Bimetals-SNALLOY
Bimetal: Definition, Properties, and Applications
Many domestic, commercial, and industrial processes rely on thermostatic bimetals for electricalormechanicalactuationapplications.Theycanbefoundinmanycontrolswitches such as early thermostats, clocks, circuit breakers, and electricalappliances.
What is a bimetal?
A bimetal or thermostatic metal is a sheet or strip of two or more composite materials having different coefficients of linear thermal expansion bonded by riveting, brazing or welding. The material with the larger coefficient of thermal expansion (CTE) is considered as the active component, and that of smaller CTE is the passive component. The active component usually has alloys containing iron, manganese, nickel, or chrome in varying amounts. Whereas on the passive side, invar is often chosen, an iron-nickel alloy containing 36% nickel. Some bimetals include a third layer of copper or nickel in between the active and passive sides in order to increase thermal conductivity and decrease the material's electricalresistivity.
Propertiesbimetal
Bimetals work with the propensity of metals to expand when heated, and contract when cooled.resultingchangecurvatureorbendinginresponsetemperaturechange, isafundamentalpropertyallthermostaticbimetals.Ineffecttemperaturechangeis converted into mechanical displacement. The behaviour of bimetals is predictable and repeatable. The components used for bimetals are selected for their temperature characteristics as well as their thermal conductivitystabilitystrengthworkabilityand electricalproperties.
Flexivity
fundamentalcharacteristicabimetalisflexivityalsoknownspecificcurvature.It is an important property of bimetals that is defined by the curvature change along its longitudinal axis. This is expressed:
Bimetal - Flexibility where
F= flexivity (°F-1) (SI:°C-1)*
R2,R1= radii of curvature of the active and passive sides, respectively (in) (SI: mm) T= thickness of the strip (in) (SI:mm)
T2,T1= temperatures (°F) (SI: °C) And for a simplebeam:
where
L= distance between support points (in) (SI: mm) B= movement (in) (SI:mm)
Image 1: Schematic Diagram of Test for Flexivity. Retrieved from Ref. 3
Radius of curvature
Moreover, the equation below shows the flexing or radius of curvature of a bimetal strip. Here, we can see the factors that influence the bimetal bending and its relationship [3]:
where
ρ= radius of curvature of the strip (in) (SI:mm)
α1= first strip coefficient of expansion (°F-1) (SI:°C-1)
α2= second strip coefficient of expansion (°F-1) (SI: °C-1) T0T1= temperatures (°F) (SI:°C)
E1= modulus of elasticity for first strip (psi) (SI:Pa)
E2= modulus of elasticity for second strip (psi) (SI: Pa) t1t2= thickness of each component (in) (SI:mm)
t= thickness of the bonded strip (in) (SI:mm)
n= E1/E2
m=t1/t2
This equation shows that the thermostatic bimetal bending is directly proportional to temperature change of the component strips and the difference in the CTE, and inversely proportionalthicknesscombinedstrips.radiuscurvatureisalsoaffected by the thickness ratio and the ratio of the moduli of elasticity of the twostrips.
Electrical resistivity and thermal conductivity
applicationswhereheatisgeneratedpassingelectriccurrentthroughabimetal, knowledge of the electrical resistivity and thermal conductivity as parameters for temperature change is important. This is true for many bimetals that are used as circuit breakers. For aresistorthe equation below shows how temperature rise can bederived:
where
ΔT= temperature rise (°C) I= current(A)
ε= electrical resistivity(µΩ)
θ= time(s)
c= specific heat capacity (J/g°C), estimated at 0.502 for all Bimetals d= density(g/cm3)
w= width(mm)
t= total thickness(mm)
By using the convenient conversion factors, a similar formula can be derived in English units.
