JPS62147681A - Sheathed heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a sheathed heater that is applied as a heating source in a wide range of product fields such as general cooking utensils and heating appliances, and particularly relates to a sheathed heater that uses long-life and inexpensive heating wires. It is related to heaters.

Conventional technology Since sheathed heaters are simple, safe, and have excellent corrosion resistance, they are widely used as a heating source for cooking and heating appliances such as ovens, microwave ovens, rice cookers, hot grates, and electric stoves. has been done.

This sheathed heater generally has a coiled heating wire with terminal bars at both ends inserted into the center of a metal pipe.
This metal vibrator is manufactured by filling it with electrically insulating powder made of magnesia powder and then rolling it to reduce its diameter.

Conventionally, JI is used as the heating wire for such sheathed heaters.
Heating wires specified in S, namely NcHw and FCH
W has been used.

This is because these heating wires have a stable lifespan when used in the atmosphere, and are also stably supplied commercially.

Problems to be Solved by the Invention As mentioned above, the sheathed heater has NCHW and FC).
IW is used, and FC is used for low temperatures below about 400'C.
HW2 is NCH for medium temperature use of approximately 400 to 650°C.
NCHWl is generally used for high temperature applications where W2 is approximately 660'C or higher. According to JIS, the maximum operating temperature of heating wires in the atmosphere is N CHW 1 O and F
CHW2 is about 110oC, and FCHW2 is about 1
Q00'C, which was clearly different from the case of a sheathed heater, and the lifespan of a sheathed heater was shorter than that of a heating wire in the atmosphere.

In terms of cutting costs, NCHW has a high material cost because it contains a large amount of Ni and Cr, while FCHW has poor wire drawability and is also expensive.

Furthermore, when sheathed heaters are used in cooking and heating appliances, fast heating properties are required, but NCHW and FCHW have a small resistance temperature change rate (generally around 1.1), so they are inferior in quick heating properties and have poor self-control properties. was also inferior.

As described above, the reality is that conventional sheathed heaters using heating wires have various problems. The object of the present invention is to provide an inexpensive sheathed heater having the following characteristics.

Means for Solving the Problems In order to solve the above problems, the present invention provides heating wires for sheathed heaters that contain carbon of 0.07% or less and Si of 2.00 to 0.07%.
3. O0%, Mn 0.50% or less, P 0.040%
Below, S is 0.030% or less, G r7'): 18.
00 to 19.00%, residual force F e using a canal alloy.

Function: The lifespan of conventional heating wires differs greatly between the atmosphere and in a sheathed heater, and is shorter in a sheathed heater. This shows that the atmosphere surrounding the heating wire is different.

That is, in conventional heating wires, oxidation is caused by oxygen in the atmosphere, while in NCHW, Cr2O5 is oxidized.

In FCHW, the life of the heating wire is extended by forming a dense oxide film of mu e20s and suppressing the reaction between the heating wire and oxygen, but in the sheathed heater, there is a lack of oxygen, and the The oxide film that should be formed is not sufficiently formed, and conversely, Cr in the heating wire is NG) in IW, but in FCHW.
In this case, the mu e decreased in the metallic state, causing the heating wire to become thinner and the insulation of the sheathed heater to deteriorate, resulting in a shortened lifespan.

The heating wire of the present invention has a Cr content lower than that of NCHWl, equivalent to FCHW2 and FCHW2, and does not contain any kl. Therefore, unlike FCHW2, there is no extreme decrease in life caused by kl, and NCHWl and FCH
It has approximately the same lifespan as W2.

On the other hand, in terms of cost, since it does not contain Ae, it has excellent wire drawing processability, and because the expensive Ni content is low, the material cost is low, so it is lower in cost than conventional heating wires.

Furthermore, the heating wire of the present invention has a resistance temperature change rate of about 1.25 in the range from room temperature to e00'c, 1.011 for NC1HW1, 1.071 for FCHW2, and 1.071 for FCHW2.
This is larger than 1.137 of No. 2, indicating that it has rapid heating properties and self-regulating properties.

The reasons for limiting the composition of the heating wire are as follows.

If the content of C is too high, it will cause a decrease in service life, decrease in workability, and decrease in weldability.
In order to increase the resistance at room temperature, control the resistance temperature change rate to an appropriate value, and improve the oxidation resistance, it should be 2.004 or more, and 3.00% in consideration of the decrease in workability. The following was made.

Although Mn is harmful to the heating wire, it is necessary for producing and processing the alloy, so it was set to 0.50% or less.

Since P and S are harmful to the heating wire, it is desirable that they be as small as possible, but due to technical difficulties, they were set to 0.040% or less and 0.030% or less, respectively. Cr
is undesirable in a non-oxidizing atmosphere because it leads to a shortened lifespan, but in the case of a sheathed heater, it is a weakly oxidizing atmosphere and oxidation resistance is somewhat desirable, so it is 18.00 to 19.
It was set as 00.

