OAO “AVTOVAZ”
Technical & Engineering BU
Laboratory & Trial Tests / Minutes of Meeting No 12034 – 8
For Research Works / Laboratory of Tool Steels
Dated from 04.05.2005
Reference Documents: / Without official notes
Manufacturer / OOO “Novyie Technologiye”, Samara, RF
Subject of research / Welded Blanks OOO “Novyie Technologiye”
2 pcs. made of P18 and 40X steel;
Welded Blanks prepared for welding
OAO “AVTOVAZ” Engineering Center
1 pc. made of P6M5 and 4-X steel
1 pc. made of P18 and 40X steel
Reason for submission to reclamation analysis / Harden blank with reheat temperature for welding
Method of diffusion welding
Reheat temperature = (0,8 – 0,9) of melting point for steel
Reheat temperature = 1200oC
Drawing requirements / Technology requirements
Mark of material / Hardness / Mark of material / Hardness

Results of Researches

Welded Blanks OOO “Novyie Technologiye”

  1. Micro-structure:
  2. Steel P18 – austenitic grain 11 (10)
  3. Steel 40X – austenitic grain 2-3
  4. Decarburization is exposed on the cylindrical surface of a blank made of steel 40X (near destruction area). The decarburized layer is ~ 80 µm deep (see fig 1).
  5. Quality of weld (except the decarburized section near cylindrical surface which contributes to destruction) is good – pores or incomplete penetration are missing.
  1. Hardness of steel P18 (core): 851 HV2 (~63,5 HRC)
  1. Distribution of micro-hardness from the weld surface to the core:

Place of measurement / L, µm / HK0,1 / Depth of decarburized layer
т.1 20
26
50
64
74
82
core / 164
235
380
430
495
535
535 / ~ 82 µm

Fig 1. / т.2 10
20
28
core / 880
880
880
880 / No lowering of micro-hardness
  1. Additional researches (after annealing):

4.1.Micro-structure:

-P18 – sorbite + carbides;

-40X – ferrite + lamellar pearlite. Decarburization is exposed from the weld. The decarburized layer is ~ 400 µm deep. Ring crack (or incomplete penetration) is up to 180µm deep in outside diameter of the weld (see fig. 2)

4.2.Distribution of micro-hardness from the weld surface to the core:

Place of measurement / L, µm / HK0,1 / Depth of decarburized layer
т.1 20
74
120
170
220
310
352
400
440
480… / 128
126
120
130
130
132
134
170
200
205 / ~ 440 µm

Fig 2 / т.2 20
54
80 / 365
365
365 / No

Welded blanks prepared for welding in OAO “AVTOVAZ” Engineering Center

After-welded blanks were subject to additional low-temperature annealing - heating up to 720oC, time delay 3 hours, cooling with a burner

P6M5 – 40X steel

1.1.Micro-structure:

-P6M5 – sorbite + carbides;

-40X – ferrite + lamellar pearlite. Decarburization is exposed on the cylindrical blank made of 40X steel. The decarburized layer is ~ 400 µm deep.

1.2.Hardness:

- P6M5 - 609 HV2 (~ 54,5 HRC)

- 40X- 207 HV2 (~ 18 HRC)

1.3.Distribution of micro-hardness from the weld surface to the core:

Place of measurement / L, µm / HK0,1 / Depth of decarburized layer
40X / 20
30
54
70
90
104
core / 198
205
212
212
230
230
230 / ~ 90 µm
P6M5 / 10
32
50
core / 700
700
700
700 / no

P18-40X steel

2.1. Micro-structure:

-P18 – sorbite + carbides;

-40X – ferrite + lamellar pearlite. Decarburization is exposed on the cylindrical blank made of 40X steel. The decarburized layer is ~ 200 µm deep.

2.2.Hardness:

- P18- 659 HV2 (~ 56,5 HRC)

- 40X- 219 HV2 (~ 20 HRC)

2.3.Distribution of micro-hardness from the weld surface to the core:

Place of measurement / L, µm / HK0,1 / Depth of decarburized layer
40X / 20
40
60
84
100
122
core / 210
205
220
220
230
230
230 / ~ 100 µm
P18 / 10
20
32
core / 730
730
730
730 / no

Conclusions:

  1. Weld quality is good.
  2. To better prepare high-speed steel to further hardening it is necessary to optimize annealing of blanks after welding.