Bimetal applications
Temperature indication
Bimetals are used for temperature indication as in the spiral or helix actuated pointer thermometers. Such thermometers help measure temperatures in offices, refrigerators, and even on aircraft wings. The bimetals of this type are usually 0.005 in (0.127 mm)
0.015in(0.381mm)thickandcoilisfittedpointerscaleitgeneratessufficient torque in order to move the pointerfreely.The temperature range covered by bimetals extends approximately between -50°F and 1000°F (-46°C and 538°C). Angular deflection rate is usually at 2.5-3° per degreeFahrenheit.
Temperature control
Bimetals are utilised as a means to control the temperature, as in room temperature thermostats.Insuchdevicesabimetalbladeholdsacurrent-carryingcontactpointthatis linked to a coupled static contact point. This allows for the automatic switching of circuits to control heating and cooling of electrical devices as the blade arches when a certain temperature is reached.
Tube and pipe couplings
For cryogenic, non-magnetic, and nuclear applications where metal properties must be switched reliably, bimetallic couplings are used to enable direct connection and transition for pipes and tubes with different CTEs. These fittings may also be used in other thermal transfer applications
Type | Flexivity | Deflection | Linearity temperature range | Permitted useful temperature range | Permitted maximal used temperature | Modulus of elasticity | Electrical resistivity | Density | |
10-90°C | 40-150°C | 20-100°C | °C | °C | °C | ≥N/mm2 (× 105) | µ Ω .c m | g / cm3 | |
10-6/°C | 10-6/°C | 10-6/°C | |||||||
5J20110 | 39.4(1±4%) | 37.6 | 20.5 | -20 to 200 | -70 to 260 | 260 | 1.13 | 112.2(1±4%) | 7.7 |
5J14140 | 28.6(1±4%) | 28.6 | 14.3 | -20 to 200 | -70 to 260 | 260 | 1.13 | 141.3(1±4%) | 7.5 |
5J15120 | 28.8(1±4%) | 28.3 | 15.1 | -20 to 240 | -70 to 300 | 310 | 1.22 | 124.8(1±4%) | 7.6 |
5J1480 | 27.0(1±4%) | 26.3 | 14.3 | -20 to 150 | -70 to 370 | 540 | 1.47 | 79.0(1±4%) | 8.2 |
5J1380 | 26.2(1±4%) | 26.2 | 13.8 | -50-100 | -80-350 | 450 | 1.47 | 80.0(1±4%) | 8.1 |
5J1580 | 28.5(1±4%) | 26 | 15.5 | -20 to 200 | -70 to 350 | 450 | 1.47 | 78.0(1±4%) | 8.1 |
5J1017 | 18.7(1±4%) | 18.5 | 10 | -20 to 180 | -70 to 400 | 470 | 1.52 | 16.9(1±4%) | 8.4 |
5J1413 | 27.0(1±4%) | 27 | 14.3 | -20 to 150 | -70 to 180 | 180 | 0.98 | 12.3(1±8%) | 8.3 |
5J1416 | 26.8(1±4%) | 26.7 | 14.2 | -20 to 180 | -70 to 250 | 260 | 0.98 | 16.1(1±4%) | 8.3 |
5J1070 | 21.6(1±4%) | 22 | 11.4 | +90~320 | -70 to 540 | 540 | 1.52 | 69.0(1±4%) | 8.11 |
