CN1100156C

CN1100156C - New brake hub material

Info

Publication number: CN1100156C
Application number: CN99101407A
Authority: CN
Inventors: 姜启川; 赵玉谦; 赵宇光; 刘长锁; 金胜灿; 张瑞卿; 王化平; 王金国; 关庆丰; 王树奇; 方建儒; 战松江
Original assignee: Jilin University of Technology
Current assignee: Jilin University of Technology
Priority date: 1999-01-25
Filing date: 1999-01-25
Publication date: 2003-01-29
Anticipated expiration: 2019-01-25
Also published as: CN1232882A

Abstract

The present invention relates to a braking hub material, particularly to a cast iron braking hub material used for a heavy duty load-carrying vehicle which can carry goods of more than 9 tons. The present invention changes a traditional concept that a main mode of the ineffectiveness of a braking hub is always considered as abrasion and discovers that a main mode of the ineffectiveness of a braking hub is cracking caused by hot and cold exhaustion. Therefore, pearlite matrix gray cast iron is replaced by ferrite matrix magnesium iron or vermicular iron to manufacture the braking hub so as to make the braking hub has the advantages of high toughness, obviously enhanced hot and cold exhaustion property resistance, obviously prolonged service life, etc.

Description

Brake hub material

The invention belongs to the high life brake hub material.

Brake hubs is one of key security personnel part of automobile.Traditional idea thinks that the inefficacy of brake hubs is wearing and tearing, and therefore, the brake hubs of cargo truck all adopts the casting of pearlite matrix graphitic cast iron to form at present.Bogie below 9 tons adopts HT200, and (content of pearlite in alloy＞90%, graphite are the A type.) cast; (content of pearlite in alloy＞90%, graphite are A type (flake graphite that has wedge angle) to traction engine employing HT250 more than 9 tons.) cast (also not choosing suitable material at present).But the performance of HT250 can not satisfy the requirement of heavy duty vehicle brake hubs more than 9 tons far away at present, and the key issue of existence is that cold-and-heat resistent fatigue property and the obdurability of HT250 is poor.The inefficacy of heavy duty vehicle brake hubs mainly is the early stage cold and hot fatigue cracking (be full of cracks) that occurs in brake hubs surface more than 9 tons, and crack propagation is very fast then, causes ftractureing, and loses the brake ability and loses efficacy.Run the more heavy goods vehicles more than 9 tons in hill path at present when 20000 kilometers left and right sides of operation, just (life-span of normal braking hub should be more than 100000 kilometers because of the fatigue cracking cracking loses efficacy for brake hubs.), seriously threaten the safety of people and car, reduce quality product and prestige and limited the development of heavy duty vehicle.Because the work-ing life of brake hubs is low, cause very big financial loss simultaneously.The inventor finds that by to a large amount of heavy duty vehicle brake hubs analysis of failure mechanism wearing and tearing are the secondary causes that lost efficacy, and main failure forms is a fatigue cracking.Therefore, by changing the matrix and the graphite form of brake hubs, improve its cold-and-heat resistent fatigue capability, prevent to lose efficacy because of fatigue cracking causes the brake hubs cracking, be to improve more than 9 tons heavy goods vehicles work-ing life, quality product and prestige and promote one of key issue of its development, this also is that the present invention innovates part.

The objective of the invention is to change the traditional concept that heavy goods vehicles brake hubs failure cause more than 9 tons is mainly wearing and tearing, by changing the chemical ingredients of cast iron brake hubs, with now the pearlite matrix and the A type graphite of the cast iron brake hubs of 9 tons of heavy duty vehicles uses are changed into obdurability, cold-and-heat resistent fatigue property (germinating and the FATIGUE CRACK GROWTH speed that reduces to have germinated of minimizing surface heat fatigue cracking that ferrite matrix and sphere or quasiflake graphite improve heavy duty vehicle brake hubs more than 9 tons.) and work-ing life.

