JPH04329823A - Production of mandrel made of ductile cast iron for crawler - Google Patents

Abstract

PURPOSE:To attain heat treatment free from reheating by pouring a molten ductile cast iron into a mold to cast a mandrel for crawler shaking out the resulting casting at the time when the temp. of the mandrel lies in a specific temp. region, and performing forced cooling. CONSTITUTION:The mandrel is produced by casting a molten ductile cast iron of prescribed composition in a mold. At this time, whether molten metal is solidified and the temp. of the mandrel in high temp. state lies in the austenite region (1000-850 deg.C) or in the coexistence region of austenite and ferrite is measured by a proper means. The casting is shaked out at the proper time. After the casting is taken out from the mold, forced cooling is done. It is preferable that the ductile cast iron has a composition consisting of, by weight ratio, 3.20-4.00% C, 2.20-3.00% Si, 0.05-0.60% Mn, <=0.025% S, <=0.070% P, 0.020-0.060% Mg, and the balance Fe with inevitable impurities.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a core metal made of ductile cast iron, which is embedded in an elastic crawler track of a crawler used in civil engineering machinery, agricultural machinery, etc.

0002

2. Description of the Related Art Recently, elastic tracks have been widely used as endless tracks for crawlers used in agricultural machinery and the like. As shown in Fig. 1, this elastic crawler track has core metals embedded at intervals in the longitudinal direction, and the core metals include a guide lug that protrudes from the inner surface of the crawler main body, and a guide lug that is embedded within the main body and extends on both sides thereof. The crawler track body has a flat plate-shaped wing portion, and a tensile member made of steel wire is embedded in the crawler track body at a position below the core bar.

[0003] The core metal is manufactured from ductile cast iron or forged steel, and is usually subjected to heat treatment such as normalizing, quenching, and tempering to ensure the necessary hardness and strength. .

0004

[Problems to be Solved by the Invention] As mentioned above, ductile cast iron has properties similar to steel, and therefore, various other structures can be improved through heat treatment to improve its properties. , Conventional heat treatment employs a method in which the core metal is cooled to room temperature after casting, and then reheated at appropriate times to the heat treatment temperature, but this reheating is not preferable from an energy saving standpoint, and It was also not very favorable in terms of manufacturing cost.

[0005] In view of the above-mentioned circumstances, it is an object of the present invention to achieve energy saving by performing heat treatment without performing conventional reheating.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention casts a core metal for a crawler by pouring molten ductile cast iron into a mold, and the temperature of the core metal is in the austenite range or between austenite and ferrite. We adopted a configuration in which the mold is separated when it is in the coexistence region, and then forced cooling is performed using a cooling means.

[0007]

[Examples] Examples of the present invention will be described below. An example of the crawler core metal to which the present invention is applied is shown in FIGS. 1 and 2. Figure 1 is a cross-sectional view of the elastic track in the width direction, Figures 2A and B
are a plan view and a side view of the core metal. In both figures, reference numeral 1 denotes an endless elastic crawler track body made essentially of rubber, and core metals 2 are buried within this body 1 at intervals in the longitudinal direction. The core metal 2 has guide lugs 3, 3 protruding from the inner surface of the crawler belt main body 1, and flat plate-shaped wing portions 4, 4 embedded in the main body 1 and extending on both sides thereof. It goes without saying that the shape of the core metal 2 is not limited to that shown in the drawings. Such core metal is made of ductile cast iron.

The present invention is a method for manufacturing the above ductile cast iron core metal, in which molten ductile cast iron having the chemical composition shown in Table 1 below is poured into a mold to cast the core metal. The casting method is conventionally known.