EXAMPLE Hereinafter, an example of the present invention will be described based on FIGS. 1 to 4. A coiled heating wire with terminal rods at both ends was inserted into a metal pipe made of corrosion-resistant and heat-resistant superalloy NCF300, After filling with electrical insulating powder made of magnesia powder, the tube was rolled to reduce its diameter, and then bent and pressed into a U-shape to produce a U-shaped sheathed heater with an outer diameter of 6.6 mm and a total length of 600 mm. The heating wire used for this had an outer diameter of 0.5 mm, and its composition is shown in the following table.

Table Composition of Heating Wire (H) When a single heating wire (outer diameter φ0.5 mm) is subjected to a life test in the air with a heating and cooling cycle of 2 minutes on/2 minutes off at a heating wire temperature of 12oO℃, the first The lifespan values were shown as shown in the figure. FIG. 1 shows the average lifetime of five samples each.

As is clear from FIG. 1, the lifespan of the heating wires in the atmosphere was in the order of NCHW2)FCHW2:>Heating wires used in the present invention. This is because NCHW2 and FCHW2 have excellent oxidation resistance, which reduces thinning due to repeated cooling and heating cycles, resulting in a long life.

Figure 2 shows the results of a lifespan test on the sheathed heater manufactured above.The lifespan test was performed at a surface temperature of 8oC and an accelerated test using a cooling/heating cycle of 20 minutes of electricity/10 minutes of rest. carried out.

F, which is generally used for low temperatures (approximately 400°C or less)
CHW2 has a short lifespan, and the sheathed heater of the present invention is NC.
It showed a lifespan value close to that when HW2 was used. This is FC
HW2 contains human e, which quickly diffuses inside the heating wire inside the sheathed heater, and human e with high vapor pressure is selectively consumed, causing the heating wire to become thinner extremely quickly.

Since the heating wire of the sheathed heater of the present invention does not contain A2, it has a longer lifespan than FCHW2, but it has a slightly shorter lifespan than NCHW2 because it is basically inferior in oxidation resistance.

As described above, the sheathed heater of the present invention has a longer life compared to the sheathed heater using FCHW2, and
It was found that the 7-Z heater has a lifespan close to that of a sheathed heater using a 7-Z heater, which has an excellent lifespan up to the medium temperature range (approximately 600°C).

Furthermore, Fig. 3 shows a comparison of the rising temperatures at the initial stage of energization using the aforementioned sheathed heater (designed with energization stability special conditions of 6oOW/1oOv).As is clear from this Fig. 3, NGI ( There is no difference between W2 and FCHW2, but the sheathed heater of the present invention starts up quickly and has a
Comparing the time to reach °C, it was found that NCHW2 and FCHW2 took about 3 minutes, while the present invention took about 2.4 minutes, indicating that it has excellent rapid heating properties.

FIG. 4 shows the relationship between the temperature of the heating wire in the sheathed heater and the rate of change in resistance. In the case of the present invention, it was found that the rate of change in resistance was large and it had self-control. Therefore, even if the heater used in the water is left unheated or a high voltage is mistakenly applied, it is unlikely to reach a high temperature, and accidents such as wire breakage can be prevented.

Effects of the Invention As is clear from the above explanation, according to the sheathed heater of the present invention, the heating wire has C of 0.07 or less, Si of 2.00 to 3.00%, and Mn of 0.5. qb or less, P is 0.040% or less, and S is 0.030% or less.

Since it uses an alloy consisting of 18.00-19.00% Cr and the balance Fe, it has a long life and excellent heat-up properties.
Furthermore, it is possible to provide an excellent sheathed heater with self-control properties.

[Brief explanation of drawings]

Fig. 1 is a graph showing the life of a single heating wire in the atmosphere, Fig. 2 is a graph showing the life of a sheathed heater in an embodiment of the present invention, Fig. 3 is a graph showing the rise characteristics of the sheathed heater, FIG. 4 is a graph showing the relationship between the heating wire temperature and the rate of change in resistance of the same sheathed heater. Name of agent: Patent attorney Toshio Nakao and one other person Wc
Figure 1 Figure 2 Figure 3 Figure 4 o zao atto 7
1ri. Electric heating printing (°su)

Claims (1)

[Claims] As a heating wire, C is 0.07% or less and Si is 2.00~
3.00%, Mn 0.50% or less, P 0.040%
Below, S is 0.030% or less, Cr is 18.00 to 19
．． 1. A sheathed heater characterized by using an alloy consisting of 0.00% Fe and the remainder Fe.