The object of the present invention is achieved like this: heavy duty vehicle now makes the cylinder iron chemical ingredients of brake hubs more than 9 tons by changing, and makes the pearlite matrix and the A type graphite of the cast iron brake hubs of existing use change into obdurability, cold-and-heat resistent fatigability and the work-ing life that ferrite matrix and globular graphite or quasiflake graphite improve the car brake hubs.

Obdurability, cold-and-heat resistent fatigability and the technical scheme in work-ing life that the present invention improves heavy duty vehicle brake hub material more than 9 tons comprise two aspects.First aspect is to change pearlite matrix into ferrite matrix, improve toughness, liptinite and the thermal conductivity of matrix, reduce the thermal stresses and the transformation stress that produce in the rapid heat cycle process, because of ferritic transformation temperature is higher than pearlitic transformation temperature far away, therefore, the transformation stress that ferrite produces in the rapid heat cycle process is less than ball light body, and ferritic toughness also is higher than the toughness of ball light body far away simultaneously; Second aspect is to change A type graphite into spherical graphite or quasiflake graphite, compares with A type graphite because of sphere or quasiflake graphite to be difficult for producing stress concentration, and the effect of isolating of matrix is far smaller than A type graphite.Therefore, tensile strength, yield strength, toughness and the plasticity of ferrite matrix ductile cast iron or ferrite matrix vermicular cast iron all is higher than HT250 far away (either pearlite occurred＞90%, graphite is the A type.)。

In the rapid heat cycle process of brake, the ferrite matrix magnesium iron or the iron of wriggling are compared with HT250, transformation stress and thermal stresses are little, ferrite matrix has high toughness simultaneously, add graphite and be sphere or vermiform and compare with A type graphite that to isolate matrix poor, make matrix obdurability height, and be difficult for as formation of crack, cause crackle to be difficult for germinating, it is the expansion of sphere or the unfavorable crackle of vermiform that the while ferrite matrix magnesium iron or the iron of wriggling have high obdurability and graphite form, therefore, even in case crack initiation also is difficult for expansion.And the cold and hot fatigue cracking with HT250 of pearlite matrix and A type graphite easily germinates, and in case germinating, propagation rate is very fast, because of A type graphite is the sheet that has wedge angle, it is serious to isolate matrix, easily as formation of crack, and pearlitic toughness and thermostability all are lower than ferrite, therefore, repeatedly, repeatedly, under the comprehensive action of the transformation stress of alternation, thermal stresses, mechanical stress, in case flake graphite links to each other with flake graphite, it is crack initiation, and crack growth rate is very fast in this way, causes MATRIX CRACKING very soon, and brake hubs lost efficacy.

Therefore, the ferrite matrix magnesium iron of the present invention or the iron brake hubs of wriggling have the ability of cold and hot fatigue crack initiation of very strong opposing and expansion in the chilling chilling thermal process of brake, is greatly enhanced its work-ing life.

The chemical ingredients (wt%) of cast ferrite matrix ductile cast iron brake hubs of the present invention: C:3.5～4.0; Si:2.4～3.0; Mn＜0.5; P＜0.06; S＜0.03; Mg:0.03～0.05; RE:0.02～0.04.Performance: σ _b＞400MPa, δ＞10%, HB＜180.Metallographic structure: ferrite content＞75%, nodularization rate: 1～4 grade (national standard), carbide amount＜3%, iron phosphide eutectic＜3%.

The chemical ingredients (wt%) of cast ferrite matrix vermicular cast iron brake hubs of the present invention: C:3.5～3.9; Si:2.4～3.0; Mn＜0.5; P＜0.06; S＜0.03; Mg:0.01～0.03; RE:0.04～0.07; Ti＜0.2.Performance: σ _b＞350MPa, δ＞2%, HB＜180.Metallographic structure: ferrite content＞75%, nodulizing rate:＞55%, carbide amount＜3%, iron phosphide eutectic＜3%.