[0009]

[Table 1]

Next, the cast molten metal solidifies, and the temperature of the high-temperature core metal reaches the austenite range (1000°C to 850°C).
°C) or the coexistence region of austenite and ferrite (
850°C to 750°C) using an appropriate measuring means, take the casting out of the mold by breaking the mold (opening the frame), and immediately cool it at a predetermined cooling rate with an appropriate cooling means. Forced cooling is performed at the base. At this time, as the cooling means, such as air cooling, blast cooling, cooling in oil, etc. can be adopted as appropriate. Note that normalizing, hardening, tempering, etc. can be performed as appropriate by selecting a cooling cycle. Therefore, in the present invention, if the mold is released and heat treated in the above-mentioned predetermined temperature range,
There is no need for reheating as in the past, and the energy saving effect is significant. In addition, if the temperature of the core metal after demolding falls below the specified temperature, even if it is charged into a furnace maintained at a temperature of around 900℃ as necessary, the energy required for this will be reduced by the energy required to cool it down to room temperature. Needless to say, this is far less than when reheating castings.

[0011] Specific examples of the present invention will be further explained below along with comparative examples. (Example 1) (Comparative Example 1) The core metal shown in Fig. 2 was cast using the ductile cast iron molten metal shown in Table 2, and the temperature of the core metal was
When the temperature reached 950°C, the mold was removed and cooled with air blast. Table 3
Figure 2 shows comparison values of the physical properties of the core metal as described above and that of the metal core that was cooled to room temperature without being disassembled, then reheated to 900°C, and blast cooled.

0012

[Table 2]

[0013]

[Table 3]

(Example 2) (Comparative Example 2) The core metal shown in FIG. 2 was cast using the ductile cast iron molten metal shown in Table 4, and the same treatment as in Example 1 was performed. The results are shown in Table 5.

[0015]

[Table 4]

[0016]

[Table 5]

(Example 3) (Comparative Example 3) The core metal shown in FIG. 2 was cast using the ductile cast iron molten metal shown in Table 6, and the temperature of the core metal was
When the temperature reached 920℃, the mold was removed, and then cooled in oil.
It was tempered at 400°C for 1 hour. On the other hand, after once cooling to room temperature without demolding, it was reheated to a temperature in the austenite region of 900°C, cooled in oil, and tempered. Table 7
is the comparison value of the physical properties of both.

[0018]

[Table 6]

[0019]

[Table 7]

(Example 4) (Comparative Example 4) The core metal shown in FIG. 2 was cast using the ductile cast iron molten metal shown in Table 8, and the temperature of the core metal was
When the temperature reached 920℃, the mold was removed and then heated to 260℃.
The material was quenched in a salt bath furnace maintained at a temperature of 100° C. to undergo isothermal transformation for 1 hour. On the other hand, it was cooled to room temperature without being unmolded, then reheated to a temperature in the austenite range (900°C), and quenched in a salt bath furnace maintained at 260°C to undergo isothermal transformation for 1 hour. Table 9 shows comparative values of physical properties between the two.

[0021]

[Table 8]

[0022]

[Table 9]

When examining the physical property comparison values in Tables 3, 5, 7, and 9 for Examples 1 to 4 and Comparative Examples 1 to 4 above, it is found that in each table, the maximum bending load (
There was almost no difference in the results (kg), deflection (mm), and hardness (HB), and the method of the present invention was able to achieve the maximum effect of energy saving without affecting the physical properties in any way.

[0024]

According to the present invention, a core metal for a crawler is cast by pouring molten ductile cast iron into a mold, and when the temperature of the core metal is in the austenite range or the coexistence range of austenite and ferrite, the mold is released, and then, By using a cooling method to perform forced cooling, it is possible to achieve energy savings while maintaining the physical properties of the core metal obtained by conventional manufacturing methods, and the process is also simplified, resulting in a significant reduction in manufacturing costs. The effect is significant.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view in the width direction of an elastic crawler belt.

FIG. 2 is a plan view and a side view of a core metal.

