	50−65	26−28	24−26
12	55−60	60−70	35−40	30−35
900	2	40−50	50−60	18−20	20−22
4	50−60	60−70	21−23	22−24
6	65−75	75−85	30−32	30−32
12	80−85	85−90	35−40	35−40
950	2	65−75	70−75	40−41	40−46
4	70−80	75−85	46−50	48−52
6	90−100	110−120	60−64	60−65
12	105−110	115−125	67−70	65−70

The boride layer hardness HV 0.1 1100−1600

ANNEX 4 (reference). THE TEMPERATURE-TIME CHARACTERISTICS OF THE THERMAL DIFFUSION TREATMENT OF STEEL IN CHROME PLATING

ANNEX 4
Reference

Mode		The layer thickness for steel, µm
Temperature, °C	Time, h	45	U8A, U8, U10A	X12M, KH12F1, 4H5MFS	5KH3V3MFS (DI-23)
1000	4	10−12	7−9	7−9	10−12
6	13−15	10−12	10−12	12−14
8	15−17	14−16	12−14	16−18
1050	4	14−16	17−19	12−14	17−19
6	17−19	20−22	17−19	20−23
8	20−22	23−25	20−22	25−27
1100	4	17−19	20−22	12−14	20−22
6	20−22	23−25	25−30	30−32
8	20−22	25−27	36−38	36−38

The hardness of the carbide layer 1600−2000 HV 0.1

The text of the document is verified by:
the official publication of the
M.: STANDARTINFORM, 2005