The as-cast ferrite ductile iron of the present invention or the iron brake hubs of wriggling are compared with HT200 or the HT250 brake hubs used at present, the former tensile strength, unit elongation, cold-and-heat resistent fatigue property etc. are better than the latter greatly, tensile strength improves more than 70%～100%, the cold-and-heat resistent fatigue property increases exponentially, and service testing has also confirmed above-mentioned experimental result well.

The present invention casts brake hubs with casting ferrite with nodular cast iron and vermicular cast iron, and its composition, tissue, performance and cold and hot fatigue property are provided by table 1,2,3 listed embodiment.Find out the σ of casting ferrite with nodular cast iron and vermicular cast iron by table 1,2,3 _b(tensile strength), δ (unit elongation), thermal fatigue resistance all are better than HT250.

Table 1 ferrite matrix magnesium iron composition, microstructure and property

Table 2 cast ferrite matrix wriggle ferrous components, microstructure and property

The cold and hot fatigue experiment result of table 3

At First Auto Group automotive research institute preventing test point---Nong An brew-house truck organization carries out entrucking and sport car experiment.

(pearlite matrix, graphite are the A type to adopt HT250.) brake hubs of casting is contained in and runs on 9 tons of more heavy-duty trucks of hill path, when move 20000 kilometers left and right sides, just because of fatigue cracking splits, brake hubs ftractures, and causes the brake hubs inefficacy.Same chassis refills the brake hubs of a cover HT250 casting, and the result is the same with first cover, and when running to 20000 kilometers left and right sides equally, because of fatigue cracking splits, brake hubs ftractures and lost efficacy.

The present invention adopts C:3.81; Si:2.72; Mn:0.42; P:0.051; S:0.022; Mg:0.041; The ferrite matrix ductile cast iron of RE:0.022 (wt%) has been cast 9 tons of heavy duty vehicle brake hubs.Its metallographic structure: ferrite content＞90%, the nodularization rate: 1 grade, carbide amount＜1%, iron phosphide eutectic＜1%. Performance: σ _b: 460MPa, δ: 16.1%, HB:166.This brake hubs is contained on the same chassis (it is more to run the hill path), has moved about 30000 kilometers during to the application patent of invention, but has pulled down observation, does not also have discovery check surface to occur, and all are normal, loading operation again, and predicted life improves greatly than HT250.

The present invention adopts C:3.73; Si:2.83; Mn:0.45; P:0.052; S:0.021; Mg:0.013; RE:0.051; The ferrite matrix vermicular cast iron of Ti:0.011 (wt%) has been cast 9 tons of heavy duty vehicle brake hubs.Its metallographic structure: ferrite content＞90%, nodulizing rate 70%, carbide amount＜1%, iron phosphide eutectic＜1%. Performance: σ _b: 380MPa, δ: 3.5%, HB:168.This brake hubs is contained on another 9 tons of heavy-duty trucks, during to the application patent of invention, has moved about 30000 kilometers, the be full of cracks of discovery, and all are normal.

Claims

1, brake hub material is characterized in that:

A, employing cast ferrite matrix ductile cast iron, its chemical ingredients (wt.%): C:3.5-4.0, Si:2.4-3.0, Mn＜0.5, P:＜0.06, S＜0.03, Mg:0.03-0.05, RE:0.02-0.04; Metallographic structure: ferrite content＞75%, 1～4 grade of nodularization rate, carbide amount＜3%, iron phosphide eutectic＜3%;

B, employing cast ferrite matrix vermicular cast iron, its chemical ingredients (Wt.%): C:3.5-3.9, Si:2.4-3.0, Mn＜0.5, P＜0.06, S＜0.03, Mg:0.01-0.03, RE:0.04-0.07, Ti＜0.2; Metallographic structure: ferrite content＞75%, nodulizing rate＞55%, carbide amount＜3%, iron phosphide eutectic＜3%.