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合金鋼
在普通碳素鋼基礎(chǔ)上添加適量的一種或多種合金元素而構(gòu)成的鐵碳合金。根據(jù)添加元素的不同,并采取適當(dāng)?shù)募庸すに?,可獲得高強(qiáng)度、高韌性、耐磨、耐腐蝕、耐低溫、耐高溫、無磁性等特殊性能。
合金鋼的主要合金元素有硅、錳、鉻、鎳、鉬、鎢、釩、鈦、鈮、鋯、鈷、鋁、銅、硼、稀土等。其中釩、鈦、鈮、鋯等在鋼中是強(qiáng)碳化物形成元素,只要有足夠的碳,在適當(dāng)條件下,就能形成各自的碳化物,當(dāng)缺碳或在高溫條件下,則以原子狀態(tài)進(jìn)入固溶體中;錳、鉻、鎢、鉬為碳化物形成元素,其中一部分以原子狀態(tài)進(jìn)入固溶體中,另一部分形成置換式合金滲碳體;鋁、銅、鎳、鈷、硅等是不形成碳化物元素,一般以原子狀態(tài)存在于固溶體中。
合金鋼種類很多,通常按合金元素含量多少分為低合金鋼(含量<5%),中合金鋼(含量5%~10%),高合金鋼(含量>10%);按質(zhì)量分為優(yōu)質(zhì)合金鋼、特質(zhì)合金鋼;按特性和用途又分為合金結(jié)構(gòu)鋼、不銹鋼、耐酸鋼、耐磨鋼、耐熱鋼、合金工具鋼、滾動軸承鋼、合金彈簧鋼和特殊性能鋼(如軟磁鋼、永磁鋼、無磁鋼)等。
在鋼中除含鐵、碳和少量不可避免的硅、錳、磷、硫元素以外,還含有一定量的合金元素,鋼中的合金元素有硅、錳、鉬、鎳、硌、礬、鈦、鈮、硼、鉛、稀土等其中的一種或幾種,這種鋼叫合金鋼 各的合金鋼系統(tǒng),隨各自的資源情況、生產(chǎn)和使用條件不同而不同,國外以往曾發(fā)展鎳、硌鋼系統(tǒng),我國則發(fā)現(xiàn)以硅、錳、釩、鈦、鈮、硼、鉛、稀土為主的合金鋼系統(tǒng) 合金鋼在鋼的總產(chǎn)量中約占百分之十幾,一般是在電爐中冶煉的按用途可以把合金鋼分為8大類,它們是:合金結(jié)構(gòu)鋼、彈簧鋼、軸承鋼、合金工具鋼、高速工具鋼、不銹鋼、耐熱不起皮鋼,電工用硅鋼。
合金工具鋼
合金工具鋼具有更高硬度、耐磨性,更好的淬透性、熱硬性和回火穩(wěn)定性等。因而可以制造模具、量具和其它工具。
1、低合金工具鋼
低合金工具鋼是在碳素工具鋼的基礎(chǔ)上,加入少量的合金元素Cr、Mn、Si、W、V等 ,提高鋼的淬透性和回火穩(wěn)定性,因而提高鋼的強(qiáng)度、耐磨性和熱硬性。在230 ~260℃回火后硬度仍保持HRC60以上,從而保證一定的熱硬性。常用的低合金工具鋼有9SiCr、CrWMn等。
低合金工具鋼的熱處理為球化退火、淬火和低溫回火。最后組織為回火馬氏體、合金碳化物和少量殘余奧氏體。
2、高速鋼
高速鋼是一種高碳合金工具鋼,用高速鋼制的刀具,可以進(jìn)行高速切削,具有良好的熱硬性。當(dāng)切削溫度高達(dá)600℃左右時(shí)硬度仍無明顯下降。
高速鋼中含有大量的合金元素W、Mo、Cr、V等,使鋼具有高的硬度和耐磨性,較高的熱硬性,足夠的強(qiáng)度和韌性等。這些性能當(dāng)然也要通過適當(dāng)?shù)臒崽幚聿拍鼙WC。
高速鋼的鑄態(tài)組織中有粗大的魚骨狀合金碳化物,使鋼的機(jī)械性能降低,但不能用熱處理來消除,只有采用反復(fù)鍛擊的辦法將其擊碎,并均勻分布在基體上。高速鋼鍛造之后,要進(jìn)行退火,以消除應(yīng)力,降低硬度,為以后的淬火作組織上的準(zhǔn)備。
高速鋼只有通過正確的淬火和回火才能使性能充分發(fā)揮出來。W18Cr4V鋼的最終熱處理工藝曲線如圖所示。淬火溫度較高的目的是使大量的合金碳化物溶入奧氏體中,以得到良好的紅硬性。高速鋼淬火后,還保留一部分殘余奧氏體,一次回火難以全部消除,影響鋼的硬度和耐磨性,故必須經(jīng)多次回火使其全部轉(zhuǎn)變,一般常采用560℃三次回火,每次保溫1小時(shí)。
3、硬質(zhì)合金
硬質(zhì)合金是將特制的高熔點(diǎn)、高硬度的金屬碳化物粉末和粘結(jié)劑混合,壓制成型,再經(jīng)燒結(jié)而成的一種粉末冶金材料。
硬質(zhì)合金的性能特點(diǎn)是:硬度高HRA(86~93),相當(dāng)于HRC(69~81)。熱硬性好(可達(dá)900℃~1100℃),耐磨性優(yōu)良。因此硬質(zhì)合金主要用做切削工具。其刀具的切削速度比高速鋼可提高4~7倍,壽命提高5~80倍,制造模具、量具壽命可提高20~150倍。有的金屬材料如奧氏體耐熱鋼和不銹鋼等用高速鋼無法切削加工,若用含WC的硬質(zhì)合金就可以切削加工。
合金模具鋼
用于制作冷、熱模具的鋼種為模具鋼
1.冷模具鋼
包括冷鐓模、拉絲模、滾絲模等,屬于接近室溫狀態(tài)下對金屬進(jìn)行變形加工的一種模具。要求有高的硬度和良好的耐磨性,以及足夠的強(qiáng)度和韌性,熱處理變形要小。小模具用CrWMn來制造,大型模具采用淬透性高、抗磨性高的Cr12鋼來制造。
這類鋼熱處理過程是球化退火,淬火,低溫回火?;鼗鸷蠼M織是回火馬氏體,合金碳化物和少量的殘余奧氏體。
2.熱模具鋼
在高溫下工作的模具鋼如熱鍛模。要求在高溫下有高的強(qiáng)度及足夠的耐磨性和韌性,良好的抗熱疲勞性,為使整體性能一致,還需有良好的淬透性。
合金量具鋼
合金量具鋼用于制造各種測量工具,如千分尺、量規(guī)、塊規(guī)等。
常用量具
為了保證量具的精確度,制造量具的鋼應(yīng)具有良好的尺寸穩(wěn)定性、較高的硬度及耐磨性。
量具鋼沒有專用鋼。尺寸小、形狀簡單、精度較低的量具,用高碳鋼制造;復(fù)雜的精密量具用低合金刃具鋼制造。
alloy steel