[Explanation of symbols]

1 Elastic track body 2 Core metal

Claims (12)

[Claims] Claim 1: A core metal for a crawler is cast by pouring molten ductile cast iron into a mold, and when the temperature of the core metal is in the austenite range or the coexistence range of austenite and ferrite, the mold is released, and then forced by cooling means. A method for manufacturing a core metal for a ductile cast iron crawler, which is characterized by cooling. 2. The chemical composition of the ductile cast iron molten metal is C: 3.20 to 4.00%, Si: 2.0% by weight.
20-3.00, Mn: 0.05-0.60%
, S: 0.025% or less, P: 0.07
0% or less, Mg: 0.020 to 0.060%
, the remainder being Fe and unavoidable impurities. [Claim 3] The chemical composition of the ductile cast iron molten metal is in weight percent, C: 3.20 to 4.00%, Si:
2.20-3.00, Mn: 0.05-0.6
0%, S: 0.025% or less, P:
0.070% or less, Mg: 0.020 to 0.0
60%, Cu: 0.20 to 1.0%, and the remainder Fe and unavoidable impurities. 4. The chemical composition of the ductile cast iron molten metal is in weight percent, C: 3.20 to 4.00%, Si:
2.20-3.00, Mn: 0.05-0.6
0%, S: 0.025% or less, P:
0.070% or less, Mg: 0.020 to 0.0
60%, Sn: 0.02 to 0.075%, and the remainder is Fe and unavoidable impurities. 5. The chemical composition of the molten ductile cast iron is in weight percent, C: 3.20 to 4.00%, Si:
2.20-3.00, Mn: 0.05-0.6
0%, S: 0.025% or less, P:
0.070% or less, Mg: 0.020 to 0.0
60%, Cu: 0.20-1.0%, Sn
The method for producing a core metal for a crawler made of ductile cast iron according to claim 1, wherein: 0.02 to 0.075%, the remainder being unavoidable impurities. 6. The method for producing a core metal for a ductile cast iron crawler according to claim 1, wherein the cooling means is air cooling or blast cooling. [Claim 7]Claim 1, wherein the cooling means is cooling in oil.
5. The method for manufacturing a core metal for a ductile cast iron crawler according to any one of items 5 to 5. 8. The method for producing a core metal for a ductile cast iron crawler according to claim 7, wherein the core metal for a crawler made of ductile cast iron is tempered at 300 to 600° C. after forced cooling. 9. The chemical composition of the ductile cast iron molten metal is, in weight percent, C: 3.20 to 4.00%, Si:
2.20-3.00, Mn: 0.05-0.6
0%, S: 0.025% or less, P:
0.070% or less, Mg: 0.020 to 0.0
60%, Mo: 0.30 to 0.65%, Ni: 0.31 to 1.20% per 25 mm with respect to the maximum wall thickness, the balance being Fe and inevitable impurities. Manufacturing method for core metal for crawlers. 10. The chemical composition of the ductile cast iron molten metal is, in weight percent, C: 3.20 to 4.00%, Si
:2.20-3.00, Mn:0.05-0.
60%, S: 0.025% or less, P
: 0.070% or less, Mg: 0.020 to 0.
060%, Mo: 0.30-0.65%, C
The method for producing a core metal for a ductile cast iron crawler according to claim 1, wherein u: 0.30 to 1.20%, the balance being Fe and unavoidable impurities. 11. The chemical composition of the ductile cast iron molten metal is, in weight percent, C: 3.20 to 4.00%, Si
:2.20-3.00, Mn:0.05-0.
60%, S: 0.025% or less, P
: 0.070% or less, Mg: 0.020 to 0.
060%, Mo: 0.30 to 0.65%, per 25 mm of maximum wall thickness, Ni: 0.31 to 1.20%,
The method for producing a core metal for a ductile cast iron crawler according to claim 1, comprising Cu: 0.30 to 1.20%, the balance being Fe and unavoidable impurities. 12. Molten ductile cast iron is poured into a mold to cast a core metal for a crawler, and when the temperature of the core metal is in the austenite range or the coexistence range of austenite and ferrite, the mold is released, and then the temperature is 230 to 550°C. Claims 9 to 1: quenching in an oil bath, salt bath, or fluidized bed furnace maintained at a temperature of 10 minutes to 3 hours to effect isothermal transformation.
1. The method for manufacturing a core metal for a ductile cast iron crawler according to item 1.