Proceedings of the Tomsk Polytechnic Institute named after S. M. Kirov, Order of the October Revolution and Order of the Red Banner of Labor

Volume 241
1975

Recommended Friction-Welding Parameters for End Tools Made of Tungsten-Molybdenum Steel R6M5 with Structural Steel 45 on the MOD MF-327 Semiautomatic Machine

Yu. A. Yevtyushkin, V. I. Yegorov, A. V. Repin

(Presented by the scientific seminar of the Department of Equipment and Technology of Welding Production)

In the tool industry, tungsten-molybdenum steels, in particular the new steel grade R6M5, are finding ever wider application for the manufacture of cutting tools. The composition of steel R6M5 (average) is: 0.85% C, 5% Mo, 6% W, 4% Cr, 2% V.

The structure of the steel in the as-supplied condition is fine-grained (sorbitic) pearlite and excess carbides. Hardness after annealing: HB 207–235.

The mechanical properties of the steel in the hardened condition are as follows: HRC 63.5; \(G_{\mathrm{izg}} = 315\text{--}330\ \mathrm{kg/mm^2}\) [1].

Tungsten-molybdenum steel R6M5 differs from tungsten steel R18 (for which the welding technology has been developed) in chemical composition and in thermophysical properties, primarily in thermal conductivity. Therefore, it became necessary to develop friction-welding parameters for end tools made of tungsten-molybdenum steel R6M5 with structural steel 45. The parameters were developed on a MOD MF-327 semiautomatic friction-welding machine designed by the Frezer plant. The spindle speed was 1500 rpm. The friction-welding parameters were selected experimentally. The following parameters of the friction-welding modes were varied in turn: \(P_{\mathrm{n}}, P_{\mathrm{p}}, t_{\mathrm{n}}\), where

\(P_{\mathrm{n}}\) — pressure during heating, \(\mathrm{kg/cm^2}\);

\(P_{\mathrm{p}}\) — pressure during forging, \(\mathrm{kg/cm^2}\);

\(t_{\mathrm{n}}\) — time during heating, s.

After welding, the blanks were placed in an electric muffle furnace heated to 500–650°C. The blanks were then annealed in shaft-type annealing furnaces according to the procedures of the Tomsk Tool Plant. Heating to a temperature of 840–860°C and holding at this temperature for 2–3 hours were followed by slow cooling in the furnace to 500–550°C. After this, cooling was carried out in a thermos to 200°C, followed by further cooling in air. From annealing, the blanks were sent to the turning section. The welding flash was removed and specimens were made for torsion testing. Based on the results of torsion testing and study of the fracture character, the ranges of recommended welding parameters for blanks made of steel R6M5 with structural steel 45 were constructed, and recommended friction-welding parameters for the new steel grade R6M5 were selected.

To study the friction-welding technology of blanks made of steel R6M5 with structural steel 45, the following were taken:

For a diameter of 11 mm, the following groups of conditions were used:

Group I — \(P_{\mathrm{h}} = 1\ \mathrm{kg/cm^2}\); \(P_{\mathrm{p}} = 2.5\ \mathrm{kg/cm^2}\); \(t_{\mathrm{p}} = 2\ \mathrm{s}\),
\(t_{\mathrm{h}}\) was varied from 5 to 10 s in 1-s increments,

Group II — \(P_{\mathrm{h}} = 1.5\ \mathrm{kg/cm^2}\); \(P_{\mathrm{p}} = 3\ \mathrm{kg/cm^2}\); \(t_{\mathrm{p}} = 2\ \mathrm{s}\),
\(t_{\mathrm{h}}\) was varied from 3 to 8 s in 1-s increments,

Group III — \(P_{\mathrm{h}} = 2.0\ \mathrm{kg/cm^2}\); \(P_{\mathrm{p}} = 3.5\ \mathrm{kg/cm^2}\); \(t_{\mathrm{p}} = 2\ \mathrm{s}\),
\(t_{\mathrm{h}}\) was varied from 2 to 5 s in 1-s increments.

For a diameter of 20 mm, the following groups of conditions were used:

Group I — \(P_{\mathrm{h}} = 2.5\ \mathrm{kg/cm^2}\); \(P_{\mathrm{p}} = 4.0\ \mathrm{kg/cm^2}\); \(t_{\mathrm{p}} = 2\ \mathrm{s}\),
\(t_{\mathrm{h}}\) was varied from 10 to 15 s in 1-s increments.

Group II — \(P_{\mathrm{h}} = 3.2\ \mathrm{kg/cm^2}\); \(P_{\mathrm{p}} = 5.0\ \mathrm{kg/cm^2}\); \(t_{\mathrm{p}} = 2\ \mathrm{s}\),
\(t_{\mathrm{h}}\) was varied from 7 to 12 s in 1-s increments.

Group III — \(P_{\mathrm{h}} = 4.0\ \mathrm{kg/cm^2}\); \(P_{\mathrm{p}} = 5.5\ \mathrm{kg/cm^2}\); \(t_{\mathrm{p}} = 2\ \mathrm{s}\),
\(t_{\mathrm{h}}\) was varied from 6 to 10 s in 1-s increments.

For a diameter of 22 mm, the following groups of conditions were used:

Group I — \(P_{\mathrm{h}} = 2.5\ \mathrm{kg/cm^2}\); \(P_{\mathrm{p}} = 4.7\ \mathrm{kg/cm^2}\); \(t_{\mathrm{p}} = 2\ \mathrm{s}\),
\(t_{\mathrm{h}}\) was varied from 12 to 18 s in 1-s increments.

