JPH0772320B2 - Abrasion resistant Fe-base casting alloy for rocker arms having high strength and toughness - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has a high strength and a high toughness and is excellent in wear resistance, and is particularly suitable for use as a rocker arm of an internal combustion engine. It is about.

[Conventional technology]

Conventionally, a large number of wear-resistant Fe-based casting alloys have been generally used for manufacturing a rocker arm of an internal combustion engine.

[Problems to be solved by the invention]

However, with the recent increase in output and weight of engines, it has become necessary for the rocker arm to be smaller and thinner, but conventional wear-resistant Fe-based casting alloys are all excellent in durability. Although it exhibits wear resistance, it is the current situation that it is not possible to satisfy these requirements sufficiently due to insufficient strength and toughness.

[Means for solving problems]

Therefore, the present inventors, from the above viewpoints, as a result of conducting research to develop a loker arm Fe-based casting alloy having high strength and high toughness and also excellent in wear resistance, % (Hereinafter,% means weight%), C: 2.5-4%, Cr: 20-40%, Mo: 0.01-1%, Si: 1-4%, Mn: 0.1-1%, Co: 0.1 -1%, W: 0.05-1%, Ta: 0.01-1%, Ti: 0.01-1%, Al: 0.01-0.1%, Hf: 0.001-0.1%, Ni: 1-5%, Fe-based casting alloys with the balance consisting of Fe and unavoidable impurities have all of the above characteristics, enable downsizing and thinning of the rocker arm, and are also excellent for practical use under severe conditions. We have obtained the knowledge that it exhibits excellent performance.

The present invention has been made based on the above findings, and the reason why the component composition is limited as described above will be described below.

(A) CC The C component has a function of improving the strength by forming a solid solution in a part of the base material, forming carbides, improving wear resistance, and further improving castability. If the content is less than 2.5%, the desired effect cannot be obtained, while if the content exceeds 4%, the toughness of the alloy decreases, so the content was defined as 2.5-4%. .

(B) Cr The Cr component has the function of forming carbides and significantly improving the wear resistance of the alloy, but if the content of Cr is less than 20%, the desired excellent wear resistance cannot be ensured. On the other hand, if the content exceeds 40%, the toughness of the alloy is significantly deteriorated, so the content was set to 20-40%.

(C) Mo Mo component has the action of forming carbides to improve wear resistance and to form a solid solution with the base material to improve alloy strength.
If the content is less than 0.01%, the desired effect cannot be obtained, while if the content exceeds 1%, the effect is saturated and no further improvement effect appears, resulting in economical efficiency. In consideration of the above, the content is set to 0.01 to 1%.

(D) Si The Si component has the effect of improving the castability deterioration due to the high content of Cr, but if the content is less than 1%, the desired effect cannot be obtained for the above-mentioned action, while the content thereof is If the content exceeds 4%, the toughness will decrease, so the content was defined as 1 to 4%.

(E) Mn The Mn component has the function of improving the toughness of the alloy, but if the content is less than 0.1%, the desired toughness improving effect cannot be obtained, while if the content exceeds 1%, the resistance is increased. Since the wear resistance is lowered, the content is set to 0.1 to 1%.

(F) Co The Co component has the action of forming a solid solution in the matrix to improve the strength of the alloy, but if its content is less than 0.1%, the desired strength-improving effect cannot be obtained, while its content is 1 Even if it exceeds%, no further improvement effect can be obtained, and the content thereof is set to 0.1 to 1% in consideration of economical efficiency.

(G) The WW component has a strength-improving action due to solid solution of the base material and an abrasion resistance-improving action due to formation of carbide,
If it is less than 0.05%, the desired effect cannot be obtained, while if it exceeds 1%, the toughness of the alloy deteriorates. Therefore, the content is set to 0.05 to 1%.

(H) Ta The Ta component, like W, has an effect of improving strength by solid solution of the base material,
In addition, there is an effect of improving wear resistance due to the formation of carbides, but if the content is less than 0.01%, the desired effect is not obtained, while if the content exceeds 1%, a further improving effect appears. First, considering the economic efficiency, the content of 0.01
It was set at ~ 1%.

