JPS6025498B2 - Steel for drilling cutting edges with excellent hot workability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an excavator cutting edge for use in civil engineering and construction machinery, etc., which has good toughness, toughness and wear resistance at high temperatures, and has excellent hot workability during manufacturing. Regarding steel.

The ripper point of a bulldozer is a typical example of an excavating cutting edge of a civil engineering construction machine, and the present invention is directed to various types of steel for excavating cutting edges that require similar conditions.

The present invention will be explained in detail below using Ripper Point as an example. Figure 1 shows an example of a ripper point. In the figure, 1 is a ripper point, and 2 is a ripper shank, which is attached to an excavation mechanism specially installed on a bulldozer and pushed into bedrock.

Accordingly, the mechanical properties of the steel material used for such drilling cutting edges are required to have a tensile strength of 150k9 or higher, a hardness of HRC of 50 or higher, and a Charpy impact value of 5k9 or higher. Ni-Cr-Mo based low alloy steel, as shown in G in Table 4, has been widely used as it satisfies the requirements and is suitable in other respects as well.

However, the capabilities required of civil engineering and construction machinery have gradually become more demanding, and the conditions under which cutting edges are used have also become more demanding, and conventional materials are no longer able to withstand use.

For example, in a bulldozer, an example of the temperature distribution at the lipper point (a type of cutting edge) when excavating hard rock is shown in FIG. When such usage conditions (high temperatures) are repeated, conventional Ni-Cr-Mo based low alloy steel suffers a significant decrease in hardness and progress of wear, as shown by the dotted line in Figure 3 (conventional steel G). It becomes so intense that it becomes unbearable to use. In other words, in addition to the above-mentioned mechanical properties, recent conditions that these cutting edges should have include wear resistance, which is 1.
It is required that the amount of wear during continuous excavation for hours is 700 ta or less.

These are summarized in Table 1. Table 1 (Note 1) Hardness obtained through tempering treatment of 60,000 or more.

(Note 2) Amount of wear when hard rock with an elastic velocity of 350/sec or more is continuously excavated for lhr.

Therefore, materials that take this point into consideration include SKD61, which has more alloying elements, and Cr-Mo or Cr-Mo materials.
-V-based medium alloy steels, or steels with higher carbon content and increased hardness, have come to be used.

However, although these steels can ensure wear resistance at high temperatures compared to conventional low-alloy steels, they are inferior in hot workability due to the increased amount of alloy, and increase the number of machining steps when machining the cutting edge by hot forging. It has a drawback.

The present invention was made in view of the above, and is a steel that has extremely good wear resistance at high temperatures, high ballability, and also has good hot workability. At CO. More than 35% to 0.50%, Sio. 50-1.0
Less than 0%, Mno. 80-1.50%, Cro. 35~
less than 1.00%, Moo. 50-1.50%, VO. 2
This is a steel for excavating cutting edges of magnolia construction machines, which has excellent hot workability and is characterized by containing 5 to 1.00% residual Ge and unavoidable impurities.

In other words, the steel of the present invention has bran softening resistance by increasing Mo compared to conventional steel, wear resistance by adding an appropriate amount of V, and further contains C, Si, Mn, and Cr.
, Mo, and V are blended in a well-balanced manner to minimize deterioration in hot workability.

Next, the reasons for limiting the individual components of the steel of the present invention will be described.

C: 0.35% to ensure hardness and hardenability
In addition, the amount must be 0.50% or less in order to suppress deterioration of toughness and hot workability.

The influence of each element on hot workability was confirmed using a hot shaking test method, and the evaluation was based on the number of times the test piece broke.