5J0756 | 13.1(1±4%) | 12.9 | 7.8 | -0-400 | -70 to 500 | 500 | 1.52 | 56.0(1±4%) | 8.2 |
5J1306A | 26.0(1±4%) | 26 | 13.8 | -20 to 150 | -70 to 200 | 400 | 1.22 | 5.84(1±7%) | 8.35 |
5J1306B | 25.6(1±4%) | 24.3 | 13.5 | -20 to 150 | -70 to 260 | 260 | 1.22 | 5.8(1±7.5%) | 8.38 |
5J1309A | 27.0(1±4%) | 27 | 14.32 | -20 to 150 | -70 to 200 | 400 | 1.22 | 9.0(1±7%) | 8.3 |
5J1309B | 26.3(1±4%) | 25.6 | 13.9 | -20 to 150 | -70 to 260 | 260 | 1.22 | 9.0(1±7.5%) | 8.25 |
5J1411A | 27.6(1±4%) | 27.6 | 14.9 | -20 to 150 | -70 to 200 | 400 | 1.22 | 10.5(1±7%) | 8.2 |
5J1411B | 26.0(1±4%) | 25.9 | 14 | -20 to 150 | -70 to 260 | 370 | 1.22 | 11.0(1±7%) | 8.25 |
5J1417A | 27.6(1±4%) | 27.6 | 14.9 | -20 to 150 | -70 to 200 | 400 | 1.22 | 17.0(1±10%) | 8.2 |
5J1417B | 26.6(1±4%) | 25.9 | 14.1 | -20 to 150 | -70 to 260 | 370 | 1.22 | 16.6(1±5%) | 8.2 |
5J1320A | 23.4(1±4%) | 23.4 | 13.3 | -20 to 150 | -70 to 200 | 450 | 1.52 | 20.0(1±8%) | 8.13 |
5J1320B | 23.6(1±4%) | 22.9 | 12.3 | -20 to 150 | -70 to 370 | 480 | 1.52 | 20.8(1±5%) | 8.3 |
5J1325A | 26.1(1±4%) | 26.1 | 13.9 | -20 to 150 | -70 to 200 | 450 | 1.52 | 25.0(1±8%) | 8.3 |
5J1325B | 24.7(1±4%) | 23.9 | 13.1 | -20 to 150 | -70 to 370 | 480 | 1.52 | 24.9(1±5%) | 8.3 |
5J1430A | 27.5(1±4%) | 27.5 | 14.8 | -20 to 150 | -70 to 200 | 450 | 1.52 | 30.0(1±7%) | 8.3 |
5J1430B | 25.4(1±4%) | 24.7 | 13.5 | -20 to 150 | -70 to 370 | 480 | 1.52 | 29.1(1±5%) | 8.3 |
5J1433A | 25.6(1±4%) | 25.5 | 14.6 | -20 to 150 | -70 to 200 | 480 | 1.52 | 33.0(1±7%) | 8.2 |
5J1433B | 25.9(1±4%) | 25.2 | 13.7 | -20 to 150 | -70 to 370 | 480 | 1.52 | 33.2(1±5%) | 8.2 |
5J1435A | 27.5(1±4%) | 27.5 | 14.8 | -20 to 150 | -70 to 200 | 450 | 1.52 | 35.0(1±7%) | 8.25 |
5J1435B | 25.1(1±4%) | 25.2 | 14 | -20 to 150 | -70 to 200 | 440 | 1.52 | 35.2(1±5%) | 8.2 |
5J1440A | 27.5(1±4%) | 27.5 | 14.8 | -20 to 150 | -70 to 200 | 450 | 1.52 | 40.0(1±7%) | 8.2 |
5J1440B | 26.5(1±4%) | 25.7 | 14 | -20 to 150 | -70 to 370 | 480 | 1.52 | 41.6(1±5%) | 8.2 |
5J1445A | 27.4(1±4%) | 27.8 | 14.4 | -20 to 150 | -70 to 200 | 440 | 1.52 | 45.2(1±7%) | 8.2 |
5J1445B | 26.5(1±4%) | 25.2 | 14.1 | -20 to 150 | -70 to 370 | 470 | 1.52 | 45.1(1±5%) | 8.2 |
5J1450A | 25.3(1±4%) | 25.6 | 14.5 | -20 to 150 | -70 to 200 | 450 | 1.52 | 50.3(1±7%) | 8.2 |
5J1450B | 25.1(1±4%) | 25.2 | 14.01 | -20 to 150 | -70 to 370 | 440 | 1.52 | 49.8(1±5%) | 8.2 |
5J1455A | 27.6(1±4%) | 27.6 | 14.9 | -20 to 150 | -70 to 200 | 450 | 1.47 | 55.0(1±7%) | 8.2 |