(I) Ti and Al Ti and Al components contribute to the refinement of the structure in the coexisting state and have the effect of significantly improving the alloy strength, but their contents are Ti: less than 0.01%, Al: If the content is less than 0.01%, the desired strength-improving effect cannot be obtained. On the other hand, if the content of Ti exceeds 1% and that of Al exceeds 0.1%, the toughness of the alloy decreases. , Its content is T
i: 0.01-1%, Al: 0.01-0.1%.

(J) Hf The Hf component has a function of forming a solid solution in the base material to further improve the strength and toughness of the alloy, but if the content is less than 0.001%, the desired improving effect on the above function cannot be obtained. 0.1
%, The above effect will be saturated and the further improvement effect will not be obtained.
It was set to 0.001 to 0.1%.

(K) Ni Ni component acts as a solid solution in the matrix to further improve the toughness of the alloy, but if the content is less than 1%, the desired high toughness cannot be ensured, and one of the contents If the amount exceeds 5%, the wear resistance will decrease, so the content was defined as 1 to 5%.

〔Example〕

Next, the Fe-based casting alloy of the present invention will be specifically described by way of examples.

Using an ordinary high-frequency melting furnace, an Fe-based alloy melt having the composition shown in Table 1 was prepared.
A Fe-based alloy melt was cast into a rocker arm by the usual Lost wax method, and subsequently kept in the atmosphere at a predetermined temperature within a range of 800 to 950 ° C for 1 hour, followed by a quenching treatment of oil quenching, and also in the atmosphere, 100 to 550 The rocker arms of the Fe-based cast alloys 1 to 25 of the present invention and the comparative Fe-based cast alloys 1 to 19 were manufactured by holding at a predetermined temperature in the range of ° C for 2 hours and then allowing them to cool.

The comparative Fe-based cast alloys 1 to 19 have compositions in which any one of the constituent components (marked with * in Table 1) is out of the range of the present invention.

Next, with respect to various Fe-based casting alloy-made rocker arms obtained as a result of this, tensile strength for the purpose of evaluating strength, Sharpy impact value was measured for the purpose of evaluating toughness, and for the purpose of further evaluating wear resistance. In addition to measuring the Rockwell hardness (C scale), incorporating this into a 4-cylinder OHC engine, engine speed: 850 rpm, oil: LPG waste oil (oil temperature: 80 ° C), material of the cam that is the counterpart: FC25 A chill material was run for 400 hours, and an actual wear test was performed to measure the maximum wear depth of the rocker arm and cam. The results of these measurements are shown in Table 2.

〔The invention's effect〕

From the results shown in Table 2, the present invention Fe-based casting alloys 1 to 25
Both have high strength and high toughness, and show excellent wear resistance in a state of low opponent attack, whereas
As seen in Comparative Fe-based casting alloys 1 to 19, if the content of any one of the constituents deviates from the scope of the present invention, at least one of the above properties becomes inferior. Is clear.

As described above, since the Fe-based cast alloy of the present invention has high strength and high toughness, it enables downsizing and thinning of the rocker arm, and also has low opponent attack and excellent wear resistance. When it is used as a rocker arm, it has industrially useful properties such that it exhibits excellent performance over a remarkably long period of time.

Claims (1)

[Claims] 1. C: 2.5-4%, Cr: 20-40%, Mo: 0.01-1%, Si: 1-4%, Mn: 0.1-1%, Co: 0.1-1%, W: 0.05 ~ 1%, Ta: 0.01 ~ 1%, Ti: 0.01 ~ 1%, Al: 0.01 ~ 0.1%, Hf: 0.001 ~ 0.1%, Ni: 1 ~ 5%, and the rest from Fe and inevitable impurities. A high-strength and high-toughness wear-resistant Fe-based casting alloy for rocker arms, which has the following composition (above wt%).