1. The Introduction of Steel Grade
According to the standard of GB/T1228、1229、1230、1231, the production of ML20MnTiB sets of large hex highstrength bolts used in Steel Structure, and according to the standard of GB/T3632、3633 it uses sets of forswear type highstrength bolts.
The products are mainly used in railroad bridge, road bridge, boiler framework, long-span of industrial plants, civil high-rise buildings, all kinds of tower, light section steel structure, hoisting machinery and other Steel Structure links. Because of the application industry involves serious security problems referred to the national economy and the people's livelihood, the users pay close attention to the material quality.
2. Produce Conditions
XINGTAI STEEL began to research and develop this steel grade from October 2006. Through continuous refinement, now we have the ability to produce φ5.5mm－28mm.The majarity of customers are very satisfied with our quality.
3. Application Case
Now, we will give a brief introduction of service condition for φ22mm ML20MnTiB at one fastener company of Henan procince.
1.Manufacturer
This manufacturer is one of the biggest fastener companies in China, now, it is the company of standing director of China Fasteners Association with cold heading,hot heading, heattreatment , electroplate , hot-dip coating, flange and other production line, The main products are bolts, nuts, high strength bolt connection of steel construction , automotive fasteners, and non-standard products of customers need, which are sold at home and abroad, the annual production capacity is 6,000 tons.
2.Use Course
This company uses the productφ22mm ML20MnTiB of Xingtai Steel to produce grade 10.9 M22 outside Hex Bolts, the down user is a locomotive plant in Shanxi province Production process: annealing (780 ℃ heat 2.5 hours; down to 350 ℃ discharge ) - pickling, phosphorization- drawing (φ22 → φ21.4) - cold heading - thread rolling (perforated) - quenching (water quenching 880 ℃ ) - tempering(370 ℃) - flange - Inspection.
3.Results of Inspection
The manufacturer is very Satisfied with the index of chemical composition，hardness, tensile properties of products of Xingtai Steel. The machining process of pickling, drawing, cold heading, heat treatment, etc are very stable, which can meet the demands of customers.
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