In the ordinary carbon steel on the basis of adding some one or more alloying elements which constitute the iron-carbon alloy. According to the different elements added, and take appropriate processing technology.Will be high-intensity, high toughness, wear resistance, corrosion resistance, low temperature resistance, high temperature, non-magnetic, and other special properties.
Steel is the main alloying elements silicon, manganese, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, aluminum, copper, boron, such as rare earth. Including vanadium, titanium, niobium, zirconium, such as in steel is strong carbide forming elements. As long as there is sufficient carbon, under appropriate conditions, will be able to form their own carbide; When carbon or missing in the high-temperature conditions, while atomic enter solid solution. Manganese, chromium, tungsten, molybdenum carbide formation of the elements. Atomic part of the state to enter solid solution, another part of a replacement alloy cementite; Aluminum, copper, nickel, cobalt, silicon carbide forming elements is not, to the general state of atoms in solid solution in existence.
There are many kinds of steel, normally divided into the number of alloy elements in low alloy steel (content <5%).In steel (in 5% to 10%),high-alloy steel (content> 10%);By mass into high-quality steel, alloy steel qualities; According to characteristics and uses are divided into alloy structural steel, stainless steel, acid-proof steel, wear-resistant steel, heat-resistant steel, alloy tool steel, rolling bearing steel, spring steel and special alloy steel performance (such as soft magnets, permanent magnet steel, non-magnetic Steel).
In steel, in addition to iron, carbon and a small amount of the inevitable silicon, manganese, phosphorus, sulfur, also contain a certain amount of alloying elements. Alloy elements in steel with silicon, manganese, molybdenum, nickel, Ge, alumina, titanium, niobium, boron, lead, rare earth, and so one or several of them,Steel is the steel that the steel system.With their resources, the production and use of different conditions and different. Foreign previous development nickel, steel Ge system, China was found to silicon, manganese, vanadium, titanium, niobium, boron, lead, rare earth-based steel alloy steel in the steel system in the total output of about 10 per cent. Generally in the smelting furnace by the use of the steel can be divided into eight major categories.They are: alloy structural steel, spring steel, bearing steel, alloy tool steel, high speed tool steel, stainless steel, heat-resistant skin can not afford steel, silicon steel electrician.