It is said that the smaller the number of times of rubbing in such a test, the worse the forgeability. Figure 4 shows the influence of the amount of C on the number of maneuvers, and as the amount of C increases, the number of hits decreases. In addition, the components of the test piece in this case are 0.8%Si-0.8%
Mn-0.9%Cf. Si...Si is solid dissolved in the base material and is effective in increasing the strength of the base material and resisting temper softening. However, if it is less than 0.5%, it is not effective, and in order to suppress the deterioration of hot workability, 1. It was set to less than .0%. FIG. 5 shows the influence of Si on the number of hot exchanges. The components of the test piece in this case are 0.45%C, 1.0%Mn, 0.5%C
r, 0.5% Mo. From this, it can be seen that as the Si content increases, the number of hot rubbings decreases. Mh...
Mn contributes to improving hardenability and hot workability, but 1
．． Even if it exceeds 5%, there is no significant effect on improving the dawn penetration property, and 0.
If it is less than 8%, the effect of improving hot workability will be slight.

FIG. 6 shows the influence of Nh on the number of hot operations. The components of the test piece in this case are 0.40%C-0.5%Si-1
．． It is 0% Cr.

This shows that 0.8% Mn or more is effective in increasing the number of hot shakes. Therefore, Mm' is limited to 0.8 to 1.5%. Cr... Cr: 0.50% is insufficient to ensure competitiveness and resistance to morning softening, and if it exceeds 1.00%, hot workability decreases. At the same time, material cutting and safe gas cutting become difficult. FIG. 7 shows the influence of Cr on the number of hot exchanges. The components of the test piece in this case are 0.4%C-0.8%Si-0.8%Mn
It is. From this, as Cr increases, high temperature (125
It can be seen that the number of hot tears at 0°C) decreases. Table 2 shows a comparison of the gas cutting properties of the same specimens. Table 2 It is generally said that gas cutting becomes difficult as the amount of Cr increases, but the test results in Table 2 also show that Cr at 1.0%
It can be seen that the gas cutting performance deteriorates when the temperature exceeds this value.

Therefore, Cr was limited to 0.5% to less than 1.0%. Mo
...Mo has a remarkable effect on improving hardenability and increasing resistance to competitive softening, and is also effective in improving grain quality.

In order to ensure these effects, less than 0.50% is insufficient, and if it exceeds 1.5%, the effect of competitive softening resistance is saturated, the rutting property is also reduced, and further, the important point of the present invention is One of the items, hot workability, deteriorates significantly. In Figure 8,
The influence of Mo on the number of hot shaking is shown.

The composition of the test piece in this case is 0.40%C-0.75%S
i-1.0%Mn-0.6%Cr. From now on Mo
It can be seen that as the number of hot shakes increases, the number of hot shakes decreases. Therefore, Mo is limited to 0.5 to 1.5%. V...
V is effective in increasing resistance to softening, preventing grain coarsening, and improving wear resistance, but if it is less than 0.25%, no such effect can be expected, and if it exceeds 1.0%, hot workability This results in a decrease in hardness, machinability, grindability, and toughness. FIG. 9 shows the influence of V on the number of hot shakes. In this case T. P. Composition is 0.4%C-0.9%Si-0.8
%Mn. From this, it can be seen that as the V amount increases, the number of times of hot bonding decreases.

Therefore, V is limited to 0.25 to 1.0%. The limited ranges of various elements have been described above, but in order to fully demonstrate the good hot workability, which is an important item of the present invention,
Although i, Mh, Cr, Mo, and V need to be blended in a well-balanced manner, it is difficult to quantitatively understand their effects.

In the present invention, in order to find and find a well-balanced composition, experiments were conducted on numerous types of component steel to determine the component range. Table 3 shows some of them. FIG. 10 shows the results of high-temperature switching tests performed on the steels shown in Table 3. As can be seen from Table 3 and Figure 10, experimental steel 7 has the highest number of hot soaking cycles and has good workability over a wide range of working test temperatures of 1000 to 1250 pm, that is, it is easy to handle during hot working. I understand that there is something.

Therefore, the steel of the present invention is based on Experimental Steel 7, and the range of each component is determined as described above. As described above, in the present invention, we have studied the effects of individual elements on hot workability, and also their interactions, to achieve good hot workability and a wide range of processable temperatures. We have developed a steel for drilling cutting edges with the following characteristics.

