Steel bars and cold-worked steels for corrosion resistance, heat resistance and thermal strength according to GOST 5949-1975 are marked with the following index:
• Marking of steel from 30 to 30Kh2MFA (ИН35 2.2-2.4): the universal mark of steels of the HXG grade is determined by two symbols of the brand, two numerical values corresponding to the chemical composition (in mass fractions) and one letter, indicating the heat treatment of the material.
• Marking of steel 30Kh3MFA (ИН37 2.2-2.4): similar to HXG grade, but with a letter at the end indicating the grade of steel.
• Marking of steel 4130 (ИН15): has two parts, first one is a universal symbol, then slashes and two numbers denoting the chemical composition in percent.
• Marking of steel TU-0-5 (ИН51 2.2-2.4): the mark consists of three symbols of the brand and two numerical values corresponding to the chemical composition (in mass fractions).
• Marking of steel TU- 0-12 and 05Kh9Ni10 (ИН54 2.2-2.4): similar to TU-0-5, with a letter at the end indicating the grade of steel.
• Marking of steel 0-5-5 (ИН55 2.2-2.4): consists of four symbols of the brand and two numerical values corresponding to the chemical composition (in mass fractions).
• Marking of steel 0-8-2 (ИН56 2.2-2.4): consists of five symbols of grade and three numbers corresponding to the chemical composition (in mass fractions).
• Marking of steels from 0-25-1 to 0-40-2 (ИН58 2.2-2.4): the marks consist of three characters denoting the grade of the steel, three numbers corresponding to the chemical composition (in mass fractions) and one letter indicating the heat treatment of the steel.
The chemical composition of steels and cold-worked steels for corrosion resistance, heat resistance and thermal strength according to GOST 5949-1975 are as follows:
• Steel of the HXG grade (30 to 30Kh2MFA): carbon 0.05 to 0.15 %, silicon 0.25 to 0.35 %, manganese 0.60 to 0.90 %, chromium 0.60 to 0.90 %, nickel 0.25 to 0.35 %, molybdenum 0.25 to 0.35 %, phosphorus 0.025 % maximal, sulfur 0.030 % maximal, aluminum 0.010 % maximal, titanium 0.02 to 0.04 %.
• Steel of the 30Kh3MFA grade: carbon 0.05 to 0.15 %, silicon 0.25 to 0.35 %, manganese 0.60 to 0.90 %, chromium 0.60 to 0.90 %, nickel 0.25 to 0.35 %, molybdenum 0.25 to 0.35 %, phosphorus 0.015 % maximal, sulfur 0.030 % maximal, aluminum 0.010 % maximal, titanium 0.02 to 0.04 %, niobium 0.03 to 0.05 %.
• Steel of the 4130 grade: carbon 0.13 to 0.18 %, silicon 0.17 to 0.37 %, manganese 0.50 to 0.70 %, chromium 0.80 to 1.10 %, molybdenum 0.15 to 0.25 %.
• Steel of the TU-0-5 grade: carbon 0.14 to 0.16 %, silicon 0.18 to 0.22 %, manganese 0.30 to 0.40 %, chromium 0.60 to 0.90 %, molybdenum 0.25 to 0.35 %.
• Steels of the TU-0-12 and 05Kh9Ni10 grades: carbon 0.12 to 0.18 %, silicon 0.17 to 0.25 %, manganese 0.30 to 0.40 %, chromium 0.50 to 0.60 %, molybdenum 0.25 to 0.35 %, nickel 0.40 to 0.60 %.
• Steel of the 0-5-5 grade: carbon 0.14 to 0.16 %, silicon 0.18 to 0.22 %, manganese 0.50 to 0.70 %, chromium 0.60 to 0.90 %, molybdenum 0.25 to 0.35 %, phosphorus 0.14 to 0.20 %.
• Steel of the 0-8-2 grade: carbon 0.08 to 0.12 %, silicon 0.16 to 0.22 %, manganese 0.50 to 0.72 %, chromium 0.50 to 0.70 %, molybdenum 0.20 to 0.30 %, phosphorus 0.040 % maximal.
• Steels of the 0-25-1 to 0-40-2 grades: carbon 0.25 to 0.38 %, silicon 0.17 to 0.25 %, manganese 0.30 to 0.40 %, chromium 0.60 to 0.90 %, molybdenum 0.25 to 0.35 %.
The heat treatment of the materials according to GOST 5949-1975 is as follows.
• For the HXG grade (30 to 30Kh2MFA): annealing at temperatures of 700 to 750 oC, depending on the material, then a rapid cooling.
• For the 30Kh3MFA grade: annealing at temperatures of 800 to 850 oC, depending on the material, then an air cooling followed by a tempering at temperatures of 500 to 650 oC.
• For the 4130 grade: an annealing at temperatures of 700 to 750 oC, then a slow cooling, followed by a tempering at temperatures of 500 oC for 1 hour.
• For the TU-0-5 grade: annealing at temperatures of 800 to 850 oC, then an air cooling followed by a tempering at temperatures of 500 to 600 oC.
• For the TU-0-12 and 05Kh9Ni10 grades: an annealing at temperatures of 800 to 850 oC, then an air cooling.
• For the 0-5-5 grade: annealing at temperatures of 900 to 950 oC, then a slow cooling, followed by a tempering at temperatures of 500 oC for 1 hour.
• For the 0-8-2 grade: an annealing at temperatures of 700 to 750 oC, then a slow cooling, followed by a tempering at temperatures of 500 oC for 2 hours.
• For the 0-25-1 to 0-40-2 grades: annealing at temperatures of 700 to 750 oC, then a slow cooling.
By adhering to the requirements of GOST 5949-1975, steels and cold-worked steels for corrosion resistance, heat resistance and thermal strength can be produced and used in different industrial applications. These materials can be easily identified through their marks and chemical compositions. With the help of proper heat treatment, these steels and cold-worked steels can achieve the desired properties in order to satisfy the demands of their applications.