Alloy tool steel
The alloy tool steel has a higher degree of hardness, the resistance to wear, better hardenability, hot rigidity and tempering stable and so on. Thus may make the mold, the measuring instrument and other tools.
1st, low-alloy tool steel
The low-alloy tool steel is in the ordinary tool steel foundation, joins few alloying element Cr, Mn, Si, W, V and so on, enhances the steel the hardenability and the tempering stability, thus enhances the steel the intensity, the resistance to wear and the hot rigidity. Degree of hardness still maintained above HRC60 after 230 ~ 260 ℃ tempering, thus guaranteed the certain hot rigidity. The commonly used low-alloy tool steel has 9SiCr, CrWMn and so on.
Low-alloy tool steel heat treatment for , quenching and low tempering. Finally organizes for the tempered martensite, the alloy carbide and the few remaining austenite.
2nd, high-speed steel
The high-speed steel is one kind of high carbon alloy tool steel, with the high-speed steel system cutting tool, may carry on the high-speed cutting, has the good hot rigidity. When the cutting temperature reached as high as 600 ℃ about degree of hardness still not obviously to drop.
In the high-speed steel includes massive alloying element W, Mo, Cr, V and so on, enable the steel to have the high degree of hardness and the resistance to wear, higher hot rigidity, enough intensity and tough and so on. These performance certainly also must be able to guarantee through the suitable heat treatment.
In the high-speed steel casting condition organization has the thick fish bones shape alloy carbide, causes the steel the machine capability to reduce, but cannot use the heat treatment to eliminate, only has the means which uses repeatedly hammers strikes it to crush, and evenly distributes in the substrate. After high-speed steel forging, must carry on , the stress-relieving, reduces degree of hardness, will be the later quenching makes in the organization the preparation.
The high-speed steel only through correct quenching and the tempering can enable the performance fully to display. The W18Cr4V steel final heat treatment craft curve like chart shows. A hardening temperature higher goal is causes the massive alloy carbide to dissolve into in the austenite, by obtains the good red hardness. After high-speed steel quenching, but also retains part of remaining austenite, a tempering completely eliminates with difficulty, affects the steel degree of hardness and the resistance to wear, therefore must pass through the multiple tempering to cause it completely to transform, generally often uses 560 ℃ three tempering, each time keeps warm for 1 hour.
3rd, hard alloy
The hard alloy is high mp, the high degree of hardness metal carbide powder and the cementing agent mix which specially makes, suppresses takes shape, again passes through one kind of powder metallurgy material which agglutinates becomes.
The hard alloy performance characteristic is: Degree of hardness high HRA (86 ~ 93), is equal to HRC (69 ~ 81). The hot rigidity good (may reach 900 ℃ ~ 1,100 ℃), the resistance to wear is fine. Therefore the hard alloy mainly with makes the cutting tool. Its cutting tool cutting speed may enhance 4 ~ 7 times compared to the high-speed steel, the life enhances 5 ~ 80 times, makes the mold, the measuring instrument life may enhance 20 ~ 150 times. Some metal material like austenite high-temperature steel and the stainless steel urgently need the high-speed steel to be unable the machining, if with contains WC the hard alloy to be allowed the machining.
Alloy molding tool steel
Uses in coldly to manufacture, the hot mold aluminum is the molding tool steel
1. Cold molding tool steel
Including Leng Duimu, the wiredrawing mold, roll the silk mold and so on, belongs approaches under the room temperature condition to carry on the distortion processing to the metal one kind of mold. The request has the high degree of hardness and the good resistance to wear, as well as the enough intensity and toughness, the heat treatment distorts must be small. The small mold makes with CrWMn, the large-scale mold uses the hardenability to be high, the abrasion resistant high Cr12 steel makes.
This kind of steel heat treatment process is quenching, low tempering. After the tempering the organization is the tempered martensite, the alloy carbide and the few remaining austenite.
2. Hot molding tool steel
The molding tool steel like hot forging die works which under the high temperature. The request has the high intensity and the enough resistance to wear and toughness under the high temperature, good resists heat weariness, for causes the overall performance to be consistent, but also must have the good hardenability.
Alloy measuring instrument steel
The alloy measuring instrument steel uses in to make each kind of measuring tool, like micrometer, gauge, slip gauge and so on.
Commonly used measuring instrument
In order to guarantee the measuring instrument the precision, makes the measuring instrument the steel to be supposed to have the good size stability, a higher degree of hardness and the resistance to wear. Measuring instrument steel not special-purpose steel. The size small, the shape is simple, a precision lower measuring instrument, makes with the high-carbon steel; The complex precision measuring instrument makes with the low-alloy Blades steel.