Next, experimental examples using the steel of the present invention will be described.

Table 4 shows composition examples, main mechanical properties, hot workability (torsion test), and wear weight due to rock excavation of the steel of the present invention and the conventional steel. The amount of wear caused by rock excavation in Table 4 is the result of manufacturing a ripper point as shown in FIG. 1 and performing excavation work with a pulldozer in hard rock where the elastic wave velocity is 3500/sec or more.

Furthermore, FIG. 3 shows the oven softening resistance of the invention steel and comparative steel.
As can be seen from Table 4, the steel of the present invention has much better wear resistance than the conventional low-alloy steel (G), and also has SKD61
It can be seen that it has wear resistance equal to or higher than that of (H), improved steels (1), and (J), and satisfies the requirements in Table 1. This can be supported by the fact that, as shown in FIG. 3, the late-night reversion softening resistance of the steel of the present invention is significantly superior to that of conventional steels (G), (H), and (1).

The steel of the present invention is also superior to the conventional steel (G) in terms of ballability expressed by impact value. Next, hot workability was compared using a hot grip test.

As mentioned above, the quality of hot workability is determined by the wide temperature range of the number of bumps and high number of laps at the processing temperature. Table 5 shows the number of hot exchanges at 1000° C. and 1200 qo, thereby comparing the number of cycles at both high and low temperatures. The steel of the present invention shows a number of hot rubbings of 24 to 28 times at both high and low temperatures, which is close to 31 times of the conventional steel (G), and compared to the conventional improved steels (1), (J) and SKD61 (H).
It can be seen that the workability is much better than that of 19 to 24 times, and that good workability is maintained even at low temperatures. Furthermore, in the actual forging of ripper points,
Table 6 shows the man-hours and punch life during forging for forming the mounting holes. Table 6, Figure 11 shows the actual forging pattern.

In the figure, 1' is the rough formed material of Ripper Point, and 3
is ponchidai.

The rough molded material is heated to about 1200° C., placed in a mold (not shown), and pressed with a punch die. As shown in Table 6, it can be seen that (H) steel and (1) steel, which have a low number of hot exchanges, require a high number of processing steps and have a short punch life even in actual forging. On the other hand, it can be seen that the steel of the present invention} has workability equivalent to that of the conventional steel (G). As described above, the steel of the present invention has extremely good wear resistance at high temperatures, excellent rutting resistance, can withstand severe excavation conditions, hot workability is almost the same as low alloy steel, and manufacturing cost is low. These characteristics make it ideal as a steel for excavating cutting edges of construction machinery.

[Brief explanation of the drawing]

Figure 1a is a perspective view of the ripper point and its shank;
Figure 1b is a perspective view of the ripper point removed from the shank, and Figure 2 is a diagram of the temperature distribution when the ripper point is in use.
Figures showing examples; Figure 3 is a diagram showing the relationship between the temperature and hardness of the steel of the present invention and comparative steel; Figures 4, 5, 6, 7, 8 and 8; Figure 9 shows C, Si, Mn, Cr, Mo,
Diagram showing the relationship between the elemental content of V and hot manipulation Islam, No. 10
The figure is a diagram showing the relationship between the temperature and the number of simulations in a hot shaking test of various component steels (experimental steels), and Figure IY is a perspective view showing a forging pattern for forming a hole for attaching a ripper point. 1... Ripper point, 1'... Ripper point composition shape, 2... Ripper shank, 3"""
Punch die. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11

Claims (1)

[Claims] 1% by weight: C more than 0.35% to 0.50% Si 0.50 to less than 1.00% Mn 0.80 to 1.50% Cr 0.35 to less than 1.00% A steel for excavating cutting edges of construction machines with excellent hot workability, characterized by comprising Mo 0.55-1.50% V 0.25-1.00% with the remainder being Fe and unavoidable impurities.