5J1455B | 25.2(1±4%) | 25.1 | 14.2 | -20 to 150 | -70 to 200 | 440 | 1.47 | 55.2(1±5%) | 8.2 |
5J1075 | 20.1(1±4%) | 20.2 | 10.8 | -20 to 200 | -70 to 200 | 450 | 1.66 | 75.1(1±7%) | 8 |
5J1085 | 19.7(1±4%) | 19.8 | 10.6 | -20 to 200 | -20 to 400 | 440 | 1.6 | 86.0(1±5%) | 8 |
Regular size:0.1~1.2mm*1~200mm Thickness:0.1/0.12/0.13/0.14/0.15/0.18/0.2/0.3/0.35/0.4/0.5/0.6/0.8/1.0/1.2 mm | ||||
Type | Alloy grade of the combination layer | Characters of bimetallic strip | ||
High expansion layer | Intermediate layer | Low expansion layer | ||
5J20110 | Mn75Ni15Cu10(Mn72Ni10Cu18) | - | Ni36 | High sensitivity High resistance Suitable for mediumtemperature |
5J14140 | Mn75Ni15Cu10(Mn72Ni10Cu18) | - | Ni36 | Medium sensitivity High resistance Suitable for mediumtemperature |
5J15120 | Mn75Ni15Cu10(Mn72Ni10Cu18) | - | Ni45Cr6 | Medium sensitivity High resistance Suitable for mediumtemperature |
5J1480 | Ni22Cr3 | - | Ni36 | Medium sensitivity Medium resistance Suitable for medium temperature |
5J1380 | Ni19Mn7 | - | Ni34 | Medium sensitivity Medium resistance Suitable for medium temperature |
5J1580 | Ni20Mn6 | - | Ni36 | Medium sensitivity Medium resistance Suitable for medium temperature |
5J1017 | Ni | - | Ni36 | Medium sensitivity Low resistance Suitable for medium temperature |
5J1413 | Cu62Zn38 | - | Ni36 | Medium sensitivity Low resistance High heatcondution |
5J1416 | Cu62Zn38 | - | Ni36 | Medium sensitivity Low resistance High heatcondution |
5J1070 | Ni19Cr11 | - | Ni42 | Medium sensitivity Suitable for higher temperature |
5J0756 | Ni22Cr3 | - | Ni50 | Low sensitivity Suitable for higher temperature |
5J1306A | Ni20Mn6 | Cu | Ni36 | Resistance series |
5J1306B | Ni22Cr3 | Cu | Ni36 | Resistance series |
5J1309A | Ni20Mn6 | Cu | Ni36 | Resistance series |
5J1309B | Ni22Cr3 | Cu | Ni36 | Resistance series |
5J1411A | Ni20Mn6 | Cu | Ni36 | Resistance series |
5J1411B | Ni22Cr3 | Cu | Ni36 | Resistance series |
5J1417A | Ni20Mn6 | Cu | Ni36 | Resistance series |
5J1417B | Ni22Cr3 | Cu | Ni36 | Resistance series |
5J1320A | Ni20Mn6 | Ni(Cu) | Ni36 | Resistance series |
5J1320B | Ni22Cr3 | Ni(Cu) | Ni36 | Resistance series |
5J1325A | Ni20Mn6 | Ni | Ni36 | Resistance series |
5J1325B | Ni22Cr3 | Ni | Ni36 | Resistance series |
5J1430A | Ni20Mn6 | Ni | Ni36 | Resistance series |
5J1430B | Ni22Cr3 | Ni | Ni36 | Resistance series |
5J1433A | Ni20Mn6 | Ni | Ni36 | Resistance series |
5J1433B | Ni22Cr3 | Ni | Ni36 | Resistance series |
5J1435A | Ni20Mn6 | Ni | Ni36 | Resistance series |
