GOST 10495-80 Hexagon Nuts for Flanged Connections for Pn above 10 to 100 MPa

INTERSTATE STANDARD

Hexagon Nuts for Flanged Connections for Pn above 10 to 100 MPa (above 100 to 1000 kgf/cm²). Specifications	GOST 10495-80

Effective date 01.01.82

This standard applies to hexagon nuts for flanged connections of valves, fittings and pipelines used in the chemical and petrochemical industries at Pn above 10 to 100 MPa (above 100 to 1000 kgf/cm²), at temperatures from minus 50 to plus 510 °C.

The requirements of Section 1, except for the “Weight, kg” parameter, Sections 2–4, and clauses 5.1, 5.2, 5.4, 5.6 are mandatory; the other requirements of this standard are recommended.

(Revised edition, Amendment No. 2).

1. DESIGN AND DIMENSIONS

1.1. The design and dimensions of nuts shall conform to those shown in Figure 1 and Table 1.

Fig. 1

Table 1

Nominal thread diameter d	Width across flats S		Collar diameter D	Height H h14	Circumscribed circle diameter D₁		Permissible offset of the hole axis relative to the flats, max	Collar height h H14	Weight, kg
	nom.	tolerance			nom.	tolerance
12	19	-0.28	18.0	12	21.9	-0.8	0.35	2.0	0.019
14	22		20.9	14	25.4	-0.9			0.031
16	24		22.8	16	27.7				0.039
20	30		28.5	20	34.6	-1.0		3.0	0.077
22	32	-0.34	30.4	22	36.9	-1.1	0.40		0.093
24	36		34.2	24	41.6	-1.3			0.133
27	41		39.0	27	47.3				0.194
30	46		43.7	30	53.1	-1.4			0.277
33	50		47.5	33	57.7	-1.5	0.50	4.0	0.389
36	55	-0.40	52.3	36	63.5	-1.7			0.446
39	60		57.0	39	69.3				0.637
42	65		61.8	42	75.0	-1.8		5.0	0.777
45	70		66.5	45	80.8				1.100
48	75		71.3	48	86.5	-1.9			1.197
52	80		76.0	52	92.3		0.60		1.420
56	85	-0.87	80.8	56	98.0	-1.2			1.688

Example of a nut designation with thread diameter d=36 mm, made of steel grade 35Kh, without coating:

Nut M36. 35Kh GOST 10495-80

The same, with coating 02, 6 μm thick:

Nut M36. 35×026 GOST 10495-80

(Revised edition, Amendment No. 1).

2. Technical requirements

2.1. Nuts shall be manufactured in accordance with the requirements of this standard, to working drawings approved in accordance with the established procedure.

2.2. Nuts shall be manufactured from bar stock and forgings.

2.3. Steel grades and their application parameters shall conform to those specified in Table 2.

Table 2

Steel grade	Standard designation	Limiting application parameters
		temperature, °C	nominal pressure, MPa (kgf/cm²)
30Kh	GOST 4543	From minus 50 to plus 200	≈ 63(630)
35Kh		From minus 50 to plus 400	≈ 80(800)
38KhA
40Kh
30KhMA		From minus 50 to plus 510	≈ 100(1000)
35KhM
25Kh1MF	GOST 20072

Note. By agreement between the customer and the manufacturer, it is permitted to use other steel grades approved by Gosgortekhnadzor, provided their mechanical properties are not lower than those specified in Table 3.

2.4. Blanks for nuts shall be heat-treated — quenched and tempered. Heat treatment regimes are given in the Appendix.

2.5. The mechanical properties of blanks at a temperature of 20 °C in the heat-treated condition shall conform to those specified in Table 3.

Table 3

Steel grade	Yield strength, MPa (kgf/mm²)	Tensile strength, MPa (kgf/mm²)	Elongation, %	Impact strength, J/cm² (kgf×m/cm²)	Hardness HB
	min
30Kh	392 (40)	618 (63)	17	588 (6)	187 … 229
35Kh, 38KhA, 40Kh	490 (50)	657 (67)	16		212 … 248
30KhMA, 35KhM, 25Kh1MF

(Revised edition, Amendment No. 1).

2.6. The acceptance characteristics are tensile strength, yield strength, elongation and impact strength.

2.7. Coarse-pitch metric thread — per GOST 24705, with tolerance class 6H per GOST 16093.

2.8. The deviation from perpendicularity of the nut bearing surface (angle in Fig. 2) relative to the thread axis shall not exceed 30°.

2.9. The permissible slope of the flats (angle in Fig. 2) and their non-parallelism shall not exceed 30°.

Fig. 2.

2.10. Machined surfaces of nuts shall have no cracks or tears.

2.11. The thread shall be clean and free of burrs, tears, or threads with torn or incomplete profile. Dents on the thread that prevent the go gauge from screwing in are not permitted.

2.12. Nuts used at temperatures up to 200 °C shall, at the customer’s request, be manufactured with a coating. The type of coating shall be per GOST 9.303. The coating thickness shall be per GOST 9.306. The coating designation shall be per GOST 1759.0.

2.13. Protective coatings shall be uniform; blisters and peeling are not permitted.

2.14. Surface roughness requirements for coating shall be per GOST 9.301.

3. ACCEPTANCE RULES

3.1. Acceptance rules shall be per GOST 17769.

3.2. Each nut shall be checked for compliance with the requirements of clauses 1.1, 2.7–2.14, 5.1, 5.2.

3.3. Nuts shall be submitted for acceptance in batches. A batch shall consist of nuts of a single designation, manufactured from a single batch of blanks.