Group II — \(P_{\mathrm{h}} = 3.3\ \mathrm{kg/cm^2}\); \(P_{\mathrm{p}} = 4.7\ \mathrm{kg/cm^2}\); \(t_{\mathrm{p}} = 2\ \mathrm{s}\),
\(t_{\mathrm{h}} = 12;\ 16\ \mathrm{s}\).

Group III — \(P_{\mathrm{h}} = 4.0\ \mathrm{kg/cm^2}\); \(P_{\mathrm{p}} = 5.2\ \mathrm{kg/cm^2}\); \(t_{\mathrm{p}} = 2\ \mathrm{s}\),
\(t_{\mathrm{h}}\) was varied from 9 to 16 s in 1-s increments.

For each condition, the welding allowance was measured. On the basis of the data obtained for the welding allowances, graphs were plotted showing the change in the welding allowance of blanks made of R6M5 steel with structural steel 45 as a function of \(t_{\mathrm{h}}\), \(P_{\mathrm{h}}\), and \(P_{\mathrm{p}}\): for diameter 11 mm (Fig. 1); for diameter 20 mm (Fig. 2); for diameter 22 mm (Fig. 3).

Fig. 1. Graphs of the change in welding allowance of blanks Ø11 mm made of R6M5 steel with steel 45 as a function of \(t_{\mathrm{h}}\), \(P_{\mathrm{h}}\), and \(P_{\mathrm{p}}\).

Fig. 2. Graphs of the change in welding allowance of blanks Ø20 mm made of R6M5 steel with steel 45 as a function of \(t_{\mathrm{h}}\), \(P_{\mathrm{h}}\), and \(P_{\mathrm{p}}\).

The torsion-test results for the blanks showed that the strength of the weld seam under all conditions was satisfactory and ranged from 35 to 43 \(\mathrm{kg/mm^2}\) (the permissible torsional strength limit for welded tool blanks is 35 \(\mathrm{kg/mm^2}\) [2]). The exceptions were 4 conditions:

\[ P_{\mathrm{h}} = 1\ \mathrm{kg/cm^2};\quad P_{\mathrm{p}} = 2.5\ \mathrm{kg/cm^2};\quad t_{\mathrm{h}} = 5\ \mathrm{s},\quad t_{\mathrm{p}} = 2\ \mathrm{s}. \]

\[ P_{\mathrm{h}} = 1\ \mathrm{kg/cm^2};\quad P_{\mathrm{p}} = 2.5\ \mathrm{kg/cm^2};\quad t_{\mathrm{h}} = 6\ \mathrm{s},\quad t_{\mathrm{p}} = 2\ \mathrm{s}. \]

\[ P_{\mathrm{h}} = 2.5\ \mathrm{kg/cm^2};\quad P_{\mathrm{p}} = 4.0\ \mathrm{kg/cm^2};\quad t_{\mathrm{h}} = 10\ \mathrm{s};\quad t_{\mathrm{p}} = 2\ \mathrm{s}. \]

\[ P_{\mathrm{h}} = 3.2\ \mathrm{kg/cm^2};\quad P_{\mathrm{p}} = 5.0\ \mathrm{kg/cm^2};\quad t_{\mathrm{h}} = 7\ \mathrm{s};\quad t_{\mathrm{p}} = 2\ \mathrm{s}. \]

The ultimate torsional strength is 3 kg/mm². Based on the results of torsion testing and investigation of the fracture character, an area of friction-welding conditions was constructed for blanks made of R6M5 steel with structural steel 45 for a diameter of 11 mm (Fig. 4); for a diameter of 20 mm (Fig. 5); and for a diameter of 22 mm (Fig. 6).

Fig. 3. Graphs of the change in the welding allowance for Ø22 mm blanks of R6M5 steel with steel 45 as a function of \(t_n\), \(P_n\), \(P_p\)

Fig. 4. Area of recommended friction-welding conditions for Ø11 mm blanks of R6M5 steel with steel 45

Fig. 5. Area of recommended friction-welding conditions for Ø20 mm blanks of R6M5 steel with steel 45

Analyzing the investigated friction-welding conditions for end tools Ø 10–22 mm made of tungsten-molybdenum R6M5 steel with con-

with structural steel 45, welding parameters were selected under which the following are obtained:

1. Satisfactory strength of the welded joint.
2. The highest productivity.
3. The lowest consumption of high-speed steel.

The recommended parameters are summarized in Table 1.

Fig. 6. Region of recommended friction-welding parameters for blanks Ø 22 mm made of R6M5 steel with steel 45

Table 1

Friction-welding parameters for end tools Ø 10–22 mm made of tungsten-molybdenum steel R6M5 with structural steel 45 on the MOD MF-327 semiautomatic machine

Conclusions

1. Based on the results of torsion testing and investigation of the nature of fractures, regions of recommended friction-welding parameters were constructed for blanks Ø 10–22 mm made of R6M5 steel with structural steel 45.
2. Optimal friction-welding parameters have been established for blanks Ø 10–22 mm made of R6M5 steel with steel 45.

References

1. Yu. A. Geller. Tool Steels. Metallurgiya, 1968.
2. VNII. Technology for Welding Blanks of Metal-Cutting Tools. Moscow, 1966.