SU990835A1 - Method for heat treating semiproducts and finished products of martensite-ageing steels - Google Patents

Description

The invention relates to the field of metallurgy, in particular to the heat treatment of semi-finished products and finished products from martensite-aging. steel.

The known method of heat treatment of maraging steel, including heating to Am (60) and cooling l.

The known method of heat treatment of maraging steel, including multiple quenching, with the last quenching performed at a temperature of 20-80 ° C {2j.

However, in this method, the presence of residual austenite is completely eliminated.

The closest in technical essence to the present invention is a method of heat treatment of semi-finished and finished products from martensite aging steels, including cyclic heating to austenization temperature, holding and subsequent cooling to room temperature.

A disadvantage of the known quenching methods is that they cause brittle fracture of the hardened material under conditions of slow loading. .

The aim of the invention is to reduce the tendency to delayed fracture.

The goal is achieved by the fact that, according to the method, heat treatment of semi-finished and finished products from martensite-aging steels, including cyclical heating to austenitization temperature, aging and subsequent cooling to room temperature, heating is carried out to temperature j -f (20-50 C), t . 15 to 20-50 ° C higher than the temperature of the M-7 end of the transformation, and cyclic heating and cooling are carried out to obtain residual austenite in the structure (5-40%).

Thermal treatment consists in the fact that, upon repeated quenching of martensitic steels from a temperature j –f (20–50 ° C) in water or in air, the structure exhibits residual stabilized austenite, the amount of which is proportional to the number of heat treatment cycles. As prose-laboratory tests have shown, the processing is practically the same

It shows the tendency of martensite-aging steels to delayed fracture, since the presence of areas of stabilized austenite in the steel structure is an effective obstacle in the path of fragile fracture. At a jTocT content of less than 5%, high-strength steels are still prone to brittle failure under slow loading, as its amount increases to 15%, the strength properties of the material decrease.

Samples manufactured according to GOST 9651-73 type 1 K (M12) and maraging steel St, OZN17K10V10MT, are subjected to cyclic treatment at 830 ° C (the end temperature of the reverse martensitic transformation according to the dilatometric SheveNar dilatometer is 780-790 ° C ). Mechanical testing of the fPZ-100 tensile testing machine with a deformation rate and P 10-5 s-.

The mechanical properties and the amount of austenite in the steel after such treatment in comparison with the standard are presented in Table. one.

Similar data was obtained for Art. 04H11N9M2D2TYu (Ep832) (IcrS с-) (Table 2).

As can be seen from the data presented, the metal after cyclic processing is characterized by higher values of plasticity when tested for delayed fracture and, therefore, better processability in the process of redistribution and operation. Increasing the heating temperature for quenching above is impractical due to a decrease in the amount of residual austenite during cyclic quenching from a more homogeneous state. Similarly, an increase in the duration of exposure is affected, which, in turn, is also inexpedient.

The expected economic effect is 20,000 rubles.

Table 1

 - 30 MIN-AIR + + 420s - 2 h-air

 - 5 MIN-AIR + + 420 ° С - 2 h-air

830 ° С - 5 min-air-2 cycles + 420С - .2 h-air

830 ° С - 5 min - air 3 cycles + 420 С-2h - air

830 ° С - 5 min-air4 cycles + 420 ° С- 2 h-air

 - 5 min - air - 5 cycles + 420 ° С- 2 h - air

brittle destruction.

.1,297

174 63 11

determined 162

38 58 63 65

determined 160

determined 156

determined 155

determined 143

 - 20 min1 - air - 3 cycles + 420 "С-2 h

 - air + h - 420 s - 2 h

82o C - air -2 cycles + 420 C -2 h

 - air -3 cycles + 2 h

 - 5 min - air + - 2 h

820 С - 5 MIN-AIR + + - 2h

 - 5 min - 2 cycles + - 2 h V - brittle fracture (processed by manual instruction),

Claims (3)

Claim 1. Heat treatment of semi-finished and finished products. from martensitic steels, including cyclical heating to austenitization temperature, exposure and subsequent cooling to room temperature, which is because in order to reduce the tendency to delayed fracture, heating is carried out to Amtg + (20), and cyclical heating and cooling is carried out to obtain residual austenite in the structure (5-40%). .F. A.: Bl and c: .a - ,. one 150 2 9 168 151 29 , 1G29 45 2.0 190 183 8.0 174 13.0 Sources of information taken into account in the examination 1. Perkas MD, Kardonsky V.M. High strength maraging steel. M.I Metallurgists, 1971, p.224. 2. USSR author's certificate 578744, cl. C 21 D 6/00, 1978. 3. Birman S; R. Economically alloyed maraging steel. M., Metallurgists, 1974, p. 145, 155. Compliance with factory technologists.