5J1435B | Ni22Cr3 | Ni | Ni36 | Resistance series |
5J1440A | Ni20Mn6 | Ni | Ni36 | Resistance series |
5J1440B | Ni22Cr3 | Ni | Ni36 | Resistance series |
5J1445A | Ni20Mn6 | Ni | Ni36 | Resistance series |
5J1445B | Ni22Cr3 | Ni | Ni36 | Resistance series |
5J1450A | Ni20Mn6 | Ni | Ni36 | Resistance series |
5J1450B | Ni22Cr3 | Ni | Ni36 | Resistance series |
5J1455A | Ni20Mn6 | Ni | Ni36 | Resistance series |
5J1455B | Ni22Cr3 | Ni | Ni36 | Resistance series |
5J1075 | Ni16Cr11 | - | Ni20Co26Cr8 | Anti-corrosion Highstrength |
5J1085 | Mn15Ni10Cr | - | Ni36Nb | Anti-corrosion Highstrength |
Type | Heat treatment | ||
Treatment temperature/°C | Heat preservation time / h | Cooling method | |
5J20110 | 260~280 | 1~2. | Air cooling |
5J14140 | 260~280 | ||
5J15120 | 260~280 | ||
5J1480 | 300~320 | ||
5J1380 | 300~320 | ||
5J1580 | 300~320 | Air cooling | |
5J1017 | 300~320 | ||
5J1413 | 180~200 | ||
5J1416 | 180~200 | ||
5J1070 | 380~400 | ||
5J0756 | 400~420 | ||
5J1306A | 250~270 | ||
5J1306B | 250~270 | ||
5J1309A | 250~270 | ||
5J1309B | 250~270 | ||
5J1411A | 250~270 | ||
5J1411B | 250~270 | ||
5J1417A | 250~270 | ||
5J1417B | 250~270 | ||
5J1320A | 300~320 | Air cooling | |
5J1320B | 300~320 | ||
5J1325A | 300~320 | ||
5J1325B | 300~320 | ||
5J1430A | 300~320 | ||
5J1430B | 300~320 | ||
5J1433A | 300~320 | ||
5J1433B | 300~320 | ||
5J1435A | 300~320 | ||
5J1435B | 300~320 | ||
5J1440A | 300~320 | ||
5J1440B | 300~320 | ||
5J1445A | 300~320 | ||
5J1445B | 300~320 | ||
5J1450A | 300~320 | Air cooling | |
5J1450B | 300~320 | ||
5J1455A | 300~320 | ||
5J1455B | 300~320 | ||
5J1075 | 400~420 | ||
5J1085 | 400~420 | ||
Type GB/T4461 | China Type | German Type | ASTM Type |
5J20110 | 5J11 | TB 208/110 | TM2 |
5J14140 | R40 | TB140/140 | TM8 |
5J15120 | 5J14 | ||
5J1480 | 5J18 | TB140/80 | TM1 |
5J1380 | 5J19 | ||
5J1580 | 5J16 | TB155/78 | |
5J1017 | 5J24 | TM22 | |
5J1413 | |||
5J1416 | |||
5J1070 | 5J23 | TM6 | |
5J0756 | 5J25 | TM5 | |
5J1306A | R6 | TB130/06 | |
5J1306B | |||
5J1309A | R9 | TB130/09 | |
5J1309B | |||
5J1411A | R11 | TB150/11 | |
5J1411B | |||
5J1417A | 5J101 | ||
5J1417B | TM9 | ||
5J1320A | R20 | ||
5J1320B | TM10 | ||
5J1325A | R25 | TB127/25 | |
5J1325B | TM11 | ||
5J1430A | R30 | ||
5J1430B | TM12 | ||
5J1433A | R33 | ||
5J1433B | TM13 | ||
5J1435A | R35 | ||
5J1435B | |||
5J1440A | R40 | TB138/42 | |
5J1440B | TM14 | ||
5J1445A | |||
5J1445B | |||
5J1450A | |||
5J1450B | |||
5J1455A | |||
5J1455B | R55 | TM16 | |
5J1075 | |||
5J1085 |
