US2024401182A1PendingUtilityA1
Method for optimising the roughness of a rolling mill roll by means of high-speed thermal spraying
Est. expiryOct 4, 2041(~15.2 yrs left)· nominal 20-yr term from priority
Inventors:Gregorio Fuentevilla Diaz
C23C 4/18C23C 4/16C23C 4/067C23C 4/129B21B 27/005C23C 4/04B21B 2267/10B21B 27/032B21B 27/02
34
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Claims
Abstract
The invention relates to a method for coating a mill roll by means of thermal spraying of a powder by means of a spraying column to form an isotropic roughness (Ra) on the surface of said mill roll, wherein the mill roll rotates at a speed (Vr) about the longitudinal axis thereof and the spraying column moves translationally at a speed (Vt), depositing the material in a helicoidal way. After establishing a granulometry (G) of powder to be sprayed, an objective roughness (Ra) and an objective thickness (t) of the coating, the corresponding feed flow (Fr) of powder is determined in an empirical table which shows the objective roughness (Ra) on the basis of the feed flow (Fr) and the granulometry (G) according to a pre-established formula, after which the rotational speed (Vr) and the translational speed (Vt) are defined from an equation that relates the objective coating thickness (t) as a function of the defined feed flow (Fr), the translational speed (Vt) and the rotational speed (Vr).
Claims
exact text as granted — not AI-modified1 . A method for optimising the roughness of a rolling mill roll by means of high-speed thermal spraying, more specifically thermal spraying of a powder by means of a spraying column to form an isotropic roughness (Ra) on the surface of said mill roll, wherein the mill roll rotates at a rotational speed (Vr) about the longitudinal axis thereof and the spraying column moves translationally at a translational speed (Vt), parallel to the axis of the mill roll to deposit the material according to a helical figure, wherein the following operational phases are established:
a) establishing a granulometry (G) of powder to be sprayed, b) establishing an objective roughness (Ra) and an objective thickness (t) of the coating, c) finding the corresponding feed flow (Fr) of powder in an empirical table which shows the objective roughness (Ra) on the basis of the feed flow (Fr) and the granulometry (G) according to the formula:
Ra
=
η
·
(
A
(
G
)
·
Fr
+
(
G
)
)
where η is the efficiency of the process that depends on the type of equipment to be used and A (G) and B (G) are functions of the granulometry of the powder (G),
d) defining the rotational speed (Vr) and the translational speed (Vt) from an equation that relates the objective coating thickness (t) as a function of the defined feed flow (Fr), the translational speed (Vt) and the rotational speed (Vr), according to the formula:
t
=
η
·
Fr
·
N
Vr
·
Vt
·
ρ
where N are the revolutions per minute of the mill roll and p is the density of the spraying powder, while the ratio between the width of the spray cone (d) and the pitch per turn (p) of the screw is greater than one.
2 . The method for optimising the roughness of a rolling mill roll by means of high-speed thermal spraying according to claim 1 , wherein a HVAF thermal spraying method is used, and wherein the empirical table for calculating the desired roughness (Ra) based on the granulometry of the powder (G) and the powder feed flow (Fr) being:
Average granulometry of the Powder (μm)
10
15
20
25
30
35
40
Feed
2
0.8
1.4
1.9
2.2
2.5
2.7
2.7
flow
4
1.1
1.7
2.2
2.5
2.8
3.0
3.0
(kg/h)
6
1.4
2.0
2.5
2.8
3.1
3.3
3.3
8
1.7
2.3
2.8
3.1
3.4
3.6
3.6
10
2.0
2.6
3.1
3.4
3.7
3.9
3.9
12
2.3
2.9
3.4
3.7
4.0
4.2
4.2
14
2.6
3.2
3.7
4.0
4.3
4.5
4.5
16
2.9
3.5
4.0
4.3
4.6
4.8
4.8
18
3.2
3.8
4.3
4.6
4.9
5.1
5.1
20
3.5
4.1
4.6
4.9
5.2
5.4
5.5
22
3.8
4.4
4.9
5.2
5.5
5.7
5.8
3 . The method for optimising the roughness of a rolling mill roll by means of high-speed thermal spraying according to claim 1 , wherein a HVOF thermal spraying method is used, and wherein the empirical table for calculating the desired roughness (Ra) based on the granulometry of the powder (G) and the powder feed flow (Fr) being:
Average granulometry of the Powder (μm)
25
30
35
40
45
50
Feed
8
3.7
4.1
4.3
4.4
4.4
4.4
flow
10
4.1
4.4
4.6
4.8
4.8
4.8
(kg/h)
12
4.5
4.8
5.0
5.1
5.1
5.1
14
4.8
5.1
5.4
5.5
5.5
5.5
16
5.2
5.5
5.7
5.8
5.8
5.8
18
5.5
5.9
6.1
6.2
6.2
6.2
20
5.9
6.2
6.4
6.5
6.6
6.6
22
6.3
6.6
6.8
6.9
6.9
7.0
4 . The method for optimising the roughness of a rolling mill roll by means of high-speed thermal spraying according to claim 1 , wherein the spray powder contains hard particles with dimensions less than 1 μm and wherein the objective final roughness (Ra) depends on the average granulometry of the powder (G) according to the following rule:
Roughness-Ra
Average granulometry of
(μm)
the Powder-G (μm)
Ra ≤ 1 μm
G < 20 μm
1 μm < Ra ≤ 4 μm
G < 30 μm
4 μm < Ra
G < 50 μm.
5 . The method for optimising the roughness of a rolling mill roll by means of high-speed thermal spraying according to claim 1 , wherein the number of peaks (RPc) of the coating surface does not exceed a value related to the roughness (Ra) according to the following formula:
RPc
≤
88
+
47
·
Ln
(
Ra
)
6 . The method for optimising the roughness of a rolling mill roll by means of high-speed thermal spraying according to claim 1 , wherein the number of peaks (RPc) is obtained by an additional surface treatment step consisting of reducing the height and number of peaks by mechanical, thermal, chemical or electrochemical ablation/elimination, for roughness less than 2 μm.Join the waitlist — get patent alerts
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