3.4. Verification of nuts for compliance with the requirements of clause 2.5 shall be carried out based on the test results of each batch of blanks.

3.5. A batch of blanks shall consist of metal from a single melt and a single heat-treatment charge.

3.6. Hardness testing of blanks shall be performed at 100%. For blanks 500 mm long and longer, hardness shall be measured at both ends and along the length at intervals of no more than 500 mm.

3.7. One percent of the batch of blanks, but not less than 2 pieces, having the lowest and highest hardness values in the given batch, shall be tested for compliance with the requirements of clause 2.5.

It is permitted to select blanks for mechanical testing with intermediate hardness values. In this case, hardness is an acceptance characteristic.

3.8. The number of specimens tested from each inspected blank shall be: one for tensile testing and two for impact testing.

3.9. If unsatisfactory mechanical property test results are obtained for at least one specimen, retesting shall be performed on double the number of specimens from the same blanks or other blanks of the same batch with the same hardness, only for the type of test that gave the unsatisfactory result.

3.10. A batch shall be considered acceptable if the retest results are positive.

If unsatisfactory test results are obtained, the batch of blanks may be resubmitted for acceptance after testing blanks with the next hardness level.

3.11. Blanks with hardness that does not ensure the required mechanical properties specified in Table 3 may be accepted for delivery after repeated heat treatment with the corresponding tests performed.

The number of repeated heat treatments shall not exceed two. Additional tempering is not considered a repeated heat treatment.

4. TEST METHODS

4.1. Visual inspection (clauses 2.10, 2.11, 5.1, 5.2) shall be performed without the use of magnifying devices.

4.2. Nut dimensions (clauses 1.1, 2.7–2.9) shall be checked using limit gauges, templates, and universal measuring instruments.

4.3. Hardness determination (clause 2.5) — according to GOST 9012.

4.4. Tensile testing (clause 2.5) — according to GOST 1497.

4.5. Impact toughness testing (clause 2.5) — according to GOST 9454, specimen type 1.

4.6. Sampling method — according to GOST 7564.

4.7. Methods for checking the quality and thickness of the coating (clauses 2.12–2.14) — according to GOST 9.302. Coating thickness is checked on the end faces or flats of the nut.

5. MARKING, PACKAGING, TRANSPORTATION AND STORAGE

5.1. Marking of nuts, depending on the steel grade, shall conform to that specified in Table 4.

5.2. Nuts shall be marked, in the locations specified in Table 4, with the following information:

• lot number;
• trademark of the manufacturer.

5.3. Height of marking characters:

• 2.5 mm — for nuts with d 27 mm;
• 4 mm — for nuts with d 27 mm.

5.4. Marking characters shall be clearly visible to the naked eye.

5.5. Marking shall be performed by the stamping method.

5.6. A lot of nuts shall be accompanied by a quality passport certifying their compliance with the requirements of this standard.

The quality passport shall contain the following data:

• name of the manufacturer;
• designation of the nuts;
• number of nuts;
• lot number;
• steel grade;
• test results (with the date indicated);
• designation of this standard;
• type and thickness of coating (for coated nuts);
• stamp of the quality control department.

5.7. (Deleted, Amendment No. 1).

5.8. Requirements for packaging, transportation, storage and marking of containers — according to GOST 18160.

5.9. When stored indoors, nuts shall be kept in containers.

5.10. By agreement between the customer and the manufacturer, coated nuts may be exempted from preservation treatment.

Table 4

Steel grade	Marking location
30Kh
35Kh, 38KhA, 40Kh
30KhMA, 35KhM, 25Kh1MF

Note. The marking shall be retained when the steel is replaced with an equivalent grade.

Appendix

Recommended

Heat treatment conditions for blanks

Steel grade	Quenching		Tempering
	heating temperature, °C	cooling medium	heating temperature, °C	cooling medium
30Kh	850-870	Oil	580-620	Water and oil
35Kh	850-870		560-600
38KhA	850-870		560-600
40Kh	850-870		560-600
30KhMA	850-880		580-620
35KhM	850-880		590-630
25Kh1MF	930-960		680-720

INFORMATIONAL DATA

1. DEVELOPED AND SUBMITTED BY the Ministry of Chemical and Petroleum Machine Building of the USSR

DEVELOPERS

E.Ya. Neiman; L.F. Berezin (project leader)

2. APPROVED AND PUT INTO EFFECT by Decree of the USSR State Committee for Standards dated 30.12.80 No. 6073

3. SUPERSEDES GOST 10495-74

4. REFERENCE REGULATORY AND TECHNICAL DOCUMENTS

Designation of the referenced regulatory document	Clause number
GOST 9.301-86	2.14
GOST 9.302-88	4.7
GOST 9.303-84	2.12
GOST 9.306-85	2.12
GOST 1497-93	4.4
GOST 4543-71	2.3
GOST 7564-97	4.6
GOST 9012-59	4.3
GOST 9454-78	4.5
GOST 16093-81	2.7
GOST 17769-83	3.1
GOST 18160-72	5.8
GOST 20072-74	2.3
GOST 24705-81	2.7

5. Reviewed in 1990. The validity period restriction was lifted by Decree of Gosstandart dated 25.02.91 No. 159

6. REISSUE (December 1998) with Amendments No. 1, 2, approved in July 1986, February 1991 (IUS 11-86, 5-91)