余熱正火(退火)

⑴得當(dāng)掌握鍛件進(jìn)爐前的溫度。當(dāng)零件溫度較高時(shí)需求對(duì)鍛件進(jìn)行吹風(fēng)冷卻，使零件溫度降低到所需求的正火溫度，同時(shí)熱處分爐功率需求有一定的充裕，開(kāi)始制造前和少量鍛件溫度低時(shí)進(jìn)行加熱。

⑵確定合理保溫時(shí)間。保溫時(shí)間過(guò)長(zhǎng)會(huì)會(huì)造成晶粒粗壯，保溫時(shí)間過(guò)短會(huì)造成構(gòu)造轉(zhuǎn)變不充裕?？蓱{據(jù)鍛件質(zhì)料、形狀和尺寸通過(guò)實(shí)驗(yàn)確定。

余熱等溫正火

⑴ 鑄造后鍛件溫度掌握。鍛件成形后的溫度必需在Ar3(對(duì)亞共析鋼)以上，鍛后零件溫度穩(wěn)定時(shí)可接納干脆急冷的方法;鍛后零件溫度顛簸較大或鍛件截面變更大時(shí)，必需增加均溫歷程，急冷前使零件溫度均勻一致，否則會(huì)造成急冷后鍛件或不同截面溫度相差大，產(chǎn)生非常構(gòu)造(貝氏體或馬氏體)。

⑵ 急冷冷卻速率掌握。急冷工序中要求鍛件快速冷卻，同時(shí)冷卻后統(tǒng)一鍛件和同批鍛件溫度均勻一致(或相近)。同時(shí)需求對(duì)急冷速率加以掌握，過(guò)快的急冷速率會(huì)在鍛件構(gòu)造中產(chǎn)生魏氏構(gòu)造。一般急冷速率掌握在30～42℃/min。

⑶ 急冷后溫度掌握。急冷后必需包管鍛件溫度在珠光體轉(zhuǎn)變區(qū)，不能低于貝氏體轉(zhuǎn)變開(kāi)始溫度(Bs)，否則構(gòu)造中會(huì)出現(xiàn)貝氏體(或粒狀貝氏體)構(gòu)造;如急冷后溫度過(guò)高會(huì)造成先共析鐵素體量增加，構(gòu)造轉(zhuǎn)變后珠光體片層間距大，造成零件硬度低。鍛件急冷后溫度一般掌握在質(zhì)料Bs溫度以上在80～100℃。

⑷ 等溫溫度的選定。等溫溫度的崎嶇干脆影響到等溫正火后鍛件的硬度，等溫溫度高則硬度低，等溫溫度低則硬度高。等溫溫度一般為鍛件質(zhì)料Bs溫度以上50～80℃，具體溫度需憑據(jù)鍛件的質(zhì)料、形狀經(jīng)實(shí)驗(yàn)進(jìn)行確定。

⑸ 等溫保溫時(shí)間確鑿定。珠光體轉(zhuǎn)變產(chǎn)生在等溫歷程中，是以必需有足夠的保溫時(shí)間，如等溫時(shí)間過(guò)短會(huì)造成過(guò)冷奧氏體沒(méi)有一切轉(zhuǎn)變?yōu)橹楣怏w，在隨后的冷卻歷程中轉(zhuǎn)變?yōu)樨愂象w或馬氏體，造成等溫處分后構(gòu)造分歧格和硬度高。等溫時(shí)間可憑據(jù)質(zhì)料的等溫轉(zhuǎn)變曲線進(jìn)行初步確定，并憑據(jù)實(shí)驗(yàn)情況進(jìn)行調(diào)整。

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Waste heat normalization (annealing)

(1) It is necessary to grasp the temperature before the forging is put into the furnace. When the temperature of the part is high, the forging is required to be blown to cool, so that the temperature of the part is lowered to the required normalizing temperature, and the power demand of the heat dividing furnace is sufficient, and heating is performed before the start of manufacturing and when the temperature of a small amount of forging is low.

(2) Determine the reasonable holding time. If the holding time is too long, the crystal grains will be thick and the holding time will be too short, which will cause the structural transformation to be insufficient. The material, shape and size of the forging can be determined experimentally.

Isothermal isotherm

(1) Master temperature of forging after casting. The temperature after forming the forging must be above Ar3 (for the sub-eutectoid steel). When the temperature of the forged part is stable, the method of quenching and quenching can be accepted. When the temperature of the forged part is large or the section of the forging is changed greatly, the temperature history must be increased. Make the temperature of the parts uniform before quenching, otherwise the forgings or different cross-section temperatures will be greatly different after quenching, resulting in very structural (bainite or martensite).

(2) The quenching cooling rate is mastered. In the quenching process, the forgings are required to be rapidly cooled, and at the same time, the uniform forgings and the same batch of forgings are uniformly uniform (or similar) after cooling. At the same time, the demand for the quenching rate is mastered, and the too fast quenching rate will produce the Wei's structure in the forging structure. Generally, the quenching rate is controlled at 30 to 42 ° C / min.

(3) Temperature control after quenching. After quenching, the forging temperature must be in the pearlite transformation zone, and should not be lower than the bainite transformation starting temperature (Bs). Otherwise, the bainite (or granular bainite) structure will appear in the structure; if the temperature is too high after quenching, it will cause The amount of ferrite is increased first, and the spacing of the pearlite sheets after the structural transformation is large, resulting in low hardness of the parts. After the forging is quenched, the temperature is generally above 80 ° C to 100 ° C above the Bs temperature.

(4) Selection of isothermal temperature. The roughness of the isothermal temperature simply affects the hardness of the forged part after isothermal normalizing, the hardness is low when the isothermal temperature is high, and the hardness is high when the isothermal temperature is low. The isothermal temperature is generally 50 to 80 ° C above the Bs temperature of the forging material. The specific temperature needs to be determined experimentally according to the material and shape of the forging.

(5) The isothermal holding time is fixed. The pearlite transformation occurs in the isothermal history, so it is necessary to have sufficient holding time. If the isothermal time is too short, the supercooled austenite will not be transformed into pearlite, and it will be transformed into bainite or horse in the subsequent cooling process. The body, causing the isothermal division to have a divergent lattice and a high hardness. The isothermal time can be initially determined by the isothermal transformation curve of the material and adjusted according to the experimental conditions.